Plants

20 pages, 1613 KiB

Open AccessEditor’s ChoiceReview

Integration of Abscisic Acid Signaling with Other Signaling Pathways in Plant Stress Responses and Development

by Manu Kumar, Mahipal Singh Kesawat, Asjad Ali, Sang-Choon Lee, Sarvajeet Singh Gill and Hyun Uk Kim

Plants 2019, 8(12), 592; https://doi.org/10.3390/plants8120592 - 11 Dec 2019

Cited by 85 | Viewed by 10656

Abstract

Plants are immobile and, to overcome harsh environmental conditions such as drought, salt, and cold, they have evolved complex signaling pathways. Abscisic acid (ABA), an isoprenoid phytohormone, is a critical signaling mediator that regulates diverse biological processes in various organisms. Significant progress has [...] Read more.

Plants are immobile and, to overcome harsh environmental conditions such as drought, salt, and cold, they have evolved complex signaling pathways. Abscisic acid (ABA), an isoprenoid phytohormone, is a critical signaling mediator that regulates diverse biological processes in various organisms. Significant progress has been made in the determination and characterization of key ABA-mediated molecular factors involved in different stress responses, including stomatal closure and developmental processes, such as seed germination and bud dormancy. Since ABA signaling is a complex signaling network that integrates with other signaling pathways, the dissection of its intricate regulatory network is necessary to understand the function of essential regulatory genes involved in ABA signaling. In the present review, we focus on two aspects of ABA signaling. First, we examine the perception of the stress signal (abiotic and biotic) and the response network of ABA signaling components that transduce the signal to the downstream pathway to respond to stress tolerance, regulation of stomata, and ABA signaling component ubiquitination. Second, ABA signaling in plant development processes, such as lateral root growth regulation, seed germination, and flowering time regulation is investigated. Examining such diverse signal integration dynamics could enhance our understanding of the underlying genetic, biochemical, and molecular mechanisms of ABA signaling networks in plants. Full article

(This article belongs to the Special Issue 2019 Feature Papers by Plants’ Editorial Board Members)

► Show Figures

Figure 1

14 pages, 1255 KiB

Open AccessEditor’s ChoiceReview

Arabidopsis WRKY53, a Node of Multi-Layer Regulation in the Network of Senescence

by Ulrike Zentgraf and Jasmin Doll

Plants 2019, 8(12), 578; https://doi.org/10.3390/plants8120578 - 6 Dec 2019

Cited by 43 | Viewed by 5016

Abstract

Leaf senescence is an integral part of plant development aiming at the remobilization of nutrients and minerals out of the senescing tissue into developing parts of the plant. Sequential as well as monocarpic senescence maximize the usage of nitrogen, mineral, and carbon resources [...] Read more.

Leaf senescence is an integral part of plant development aiming at the remobilization of nutrients and minerals out of the senescing tissue into developing parts of the plant. Sequential as well as monocarpic senescence maximize the usage of nitrogen, mineral, and carbon resources for plant growth and the sake of the next generation. However, stress-induced premature senescence functions as an exit strategy to guarantee offspring under long-lasting unfavorable conditions. In order to coordinate this complex developmental program with all kinds of environmental input signals, complex regulatory cues have to be in place. Major changes in the transcriptome imply important roles for transcription factors. Among all transcription factor families in plants, the NAC and WRKY factors appear to play central roles in senescence regulation. In this review, we summarize the current knowledge on the role of WRKY factors with a special focus on WRKY53. In contrast to a holistic multi-omics view we want to exemplify the complexity of the network structure by summarizing the multilayer regulation of WRKY53 of Arabidopsis. Full article

(This article belongs to the Special Issue Leaf Senescence)

► Show Figures

Figure 1

18 pages, 2094 KiB

Open AccessEditor’s ChoiceReview

Bacterium-Mediated RNA Interference: Potential Application in Plant Protection

by Simon Goodfellow, Daai Zhang, Ming-Bo Wang and Ren Zhang

Plants 2019, 8(12), 572; https://doi.org/10.3390/plants8120572 - 5 Dec 2019

Cited by 17 | Viewed by 7467

Abstract

RNAi has emerged as a promising tool for targeting agricultural pests and pathogens and could provide an environmentally friendly alternative to traditional means of control. However, the deployment of this technology is still limited by a lack of suitable exogenous- or externally applied [...] Read more.

RNAi has emerged as a promising tool for targeting agricultural pests and pathogens and could provide an environmentally friendly alternative to traditional means of control. However, the deployment of this technology is still limited by a lack of suitable exogenous- or externally applied delivery mechanisms. Numerous means of overcoming this limitation are being explored. One such method, bacterium-mediated RNA interference, or bmRNAi, has been explored in other systems and shows great potential for application to agriculture. Here, we review the current state of bmRNAi, examine the technical limitations and possible improvements, and discuss its potential applications in crop protection. Full article

(This article belongs to the Special Issue RNAs and Plant Disease Resistance)

► Show Figures

Figure 1

19 pages, 2523 KiB

Open AccessEditor’s ChoiceArticle

Optimize, Modulate, and Scale-up Resveratrol and Resveratrol Dimers Bioproduction in Vitis labrusca L. Cell Suspension from Flasks to 20 L Bioreactor

by Carole Lambert, Julien Lemaire, Hélène Auger, Arnaud Guilleret, Romain Reynaud, Christophe Clément, Eric Courot and Behnam Taidi

Plants 2019, 8(12), 567; https://doi.org/10.3390/plants8120567 - 4 Dec 2019

Cited by 23 | Viewed by 4170

Abstract

Resveratrol and its oligomers are biologically active compounds. This work brings new insights for the bioproduction of trans-resveratrol with three dimers, pallidol, trans-ε-viniferin, and trans-δ-viniferin, in cell suspension of Vitis labrusca. Conditions of elicitation by methyl jasmonate were optimized [...] Read more.

Resveratrol and its oligomers are biologically active compounds. This work brings new insights for the bioproduction of trans-resveratrol with three dimers, pallidol, trans-ε-viniferin, and trans-δ-viniferin, in cell suspension of Vitis labrusca. Conditions of elicitation by methyl jasmonate were optimized for the production of stilbenes using statistical design of experiment. Bio-production of stilbenes was scaled-up to 5 L and in these conditions, trans-resveratrol concentrations reached 237 mg/L, and for pallidol 114 mg/L. The comparison of different elicitation modes (different elicitors, combination with cyclodextrins or adsorbent resin) allowed to reach particularly high concentrations of target molecules: Resveratrol 6.14 g/L, pallidol 0.90 g/L, δ-viniferin 0.54 g/L, and ε-viniferin 0.50 g/L. Scale-up to 20 L-stirring-bioreactor gave similar growth rates to those observed in shake flask culture, with a high production of resveratrol (4.23 g/L) and δ-viniferin (0.76 g/L). This work provides new strategies for the production of stilbenes in plant cell suspension for biological and commercial evaluation. Full article

(This article belongs to the Special Issue Resveratrol in Plants)

► Show Figures

Figure 1

21 pages, 3718 KiB

Open AccessEditor’s ChoiceReview

Epigenetics Regulates Reproductive Development in Plants

by Qiang Han, Arthur Bartels, Xi Cheng, Angela Meyer, Yong-Qiang Charles An, Tzung-Fu Hsieh and Wenyan Xiao

Plants 2019, 8(12), 564; https://doi.org/10.3390/plants8120564 - 2 Dec 2019

Cited by 18 | Viewed by 8025

Abstract

Seed, resulting from reproductive development, is the main nutrient source for human beings, and reproduction has been intensively studied through genetic, molecular, and epigenetic approaches. However, how different epigenetic pathways crosstalk and integrate to regulate seed development remains unknown. Here, we review the [...] Read more.

Seed, resulting from reproductive development, is the main nutrient source for human beings, and reproduction has been intensively studied through genetic, molecular, and epigenetic approaches. However, how different epigenetic pathways crosstalk and integrate to regulate seed development remains unknown. Here, we review the recent progress of epigenetic changes that affect chromatin structure, such as DNA methylation, polycomb group proteins, histone modifications, and small RNA pathways in regulating plant reproduction. In gametogenesis of flowering plants, epigenetics is dynamic between the companion cell and gametes. Cytosine DNA methylation occurs in CG, CHG, CHH contexts (H = A, C, or T) of genes and transposable elements, and undergoes dynamic changes during reproduction. Cytosine methylation in the CHH context increases significantly during embryogenesis, reaches the highest levels in mature embryos, and decreases as the seed germinates. Polycomb group proteins are important transcriptional regulators during seed development. Histone modifications and small RNA pathways add another layer of complexity in regulating seed development. In summary, multiple epigenetic pathways are pivotal in regulating seed development. It remains to be elucidated how these epigenetic pathways interplay to affect dynamic chromatin structure and control reproduction. Full article

(This article belongs to the Section Plant Genetics, Genomics and Biotechnology)

► Show Figures

Graphical abstract

21 pages, 792 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Carotenoids in Cereal Food Crops: Composition and Retention throughout Grain Storage and Food Processing

by Daniela Trono

Plants 2019, 8(12), 551; https://doi.org/10.3390/plants8120551 - 28 Nov 2019

Cited by 48 | Viewed by 7326

Abstract

Carotenoids are C40 isoprenoids synthesized by plants, as well as some bacteria, fungi and algae, that have been reported to be responsible for a number of benefits conferred on human health. The inability of animals and humans to synthesize de novo these compounds [...] Read more.

Carotenoids are C40 isoprenoids synthesized by plants, as well as some bacteria, fungi and algae, that have been reported to be responsible for a number of benefits conferred on human health. The inability of animals and humans to synthesize de novo these compounds is the reason why they must be introduced from dietary sources. In cereal grains, carotenoids are important phytochemicals responsible for the characteristic yellow colour of the endosperm, which confers nutritional and aesthetic quality to cereal-based products. Cereals are staple foods for a large portion of the world population, and the biofortification of cereal grains with carotenoids may represent a simple way to prevent many human diseases and disorders. Unfortunately, evidence exists that the storage and processing of cereal grains into food products may negatively impact their carotenoid content; so, this loss should be taken into consideration when analysing the potential health benefits of the cereal-based products. Focusing on the recent updates, this review summarizes the chemical composition of the carotenoids in the grains of staple cereals, including wheat, maize, rice and sorghum, the main factors that affect their carotenoid content during storage and processing and the most fruitful strategies used improve the grain carotenoid content and limit the carotenoid post-harvest losses. Full article

(This article belongs to the Special Issue Carotenoid Biosynthesis, Regulation, Storage and Degradation in Plants)

► Show Figures

Figure 1

19 pages, 1207 KiB

Open AccessEditor’s ChoiceArticle

Polyphenol Compounds and Biological Activity of Caper (Capparis spinosa L.) Flowers Buds

by Aneta Wojdyło, Paulina Nowicka, Mar Grimalt, Pilar Legua, Maria Soledad Almansa, Asunción Amorós, Ángel Antonio Carbonell-Barrachina and Francisca Hernández

Plants 2019, 8(12), 539; https://doi.org/10.3390/plants8120539 - 25 Nov 2019

Cited by 44 | Viewed by 6124

Abstract

The aim of the study was to analyze potential health-promoting components of caper flower buds (Capparis spinosa L.) at six stages of development in two cultivars. Polyphenol compounds (flavonols, hydroxycinnamic acids, flavan-3-ols) were identified by Liquid Chromatography– quadrupole Time–of–Flight –Mass Spectrofotometer/Mass Spectrofotometer [...] Read more.

The aim of the study was to analyze potential health-promoting components of caper flower buds (Capparis spinosa L.) at six stages of development in two cultivars. Polyphenol compounds (flavonols, hydroxycinnamic acids, flavan-3-ols) were identified by Liquid Chromatography– quadrupole Time–of–Flight –Mass Spectrofotometer/Mass Spectrofotometer (LC-qTOF-MS/MS) and quantified by Ultra Performance Liquid Chromatography–Photodiode Array-Fluorescence Detector (UPLC-PDA-FL). Moreover, antioxidant properties (ABTS+•, FRAP, and ORAC), anti-diabetic potential (α-amylase and α-glucosidase), and anti-aging activity (acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)) of the buds were examined. Total phenolic compounds in the investigated caper varied from 10,720 to 3256 mg/100 g dry weight (DW), and depended on a genotype and growing stage of caper flowers. Among six different growing stages, the one named ‘nonpareilles’ was characterized by significantly higher content of polyphenols than the remaining five stages. The flavonols in caper flowers represented a mixture of different glycosylated quercetin, kaempferol, myricetin, and isorhamnetin derivatives, accounting for 38%–67%, 15%–36%, 4%–7%, and 0.8%–3%, respectively, of total flavonols,. Their contents strongly depended on the growth stage. ‘Nonpareilles’ and ‘surfines’ were richer in flavonols than ‘fines’ and ‘gruesas’. Of the six investigated growth stages, ‘nonpareilles’ accumulated the greatest amounts of bioactive compounds that correlated with antioxidant and anti-diabetic properties, and were more potent BuChE than AChE inhibitors. Full article

(This article belongs to the Section Phytochemistry)

► Show Figures

Figure 1

15 pages, 614 KiB

Open AccessEditor’s ChoiceArticle

First Report on Evaluation of Basic Nutritional and Antioxidant Properties of Moringa Oleifera Lam. from Caribbean Island of Saint Lucia

by Jozef Fejér, Ivan Kron, Vito Pellizzeri, Mária Pľuchtová, Adriana Eliašová, Luca Campone, Teresa Gervasi, Giovanni Bartolomeo, Nicola Cicero, Andrea Babejová, Mária Konečná, Vincent Sedlák, Janka Poráčová and Daniela Gruľová

Plants 2019, 8(12), 537; https://doi.org/10.3390/plants8120537 - 23 Nov 2019

Cited by 30 | Viewed by 5816

Abstract

Moringa oleifera Lam. has been considered as a multipurpose tree. The studies on it focus on its variable nutritional benefits. It is growing in many regions, but information about nutritional properties of those growing in the Caribbean is missing. The present study focused [...] Read more.

Moringa oleifera Lam. has been considered as a multipurpose tree. The studies on it focus on its variable nutritional benefits. It is growing in many regions, but information about nutritional properties of those growing in the Caribbean is missing. The present study focused on biochemical analysis of main nutritional and antioxidant properties in plant material—dried leaves and seeds—of Moringa oleifera. The composition of lipids, proteins, and vitamin E was evaluated in powdered dried leaves and seeds. Fatty acids were evaluated in oil extracted from the moringa seeds. Potential antioxidant properties of the moringa were evaluated in extract from crushed and powdered leaves, as well as from the powdered seeds. The total amounts of lipids, proteins, and vitamin E were higher in powdered seeds (31.85%, 35.13%, and 220.61 mg/kg) than in powdered leaves (12.48%, 20.54%, and 178.10 mg/kg). The main compound of fatty acids presented oleic acid (76.78%) in seeds’ oil and oleic (25.01%), palmitic (24.84%), and linolenic (24.71%) acids in leaves. Neohesperidin (126.8 mg/kg), followed by chlorogenic acid (99.96 mg/kg) and quercetin (43.44 and 21.44 mg/kg) were main phenolic compounds identified. Total phenols in powdered leaves’ extract (635.6 mg GAE/L) was higher than in powdered seeds’ extract (229.5 mg GAE/L). The activity against superoxide radical and hydroxyl radical was 92.4% and 73.1% by leaves’ powder extract and 83.6% and 60.7% by crushed-leaf extract; seed-powder extract exhibited a pro-oxidation activity (−68.4%) against superoxide radical and the lowest antioxidant effect against the hydroxyl radical (55.0%). Full article

► Show Figures

Graphical abstract

15 pages, 623 KiB

Open AccessEditor’s ChoiceArticle

Plant-Based Biostimulants Influence the Agronomical, Physiological, and Qualitative Responses of Baby Rocket Leaves under Diverse Nitrogen Conditions

by Ida Di Mola, Lucia Ottaiano, Eugenio Cozzolino, Mauro Senatore, Maria Giordano, Christophe El-Nakhel, Adriana Sacco, Youssef Rouphael, Giuseppe Colla and Mauro Mori

Plants 2019, 8(11), 522; https://doi.org/10.3390/plants8110522 - 19 Nov 2019

Cited by 81 | Viewed by 5369

Abstract

Nitrogen is the primary technical means responsible for food production increase, but on the other hand, wise management is needed because its excessive use can have a negative impact on the environment and on green leafy vegetable quality, such as that rocket. Rocket [...] Read more.

Nitrogen is the primary technical means responsible for food production increase, but on the other hand, wise management is needed because its excessive use can have a negative impact on the environment and on green leafy vegetable quality, such as that rocket. Rocket has the characteristics of accumulating nitrate in leaves with possible impacts on human health. In order to overcome this issue, researchers are focusing their attention on the use of alternative means, such as plant biostimulant application. The scope of this study was to assess the effect of legume-derived protein hydrolysate(LDPH) and tropical plant extract(TPE), combined with various doses of nitrogen (0 kg ha⁻¹ non-fertilized; N0); 60 kg ha⁻¹ (sub-optimal; N1); 80 kg ha⁻¹ (optimal; N2); and 100 kg ha⁻¹ (supra-optimal; N3)), in order to reduce nitrogen use, boost yield, and enhance the chemical and nutritional value of leaves without significantly accumulating nitrate. Both vegetal-based plant biostimulants enhanced plant growth, boosted the marketable yield (especially at N0 and N1 levels, by 38.2% and 28.2%, respectively, compared to the non-treated control), and increased the SPAD (Soil Plant Analysis Development) index and leaf pigments content, such as chlorophyll and carotenoids, especially in treated-LDPH rocket. The plant-based biostimulants also produced a major amplification in lipophilic antioxidant activity (+ 48%) and total ascorbic acid content (average + 95.6%), especially at low nitrogen fertilization levels, and maintained nitrate content under the legal European Comission limits. Full article

(This article belongs to the Special Issue Factors Affecting Yield, Quality, Antioxidants, Mineral Composition and Residual Biomass Valorization of Vegetable Crops)

► Show Figures

Figure 1

11 pages, 816 KiB

Open AccessEditor’s ChoiceReview

Glyphosate: Its Environmental Persistence and Impact on Crop Health and Nutrition

by Ramdas Kanissery, Biwek Gairhe, Davie Kadyampakeni, Ozgur Batuman and Fernando Alferez

Plants 2019, 8(11), 499; https://doi.org/10.3390/plants8110499 - 13 Nov 2019

Cited by 144 | Viewed by 22918

Abstract

Glyphosate-based herbicide products are the most widely used broad-spectrum herbicides in the world for postemergent weed control. There are ever-increasing concerns that glyphosate, if not used judiciously, may cause adverse nontarget impacts in agroecosystems. The purpose of this brief review is to present [...] Read more.

Glyphosate-based herbicide products are the most widely used broad-spectrum herbicides in the world for postemergent weed control. There are ever-increasing concerns that glyphosate, if not used judiciously, may cause adverse nontarget impacts in agroecosystems. The purpose of this brief review is to present and discuss the state of knowledge with respect to its persistence in the environment, possible effects on crop health, and impacts on crop nutrition. Full article

(This article belongs to the Section Plant Protection and Biotic Interactions)

► Show Figures

Figure 1

12 pages, 1972 KiB

Open AccessEditor’s ChoiceArticle

Highly Predictive Genetic Markers Distinguish Drug-Type from Fiber-Type Cannabis sativa L

by Fidelia Cascini, Alessio Farcomeni, Daniele Migliorini, Laura Baldassarri, Ilaria Boschi, Simona Martello, Stefano Amaducci, Luigi Lucini and Jamila Bernardi

Plants 2019, 8(11), 496; https://doi.org/10.3390/plants8110496 - 12 Nov 2019

Cited by 30 | Viewed by 5573

Abstract

Genetic markers can be used in seeds and in plants to distinguish drug-type from fiber-type Cannabis Sativa L. varieties even at early stages, including pre-germination when cannabinoids are not accumulated yet. With this aim, this paper reports sequencing results for tetrahydrocannabinolic acid synthase [...] Read more.

Genetic markers can be used in seeds and in plants to distinguish drug-type from fiber-type Cannabis Sativa L. varieties even at early stages, including pre-germination when cannabinoids are not accumulated yet. With this aim, this paper reports sequencing results for tetrahydrocannabinolic acid synthase (THCAS) and cannabidiolic acid synthase (CBDAS) genes from 21 C. sativa L. varieties. Taking into account that THCAS- and CBDAS-derived enzymes compete for the same substrate, the novelty of this work relies in the identification of markers based on both THCAS and CBDAS rather than THCAS alone. Notably, in our panel, we achieved an adequate degree of discrimination (AUC 100%) between drug-type and fiber-type cannabis samples. Our sequencing approach allowed identifying multiple genetic markers (single-nucleotide polymorphisms—SNPs—and a deletion/insertion) that effectively discriminate between the two subgroups of cannabis, namely fiber type vs. drug type. We identified four functional SNPs that are likely to induce decreased THCAS activity in the fiber-type cannabis plants. We also report the finding on a deletion in the CBDAS gene sequence that produces a truncated protein, possibly resulting in loss of function of the enzyme in the drug-type varieties. Chemical analyses for the actual concentration of cannabinoids confirmed the identification of drug-type rather than fiber-type genotypes. Genetic markers permit an early identification process for forensic applications while simplifying the procedures related to detection of therapeutic or industrial hemp. Full article

(This article belongs to the Section Plant Genetics, Genomics and Biotechnology)

► Show Figures

Graphical abstract

22 pages, 6398 KiB

Open AccessEditor’s ChoiceReview

Plant Disease Detection and Classification by Deep Learning

by Muhammad Hammad Saleem, Johan Potgieter and Khalid Mahmood Arif

Plants 2019, 8(11), 468; https://doi.org/10.3390/plants8110468 - 31 Oct 2019

Cited by 414 | Viewed by 70759

Abstract

Plant diseases affect the growth of their respective species, therefore their early identification is very important. Many Machine Learning (ML) models have been employed for the detection and classification of plant diseases but, after the advancements in a subset of ML, that is, [...] Read more.

Plant diseases affect the growth of their respective species, therefore their early identification is very important. Many Machine Learning (ML) models have been employed for the detection and classification of plant diseases but, after the advancements in a subset of ML, that is, Deep Learning (DL), this area of research appears to have great potential in terms of increased accuracy. Many developed/modified DL architectures are implemented along with several visualization techniques to detect and classify the symptoms of plant diseases. Moreover, several performance metrics are used for the evaluation of these architectures/techniques. This review provides a comprehensive explanation of DL models used to visualize various plant diseases. In addition, some research gaps are identified from which to obtain greater transparency for detecting diseases in plants, even before their symptoms appear clearly. Full article

► Show Figures

Figure 1

13 pages, 1584 KiB

Open AccessEditor’s ChoiceArticle

Improvement of Phenolic Compounds, Essential Oil Content and Antioxidant Properties of Sweet Basil (Ocimum basilicum L.) Depending on Type and Concentration of Selenium Application

by Liubov Skrypnik, Anastasia Novikova and Elina Tokupova

Plants 2019, 8(11), 458; https://doi.org/10.3390/plants8110458 - 29 Oct 2019

Cited by 57 | Viewed by 6590

Abstract

The effect of selenium biofortification on phytomass yield, selenium, essential oil and phenolic compounds content as well as antioxidant properties of basil leaves was investigated. Selenium in form of sodium selenate was applied either in nutrient solution or by foliar spraying at three [...] Read more.

The effect of selenium biofortification on phytomass yield, selenium, essential oil and phenolic compounds content as well as antioxidant properties of basil leaves was investigated. Selenium in form of sodium selenate was applied either in nutrient solution or by foliar spraying at three levels (2.0, 5.0 and 10.0 μM). Selenium treatment significantly increased Se concentration in leaves up to 20.23 μg g⁻¹ (addition in nutrient solution) and 10.74 μg g⁻¹ (foliar application). Neither a toxic nor a beneficial effect of Se addition on the plants was observed. Se application of 2 µM Se in nutrient solution and of 5 µM Se by foliar spraying successfully enhanced production of essential oils, hydroxycinnamic acids, total phenolics and antioxidant activity of basil leaves. The anthocyanin content was positively affected only by application of Se in nutrient solution. Considering both an increase in the Se concentration in basil leaves and an increase in the production of phytonutrients, the optimal doses of selenium can be considered to be 5 and 10 μM for Se addition in nutrient solution and by foliar treatment, respectively. The results confirm the possibility of the enrichment of basil plants with selenium and thereby improving the nutritional qualities of the human diet. Full article

(This article belongs to the Special Issue Selenium Metabolism and Accumulation in Plants)

► Show Figures

Graphical abstract

11 pages, 1060 KiB

Open AccessEditor’s ChoiceReview

Silicon and Plant Natural Defenses against Insect Pests: Impact on Plant Volatile Organic Compounds and Cascade Effects on Multitrophic Interactions

by Nicolas Leroy, Félix de Tombeur, Yseult Walgraffe, Jean-Thomas Cornélis and François J. Verheggen

Plants 2019, 8(11), 444; https://doi.org/10.3390/plants8110444 - 23 Oct 2019

Cited by 45 | Viewed by 9978

Abstract

Environmental factors controlling silicon (Si) accumulation in terrestrial plant are key drivers to alleviate plant biotic stresses, including insect herbivory. While there is a general agreement on the ability of Si-enriched plant to better resist insect feeding, recent studies suggest that Si also [...] Read more.

Environmental factors controlling silicon (Si) accumulation in terrestrial plant are key drivers to alleviate plant biotic stresses, including insect herbivory. While there is a general agreement on the ability of Si-enriched plant to better resist insect feeding, recent studies suggest that Si also primes biochemical defense pathways in various plant families. In this review, we first summarize how soil parameters and climate variables influence Si assimilation in plants. Then, we describe recent evidences on the ability of Si to modulate plant volatile emissions, with potential cascade effects on phytophagous insects and higher trophic levels. Even though the mechanisms still need to be elucidated, Si accumulation in plants leads to contrasting effects on the levels of the three major phytohormones, namely jasmonic acid, salicylic acid and ethylene, resulting in modified emissions of plant volatile organic compounds. Herbivore-induced plant volatiles would be particularly impacted by Si concentration in plant tissues, resulting in a cascade effect on the attraction of natural enemies of pests, known to locate their prey or hosts based on plant volatile cues. Since seven of the top 10 most important crops in the world are Si-accumulating Poaceae species, it is important to discuss the potential of Si mobility in soil-plant systems as a novel component of an integrated pest management. Full article

(This article belongs to the Special Issue The Role of Silicon in Plant Defences)

► Show Figures

Figure 1

19 pages, 1857 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Coordination of Leaf Development Across Developmental Axes

by James W. Satterlee and Michael J. Scanlon

Plants 2019, 8(10), 433; https://doi.org/10.3390/plants8100433 - 22 Oct 2019

Cited by 21 | Viewed by 10211

Abstract

Leaves are initiated as lateral outgrowths from shoot apical meristems throughout the vegetative life of the plant. To achieve proper developmental patterning, cell-type specification and growth must occur in an organized fashion along the proximodistal (base-to-tip), mediolateral (central-to-edge), and adaxial–abaxial (top-bottom) axes of [...] Read more.

Leaves are initiated as lateral outgrowths from shoot apical meristems throughout the vegetative life of the plant. To achieve proper developmental patterning, cell-type specification and growth must occur in an organized fashion along the proximodistal (base-to-tip), mediolateral (central-to-edge), and adaxial–abaxial (top-bottom) axes of the developing leaf. Early studies of mutants with defects in patterning along multiple leaf axes suggested that patterning must be coordinated across developmental axes. Decades later, we now recognize that a highly complex and interconnected transcriptional network of patterning genes and hormones underlies leaf development. Here, we review the molecular genetic mechanisms by which leaf development is coordinated across leaf axes. Such coordination likely plays an important role in ensuring the reproducible phenotypic outcomes of leaf morphogenesis. Full article

(This article belongs to the Special Issue From Genes to Shape and Function: Leaf Morphogenesis at Play)

► Show Figures

Figure 1

16 pages, 888 KiB

Open AccessEditor’s ChoiceReview

Potassium in Root Growth and Development

by Marek Sustr, Ales Soukup and Edita Tylova

Plants 2019, 8(10), 435; https://doi.org/10.3390/plants8100435 - 22 Oct 2019

Cited by 120 | Viewed by 11719

Abstract

Potassium is an essential macronutrient that has been partly overshadowed in root science by nitrogen and phosphorus. The current boom in potassium-related studies coincides with an emerging awareness of its importance in plant growth, metabolic functions, stress tolerance, and efficient agriculture. In this [...] Read more.

Potassium is an essential macronutrient that has been partly overshadowed in root science by nitrogen and phosphorus. The current boom in potassium-related studies coincides with an emerging awareness of its importance in plant growth, metabolic functions, stress tolerance, and efficient agriculture. In this review, we summarized recent progress in understanding the role of K⁺ in root growth, development of root system architecture, cellular functions, and specific plant responses to K⁺ shortage. K⁺ transport is crucial for its physiological role. A wide range of K⁺ transport proteins has developed during evolution and acquired specific functions in plants. There is evidence linking K⁺ transport with cell expansion, membrane trafficking, auxin homeostasis, cell signaling, and phloem transport. This places K⁺ among important general regulatory factors of root growth. K⁺ is a rather mobile element in soil, so the absence of systemic and localized root growth response has been accepted. However, recent research confirms both systemic and localized growth response in Arabidopsis thaliana and highlights K⁺ uptake as a crucial mechanism for plant stress response. K⁺-related regulatory mechanisms, K⁺ transporters, K⁺ acquisition efficiency, and phenotyping for selection of K⁺ efficient plants/cultivars are highlighted in this review. Full article

(This article belongs to the Special Issue Root System Structure and Function: A Themed Issue in Honor of Professor Yoav Waisel)

► Show Figures

Figure 1

13 pages, 641 KiB

Open AccessEditor’s ChoiceReview

Heterophylly: Phenotypic Plasticity of Leaf Shape in Aquatic and Amphibious Plants

by Gaojie Li, Shiqi Hu, Hongwei Hou and Seisuke Kimura

Plants 2019, 8(10), 420; https://doi.org/10.3390/plants8100420 - 16 Oct 2019

Cited by 51 | Viewed by 18039

Abstract

Leaves show great diversity in shape, size, and color in nature. Interestingly, many plant species have the ability to alter their leaf shape in response to their surrounding environment. This phenomenon is termed heterophylly, and is thought to be an adaptive feature to [...] Read more.

Leaves show great diversity in shape, size, and color in nature. Interestingly, many plant species have the ability to alter their leaf shape in response to their surrounding environment. This phenomenon is termed heterophylly, and is thought to be an adaptive feature to environmental heterogeneity in many cases. Heterophylly is widespread among land plants, and is especially dominant in aquatic and amphibious plants. Revealing the mechanisms underlying heterophylly would provide valuable insight into the interaction between environmental conditions and plant development. Here, we review the history and recent progress of research on heterophylly in aquatic and amphibious plants. Full article

(This article belongs to the Special Issue From Genes to Shape and Function: Leaf Morphogenesis at Play)

► Show Figures

Figure 1

16 pages, 351 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Non-Target-Site Resistance to Herbicides: Recent Developments

by Mithila Jugulam and Chandrima Shyam

Plants 2019, 8(10), 417; https://doi.org/10.3390/plants8100417 - 15 Oct 2019

Cited by 107 | Viewed by 7210

Abstract

Non-target-site resistance (NTSR) to herbicides in weeds can be conferred as a result of the alteration of one or more physiological processes, including herbicide absorption, translocation, sequestration, and metabolism. The mechanisms of NTSR are generally more complex to decipher than target-site resistance (TSR) [...] Read more.

Non-target-site resistance (NTSR) to herbicides in weeds can be conferred as a result of the alteration of one or more physiological processes, including herbicide absorption, translocation, sequestration, and metabolism. The mechanisms of NTSR are generally more complex to decipher than target-site resistance (TSR) and can impart cross-resistance to herbicides with different modes of action. Metabolism-based NTSR has been reported in many agriculturally important weeds, although reduced translocation and sequestration of herbicides has also been found in some weeds. This review focuses on summarizing the recent advances in our understanding of the physiological, biochemical, and molecular basis of NTSR mechanisms found in weed species. Further, the importance of examining the co-existence of TSR and NTSR for the same herbicide in the same weed species and influence of environmental conditions in the altering and selection of NTSR is also discussed. Knowledge of the prevalence of NTSR mechanisms and co-existing TSR and NTSR in weeds is crucial for designing sustainable weed management strategies to discourage the further evolution and selection of herbicide resistance in weeds. Full article

(This article belongs to the Special Issue Herbicide Resistance in Plants)

28 pages, 1259 KiB

Open AccessEditor’s ChoiceReview

Transcription Factors Associated with Leaf Senescence in Crops

by Sofia Bengoa Luoni, Francisco H. Astigueta, Salvador Nicosia, Sebastian Moschen, Paula Fernandez and Ruth Heinz

Plants 2019, 8(10), 411; https://doi.org/10.3390/plants8100411 - 14 Oct 2019

Cited by 46 | Viewed by 7368

Abstract

Leaf senescence is a complex mechanism controlled by multiple genetic and environmental variables. Different crops present a delay in leaf senescence with an important impact on grain yield trough the maintenance of the photosynthetic leaf area during the reproductive stage. Additionally, because of [...] Read more.

Leaf senescence is a complex mechanism controlled by multiple genetic and environmental variables. Different crops present a delay in leaf senescence with an important impact on grain yield trough the maintenance of the photosynthetic leaf area during the reproductive stage. Additionally, because of the temporal gap between the onset and phenotypic detection of the senescence process, candidate genes are key tools to enable the early detection of this process. In this sense and given the importance of some transcription factors as hub genes in senescence pathways, we present a comprehensive review on senescence-associated transcription factors, in model plant species and in agronomic relevant crops. This review will contribute to the knowledge of leaf senescence process in crops, thus providing a valuable tool to assist molecular crop breeding. Full article

(This article belongs to the Special Issue Leaf Senescence)

► Show Figures

Figure 1

19 pages, 2832 KiB

Open AccessEditor’s ChoiceArticle

UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil

by Haana Mosadegh, Alice Trivellini, Mariella Lucchesini, Antonio Ferrante, Rita Maggini, Paolo Vernieri and Anna Mensuali Sodi

Plants 2019, 8(10), 396; https://doi.org/10.3390/plants8100396 - 4 Oct 2019

Cited by 32 | Viewed by 5497

Abstract

UV-B radiation has been previously reported to induce protective or deleterious effects on plants depending on the UV-B irradiation doses. To elucidate how these contrasting events are physiologically coordinated, we exposed sweet basil plants to two UV-B doses: low (8.5 kJ m⁻² [...] Read more.

UV-B radiation has been previously reported to induce protective or deleterious effects on plants depending on the UV-B irradiation doses. To elucidate how these contrasting events are physiologically coordinated, we exposed sweet basil plants to two UV-B doses: low (8.5 kJ m⁻² day⁻¹, 30 min exposure) and high (68 kJ m⁻² day⁻¹, 4 h exposure), with the plants given both doses once continuously in a single day. Physiological tests during and after both UV-B exposures were performed by comparing the stress-induced damage and adverse effects on photosynthetic activity, the concentration and composition of photosynthetic and non-photosynthetic pigments, and stress-related hormones biosynthesis in basil plants. Our results showed that upon receiving a high UV-B dose, a severe inactivation of oxygen evolving complex (OEC) activity at the PSII donor side and irreversible PSII photodamage caused primarily by limitation of the acceptor side occurred, which overloaded protective mechanisms and finally led to the death of the plants. In contrast, low UV-B levels did not induce any signs of UV-B stress injuries. The OEC partial limitation and the inactivation of the electron transport chain allowed the activation of photoprotective mechanisms, avoiding irreversible damage to PSII. Overall results indicate the importance of a specific response mechanisms regulating photoprotection vs irreversible photoinhibition in basil that were modulated depending on the UV-B doses. Full article

► Show Figures

Figure 1

20 pages, 8079 KiB

Open AccessEditor’s ChoiceArticle

Magnesium-Deficiency Effects on Pigments, Photosynthesis and Photosynthetic Electron Transport of Leaves, and Nutrients of Leaf Blades and Veins in Citrus sinensis Seedlings

by Xin Ye, Xu-Feng Chen, Chong-Ling Deng, Lin-Tong Yang, Ning-Wei Lai, Jiu-Xin Guo and Li-Song Chen

Plants 2019, 8(10), 389; https://doi.org/10.3390/plants8100389 - 30 Sep 2019

Cited by 51 | Viewed by 7874

Abstract

Citrus sinensis seedlings were irrigated with nutrient solution at a concentration of 0 (Mg-deficiency) or 2 (Mg-sufficiency) mM Mg (NO₃)₂ for 16 weeks. Mg-deficiency-induced interveinal chlorosis, vein enlargement and corkiness, and alterations of gas exchange, pigments, chlorophyll a fluorescence (OJIP) [...] Read more.

Citrus sinensis seedlings were irrigated with nutrient solution at a concentration of 0 (Mg-deficiency) or 2 (Mg-sufficiency) mM Mg (NO₃)₂ for 16 weeks. Mg-deficiency-induced interveinal chlorosis, vein enlargement and corkiness, and alterations of gas exchange, pigments, chlorophyll a fluorescence (OJIP) transients and related parameters were observed in middle and lower leaves, especially in the latter, but not in upper leaves. Mg-deficiency might impair the whole photosynthetic electron transport, including structural damage to thylakoids, ungrouping of photosystem II (PSII), inactivation of oxygen-evolving complex (OEC) and reaction centers (RCs), increased reduction of primary quinone electron acceptor (Q_A) and plastoquinone pool at PSII acceptor side and oxidation of PSI end-electron acceptors, thus lowering energy transfer and absorption efficiency and the transfer of electrons to the dark reactions, hence, the rate of CO₂ assimilation in Mg-deficiency middle and lower leaves. Although potassium, Mg, manganese and zinc concentration in blades displayed a significant and positive relationship with the corresponding element concentration in veins, respectively, great differences existed in Mg-deficiency-induced alterations of nutrient concentrations between leaf blades and veins. For example, Mg-deficiency increased boron level in the blades of upper leaves, decreased boron level in the blades of lower leaves, but did not affect boron level in the blades of middle leaves and veins of upper, middle and lower leaves. To conclude, Mg-deficiency-induced interveinal chlorosis, vein enlargement, and corkiness, and alterations to photosynthesis and related parameters increased with increasing leaf age. Mg-deficiency-induced enlargement and corkiness of veins were not caused by Mg-deficiency-induced boron-starvation. Full article

(This article belongs to the Special Issue Advances in Citrus Research)

► Show Figures

Figure 1

19 pages, 524 KiB

Open AccessEditor’s ChoiceArticle

Antimicrobial Activity, Antioxidant Potential, Cytotoxicity and Phytochemical Profiling of Four Plants Locally Used against Skin Diseases

by John A. Asong, Stephen O. Amoo, Lyndy J. McGaw, Sanah M. Nkadimeng, Adeyemi O. Aremu and Wilfred Otang-Mbeng

Plants 2019, 8(9), 350; https://doi.org/10.3390/plants8090350 - 15 Sep 2019

Cited by 35 | Viewed by 5791

Abstract

Although orthodox medications are available for skin diseases, expensive dermatological services have necessitated the use of medicinal plants as a cheaper alternative. This study evaluated the pharmacological and phytochemical profiles of four medicinal plants (Drimia sanguinea, Elephantorrhiza elephantina, Helichrysum paronychioides [...] Read more.

Although orthodox medications are available for skin diseases, expensive dermatological services have necessitated the use of medicinal plants as a cheaper alternative. This study evaluated the pharmacological and phytochemical profiles of four medicinal plants (Drimia sanguinea, Elephantorrhiza elephantina, Helichrysum paronychioides, and Senecio longiflorus) used for treating skin diseases. Petroleum ether and 50% methanol extracts of the plants were screened for antimicrobial activity against six microbes: Bacillus cereus, Shigella flexneri, Candida glabrata, Candida krusei, Trichophyton rubrum and Trichophyton tonsurans using the micro-dilution technique. Antioxidant activity was conducted using 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging and β-carotene linoleic acid models. Cytotoxicity was determined against African green monkey Vero kidney cells based on the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. Spectrophotometric and Gas Chromatography-Mass Spectrometry (GC-MS) methods were used to evaluate the phytochemical constituents. All the extracts demonstrated varying degrees of antimicrobial potencies. Shigella flexneri, Candida glabrata, Trichophyton rubrum and Trichophyton tonsurans were most susceptible at 0.10 mg/mL. In the DPPH test, EC₅₀ values ranged from approximately 6–93 µg/mL and 65%–85% antioxidant activity in the β-carotene linoleic acid antioxidant activity model. The phenolic and flavonoid contents ranged from 3.5–64 mg GAE/g and 1.25–28 mg CE/g DW, respectively. The LC₅₀ values of the cytotoxicity assay ranged from 0.015–5622 µg/mL. GC-MS analysis revealed a rich pool (94–198) of bioactive compounds including dotriacontane, benzothiazole, heptacosane, bumetrizole, phthalic acid, stigmasterol, hexanoic acid and eicosanoic acid, which were common to the four plants. The current findings provide some degree of scientific evidence supporting the use of these four plants in folk medicine. However, the plants with high cytotoxicity need to be used with caution. Full article

(This article belongs to the Section Phytochemistry)

► Show Figures

Graphical abstract

19 pages, 3580 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Role of the Antioxidant System and the Tetrapyrrole Cycle in Iron Deficiency Chlorosis

by Carla S. Santos, Rengin Ozgur, Baris Uzilday, Ismail Turkan, Mariana Roriz, António O.S.S. Rangel, Susana M.P. Carvalho and Marta W. Vasconcelos

Plants 2019, 8(9), 348; https://doi.org/10.3390/plants8090348 - 13 Sep 2019

Cited by 43 | Viewed by 4963

Abstract

Iron deficiency chlorosis (IDC) is an abiotic stress often experienced by soybean, owing to the low solubility of iron in alkaline soils. Here, soybean lines with contrasting Fe efficiencies were analyzed to test the hypothesis that the Fe efficiency trait is linked to [...] Read more.

Iron deficiency chlorosis (IDC) is an abiotic stress often experienced by soybean, owing to the low solubility of iron in alkaline soils. Here, soybean lines with contrasting Fe efficiencies were analyzed to test the hypothesis that the Fe efficiency trait is linked to antioxidative stress signaling via proper management of tissue Fe accumulation and transport, which in turn influences the regulation of heme and non heme containing enzymes involved in Fe uptake and ROS scavenging. Inefficient plants displayed higher oxidative stress and lower ferric reductase activity, whereas root and leaf catalase activity were nine-fold and three-fold higher, respectively. Efficient plants do not activate their antioxidant system because there is no formation of ROS under iron deficiency; while inefficient plants are not able to deal with ROS produced under iron deficiency because ascorbate peroxidase and superoxide dismutase are not activated because of the lack of iron as a cofactor, and of heme as a constituent of those enzymes. Superoxide dismutase and peroxidase isoenzymatic regulation may play a determinant role: 10 superoxide dismutase isoenzymes were observed in both cultivars, but iron superoxide dismutase activity was only detected in efficient plants; 15 peroxidase isoenzymes were observed in the roots and trifoliate leaves of efficient and inefficient cultivars and peroxidase activity levels were only increased in roots of efficient plants. Full article

(This article belongs to the Special Issue ROS Responses in Plants)

► Show Figures

Graphical abstract

18 pages, 3943 KiB

Open AccessEditor’s ChoiceReview

Current Status and Future Prospects in Herbicide Discovery

by Franck E. Dayan

Plants 2019, 8(9), 341; https://doi.org/10.3390/plants8090341 - 11 Sep 2019

Cited by 151 | Viewed by 16707

Abstract

Herbicides represent about 60% of the pesticides (by volume) used worldwide. The success of herbicides can be attributed in part to a relatively steady discovery of one unique mechanisms of action (MOA) every two years from the early 1950s to the mid-1980s. While [...] Read more.

Herbicides represent about 60% of the pesticides (by volume) used worldwide. The success of herbicides can be attributed in part to a relatively steady discovery of one unique mechanisms of action (MOA) every two years from the early 1950s to the mid-1980s. While this situation changed dramatically after the introduction of glyphosate-resistant crops, evolution of resistance to glyphosate has renewed the agrichemical industry interest in new chemistry interacting with novel target sites. This review analyses recent characterization of new herbicide target sites, the chemical classes developed to inhibit these target sites, and where appropriate the innovative technologies used in these discovery programs. Full article

(This article belongs to the Special Issue Herbicide Resistance in Plants)

► Show Figures

Graphical abstract

9 pages, 2279 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Herbicide Resistance Traits in Maize and Soybean: Current Status and Future Outlook

by Vijay K. Nandula

Plants 2019, 8(9), 337; https://doi.org/10.3390/plants8090337 - 9 Sep 2019

Cited by 52 | Viewed by 7795

Abstract

This article reviews, focusing on maize and soybean, previous efforts to develop nontransgenic herbicide-resistant crops (HRCs), currently available transgenic HRC traits and technologies, as well as future chemical weed management options over the horizon. Since the mid twentieth century, herbicides rapidly replaced all [...] Read more.

This article reviews, focusing on maize and soybean, previous efforts to develop nontransgenic herbicide-resistant crops (HRCs), currently available transgenic HRC traits and technologies, as well as future chemical weed management options over the horizon. Since the mid twentieth century, herbicides rapidly replaced all other means of weed management. Overreliance on ‘herbicide-only’ weed control strategies hastened evolution of HR weed species. Glyphosate-resistant (GR) crop technology revolutionized weed management in agronomic crops, but GR weeds, led by Palmer amaranth, severely reduced returns from various cropping systems and affected the bottom line of growers across the world. An additional problem was the lack of commercialization of a new herbicide mode of action since the 1990s. Auxinic HRCs offer a short-term alternative for management of GR Palmer amaranth and other weed species. New HRCs stacked with multiple herbicide resistance traits and at least two new herbicide modes of action expected to be available in the mid-2020s provide new chemical options for weed management in row crops in the next decade. Full article

(This article belongs to the Special Issue Herbicide Resistance in Plants)

► Show Figures

Figure 1

19 pages, 1835 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Jasmonates—the Master Regulator of Rice Development, Adaptation and Defense

by Hieu Trang Nguyen, Huong Thi Mai To, Michel Lebrun, Stephane Bellafiore and Antony Champion

Plants 2019, 8(9), 339; https://doi.org/10.3390/plants8090339 - 9 Sep 2019

Cited by 39 | Viewed by 7311

Abstract

Rice is one of the most important food crops worldwide, as well as the model plant in molecular studies on the cereals group. Many different biotic and abiotic agents often limit rice production and threaten food security. Understanding the molecular mechanism, by which [...] Read more.

Rice is one of the most important food crops worldwide, as well as the model plant in molecular studies on the cereals group. Many different biotic and abiotic agents often limit rice production and threaten food security. Understanding the molecular mechanism, by which the rice plant reacts and resists these constraints, is the key to improving rice production to meet the demand of an increasing population. The phytohormone jasmonic acid (JA) and related compounds, collectively called jasmonates, are key regulators in plant growth and development. They are also one of the central players in plant immunity against biotic attacks and adaptation to unfavorable environmental conditions. Here, we review the most recent knowledge about jasmonates signaling in the rice crop model. We highlight the functions of jasmonates signaling in many adaptive responses, and also in rice growth and development processes. We also draw special attention to different signaling modules that are controlled by jasmonates in rice. Full article

(This article belongs to the Special Issue The Jasmonate Pathway: New Actors, Mechanisms and Impacts)

► Show Figures

Figure 1

18 pages, 676 KiB

Open AccessEditor’s ChoiceReview

Regulation of Symbiotic Nitrogen Fixation in Legume Root Nodules

by Andrés R. Schwember, Joachim Schulze, Alejandro del Pozo and Ricardo A. Cabeza

Plants 2019, 8(9), 333; https://doi.org/10.3390/plants8090333 - 6 Sep 2019

Cited by 63 | Viewed by 13557

Abstract

In most legume nodules, the di-nitrogen (N₂)-fixing rhizobia are present as organelle-like structures inside their root host cells. Many processes operate and interact within the symbiotic relationship between plants and nodules, including nitrogen (N)/carbon (C) metabolisms, oxygen flow through nodules, oxidative [...] Read more.

In most legume nodules, the di-nitrogen (N₂)-fixing rhizobia are present as organelle-like structures inside their root host cells. Many processes operate and interact within the symbiotic relationship between plants and nodules, including nitrogen (N)/carbon (C) metabolisms, oxygen flow through nodules, oxidative stress, and phosphorous (P) levels. These processes, which influence the regulation of N₂ fixation and are finely tuned on a whole-plant basis, are extensively reviewed in this paper. The carbonic anhydrase (CA)-phosphoenolpyruvate carboxylase (PEPC)-malate dehydrogenase (MDH) is a key pathway inside nodules involved in this regulation, and malate seems to play a crucial role in many aspects of symbiotic N₂ fixation control. How legumes specifically sense N-status and how this stimulates all of the regulatory factors are key issues for understanding N₂ fixation regulation on a whole-plant basis. This must be thoroughly studied in the future since there is no unifying theory that explains all of the aspects involved in regulating N₂ fixation rates to date. Finally, high-throughput functional genomics and molecular tools (i.e., miRNAs) are currently very valuable for the identification of many regulatory elements that are good candidates for accurately dissecting the particular N₂ fixation control mechanisms associated with physiological responses to abiotic stresses. In combination with existing information, utilizing these abundant genetic molecular tools will enable us to identify the specific mechanisms underlying the regulation of N₂ fixation. Full article

(This article belongs to the Special Issue Nitrogen-Fixing Plants )

► Show Figures

Figure 1

11 pages, 692 KiB

Open AccessEditor’s ChoiceReview

A Review of Plant Vacuoles: Formation, Located Proteins, and Functions

by Xiaona Tan, Kaixia Li, Zheng Wang, Keming Zhu, Xiaoli Tan and Jun Cao

Plants 2019, 8(9), 327; https://doi.org/10.3390/plants8090327 - 5 Sep 2019

Cited by 55 | Viewed by 10185

Abstract

Vacuoles, cellular membrane-bound organelles, are the largest compartments of cells, occupying up to 90% of the volume of plant cells. Vacuoles are formed by the biosynthetic and endocytotic pathways. In plants, the vacuole is crucial for growth and development and has a variety [...] Read more.

Vacuoles, cellular membrane-bound organelles, are the largest compartments of cells, occupying up to 90% of the volume of plant cells. Vacuoles are formed by the biosynthetic and endocytotic pathways. In plants, the vacuole is crucial for growth and development and has a variety of functions, including storage and transport, intracellular environmental stability, and response to injury. Depending on the cell type and growth conditions, the size of vacuoles is highly dynamic. Different types of cell vacuoles store different substances, such as alkaloids, protein enzymes, inorganic salts, sugars, etc., and play important roles in multiple signaling pathways. Here, we summarize vacuole formation, types, vacuole-located proteins, and functions. Full article

(This article belongs to the Section Plant Physiology and Metabolism)

► Show Figures

Figure 1

18 pages, 622 KiB

Open AccessEditor’s ChoiceArticle

SNP and Haplotype-Based Genomic Selection of Quantitative Traits in Eucalyptus globulus

by Paulina Ballesta, Carlos Maldonado, Paulino Pérez-Rodríguez and Freddy Mora

Plants 2019, 8(9), 331; https://doi.org/10.3390/plants8090331 - 5 Sep 2019

Cited by 31 | Viewed by 5535

Abstract

Eucalyptus globulus (Labill.) is one of the most important cultivated eucalypts in temperate and subtropical regions and has been successfully subjected to intensive breeding. In this study, Bayesian genomic models that include the effects of haplotype and single nucleotide polymorphisms (SNP) were assessed [...] Read more.

Eucalyptus globulus (Labill.) is one of the most important cultivated eucalypts in temperate and subtropical regions and has been successfully subjected to intensive breeding. In this study, Bayesian genomic models that include the effects of haplotype and single nucleotide polymorphisms (SNP) were assessed to predict quantitative traits related to wood quality and tree growth in a 6-year-old breeding population. To this end, the following markers were considered: (a) ~14 K SNP markers (SNP), (b) ~3 K haplotypes (HAP), and (c) haplotypes and SNPs that were not assigned to a haplotype (HAP-SNP). Predictive ability values (PA) were dependent on the genomic prediction models and markers. On average, Bayesian ridge regression (BRR) and Bayes C had the highest PA for the majority of traits. Notably, genomic models that included the haplotype effect (either HAP or HAP-SNP) significantly increased the PA of low-heritability traits. For instance, BRR based on HAP had the highest PA (0.58) for stem straightness. Consistently, the heritability estimates from genomic models were higher than the pedigree-based estimates for these traits. The results provide additional perspectives for the implementation of genomic selection in Eucalyptus breeding programs, which could be especially beneficial for improving traits with low heritability. Full article

(This article belongs to the Special Issue Genomics for Plant Breeding)

► Show Figures

Figure 1

15 pages, 2158 KiB

Open AccessEditor’s ChoiceArticle

Early Season Drought Largely Reduces Grain Yield in Wheat Cultivars with Smaller Root Systems

by Victoria Figueroa-Bustos, Jairo A. Palta, Yinglong Chen and Kadambot H.M. Siddique

Plants 2019, 8(9), 305; https://doi.org/10.3390/plants8090305 - 27 Aug 2019

Cited by 27 | Viewed by 3716

Abstract

In the Australian grainbelt, early winter rainfall has declined during the last 30 years, and farmers sow their crops dry, increasing the risk of early season drought. This study aimed to examine whether differences in the root systems were associated with tolerance to [...] Read more.

In the Australian grainbelt, early winter rainfall has declined during the last 30 years, and farmers sow their crops dry, increasing the risk of early season drought. This study aimed to examine whether differences in the root systems were associated with tolerance to early season drought. Three wheat cultivars with different root systems were grown in 1 m columns in a glasshouse. Immediately after sowing in dry soil, 440 mL water (equivalent to 25 mm rainfall) was supplied to each column, and no water was added to induce the early-season drought for the next 30 days. Shoot and root traits were measured at the end of the early season drought, anthesis and at maturity, respectively. The restricted water supply reduced Ψ_leaf, stomatal conductance, leaf photosynthetic rate, shoot and root biomass. Early season drought delayed phenology in all cultivars, but there was recovery of root and shoot biomass at anthesis in all three cultivars. Leaf area and shoot biomass at anthesis in Bahatans-87 (large root system) recovered better than Tincurrin (small root system). At maturity, early season drought reduced grain yield more in Tincurrin than Bahatans-87. The slow phenology of Bahatans-87 allowed greater recovery after the drought in leaf area and shoot biomass, which may explain the smaller reduction in grain yield after early season drought. Full article

(This article belongs to the Special Issue Root System Structure and Function: A Themed Issue in Honor of Professor Yoav Waisel)

► Show Figures

Figure 1

22 pages, 2297 KiB

Open AccessEditor’s ChoiceArticle

GWAS for Starch-Related Parameters in Japonica Rice (Oryza sativa L.)

by Chiara Biselli, Andrea Volante, Francesca Desiderio, Alessandro Tondelli, Alberto Gianinetti, Franca Finocchiaro, Federica Taddei, Laura Gazza, Daniela Sgrulletta, Luigi Cattivelli and Giampiero Valè

Plants 2019, 8(8), 292; https://doi.org/10.3390/plants8080292 - 19 Aug 2019

Cited by 29 | Viewed by 6414

Abstract

Rice quality is mainly related to the following two starch components, apparent amylose content (AAC) and resistant starch (RS). The former affects grain cooking properties, while RS acts as a prebiotic. In the present study, a Genome Wide Association Scan (GWAS) was performed [...] Read more.

Rice quality is mainly related to the following two starch components, apparent amylose content (AAC) and resistant starch (RS). The former affects grain cooking properties, while RS acts as a prebiotic. In the present study, a Genome Wide Association Scan (GWAS) was performed using 115 rice japonica accessions, including tropical and temperate genotypes, with the purpose of expanding the knowledge of the genetic bases affecting RS and AAC. High phenotypic variation was recorded for the two traits, which positively correlated. Moreover, both the parameters correlated with seed length (positive correlation) and seed width (negative correlation). A correlational selection according to human preferences has been hypothesized for the two starch traits and grain size. In addition, human selection has been proposed as the causal agent even for the different phenotypes related to starch and grain size showed by the tropical and temperate japonica accessions utilized in this study. The present GWAS led to the identification of 11 associations for RS on seven chromosomes and five associations for AAC on chromosome 6. Candidate genes and co-positional relationships with quantitative trait loci (QTLs) previously identified as affecting RS and AAC were identified for 6 associations. The candidate genes and the new RS- and/or AAC-associated regions detected provide valuable sources for future functional characterizations and for breeding programs aimed at improving rice grain quality. Full article

(This article belongs to the Special Issue Cereal Breeding: Improving Seed Vigour Traits and Grain Quality)

► Show Figures

Figure 1

12 pages, 1399 KiB

Open AccessEditor’s ChoiceArticle

Transient Heat Waves May Affect the Photosynthetic Capacity of Susceptible Wheat Genotypes Due to Insufficient Photosystem I Photoprotection

by Erik Chovancek, Marek Zivcak, Lenka Botyanszka, Pavol Hauptvogel, Xinghong Yang, Svetlana Misheva, Sajad Hussain and Marian Brestic

Plants 2019, 8(8), 282; https://doi.org/10.3390/plants8080282 - 12 Aug 2019

Cited by 49 | Viewed by 4487

Abstract

We assessed the photosynthetic responses of eight wheat varieties in conditions of a simulated heat wave in a transparent plastic tunnel for one week. We found that high temperatures (up to 38 °C at midday and above 20 °C at night) had a [...] Read more.

We assessed the photosynthetic responses of eight wheat varieties in conditions of a simulated heat wave in a transparent plastic tunnel for one week. We found that high temperatures (up to 38 °C at midday and above 20 °C at night) had a negative effect on the photosynthetic functions of the plants and provided differentiation of genotypes through sensitivity to heat. Measurements of gas exchange showed that the simulated heat wave led to a 40% decrease in photosynthetic activity on average in comparison to the control, with an unequal recovery of individual genotypes after a release from stress. Our results indicate that the ability to recover after heat stress was associated with an efficient regulation of linear electron transport and the prevention of over-reduction in the acceptor side of photosystem I. Full article

(This article belongs to the Special Issue Molecular Mechanisms and Genetics of Plant Resistance to Abiotic Stress)

► Show Figures

Figure 1

12 pages, 2694 KiB

Open AccessEditor’s ChoiceArticle

Comparative and Phylogenetic Analyses of Ginger (Zingiber officinale) in the Family Zingiberaceae Based on the Complete Chloroplast Genome

by Yingxian Cui, Liping Nie, Wei Sun, Zhichao Xu, Yu Wang, Jing Yu, Jingyuan Song and Hui Yao

Plants 2019, 8(8), 283; https://doi.org/10.3390/plants8080283 - 12 Aug 2019

Cited by 51 | Viewed by 6816

Abstract

Zingiber officinale, commonly known as ginger, is an important plant of the family Zingiberaceae and is widely used as an herbal medicine and condiment. The lack of chloroplast genomic information hinders molecular research and phylogenetic analysis on ginger. We introduced the complete [...] Read more.

Zingiber officinale, commonly known as ginger, is an important plant of the family Zingiberaceae and is widely used as an herbal medicine and condiment. The lack of chloroplast genomic information hinders molecular research and phylogenetic analysis on ginger. We introduced the complete chloroplast genome of Z. officinale and identified its phylogenetic position in Zingiberaceae. The chloroplast genome of Z. officinale is 162,621 bp with a four-part circular structure and 36.1% GC content. All 113 unique genes were annotated. A total of 78 simple sequence repeats (SSRs) and 42 long repeat sequences, which are potential areas for species authentication, were found. Comparative analysis revealed some highly variable regions, including rps16-trnQ-UUG, atpH-atpI, trnT-UGU-trnL-UAA, ycf1, and psaC-ndhE. Moreover, the small single-copy (SSC) region was the most variable region in all four shared regions, indicating that it may be undergoing rapid nucleotide substitution in the family Zingiberaceae. Phylogenetic analysis based on all available chloroplasts of Zingiberales in the National Center for Biotechnology Information indicated that Zingiber is a sister branch to Kaempferia species. The availability of the Z. officinale chloroplast genome provided invaluable data for species-level authentication and phylogenetic analysis and can thus benefit further investigations on species in the family Zingiberaceae. Full article

(This article belongs to the Special Issue Plant Bioinformatics)

► Show Figures

Figure 1

13 pages, 705 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Growth Rate and Nutrient Content of Five Microalgae Species Cultivated in Greenhouses

by Maria N. Metsoviti, George Papapolymerou, Ioannis T. Karapanagiotidis and Nikolaos Katsoulas

Plants 2019, 8(8), 279; https://doi.org/10.3390/plants8080279 - 10 Aug 2019

Cited by 55 | Viewed by 5573

Abstract

The effect of different environmental conditions on the growth rate, biomass production, nutrient composition, and phenolic content of the microalgae species Chlorella vulgaris, Botryococcus braunii, Chlamydomonas reinhardtii, Euglena gracilis, and Nannochloropsis oculata was investigated. The experiments were conducted in [...] Read more.

The effect of different environmental conditions on the growth rate, biomass production, nutrient composition, and phenolic content of the microalgae species Chlorella vulgaris, Botryococcus braunii, Chlamydomonas reinhardtii, Euglena gracilis, and Nannochloropsis oculata was investigated. The experiments were conducted in open bioreactors in a greenhouse in three different periods (during October, March, and June), and in a controlled environment in a closed plant growth chamber. It was found that the growth rate and production of C. vulgaris and B. braunii was higher during March, C. reinhardtii and N. oculata grew better in June, and the growth of E. gracilis was similar in March and June. The lipid content of the biomass of all five species increased with increasing light intensity and temperature, while the nitrogen free extractable (NFE) content decreased and the protein, fiber, moisture, and ash content remained relatively unaffected. The phenolic content varied from species to species with E. gracilis having the highest and N. oculata the lowest content among the species studied. The results can be taken into account when cultivating the different microalgae studied in full scale applications, such as in open raceway bioreactors, where conditions could be adjusted to obtain the most favorable growth conditions, depending on the particular species cultivated. Full article

► Show Figures

Figure 1

14 pages, 4401 KiB

Open AccessEditor’s ChoiceArticle

Antioxidant, Antidiabetic, and Anticholinesterase Activities and Phytochemical Profile of Azorella glabra Wedd

by Immacolata Faraone, Dilip K. Rai, Daniela Russo, Lucia Chiummiento, Eloy Fernandez, Alka Choudhary and Luigi Milella

Plants 2019, 8(8), 265; https://doi.org/10.3390/plants8080265 - 3 Aug 2019

Cited by 29 | Viewed by 5068

Abstract

Oxidative stress is involved in different diseases, such as diabetes and neurodegenerative diseases. The genus Azorella includes about 70 species of flowering plant species; most of them are commonly used as food and in particular as a tea infusion in the Andean region [...] Read more.

Oxidative stress is involved in different diseases, such as diabetes and neurodegenerative diseases. The genus Azorella includes about 70 species of flowering plant species; most of them are commonly used as food and in particular as a tea infusion in the Andean region of South America in folk medicine to treat various chronic diseases. Azorella glabra Wedd. aerial parts were firstly analyzed for their in vitro antioxidant activity using different complementary assays. In particular, radical scavenging activity was tested against biological neutral radical DPPH; ferric reducing power and lipid peroxidation inhibitory capacity (FRAP and Beta-Carotene Bleaching tests) were also determined. The Relative Antioxidant Capacity Index (RACI) was used to compare data obtained by different assays. Then, the inhibitory ability of samples was investigated against α-amylase and α-glucosidase enzymes involved in diabetes and against acetylcholinesterase and butyrylcholinesterase enzymes considered as strategy for the treatment of Parkinson’s or Alzheimer’s diseases. Moreover, the phytochemical profile of the sample showing the highest RACI (1.35) and interesting enzymatic activities (IC₅₀ of 163.54 ± 9.72 and 215.29 ± 17.10 μg/mL in α-glucosidase and acetylcholinesterase inhibition, respectively) was subjected to characterization and quantification of its phenolic composition using LC-MS/MS analysis. In fact, the ethyl acetate fraction derived from ethanol extract by liquid/liquid extraction showed 29 compounds, most of them are cinnamic acid derivatives, flavonoid derivatives, and a terpene. To the best of our knowledge, this is the first report about the evaluation of significant biological activities and phytochemical profile of A. glabra, an important source of health-promoting phytochemicals. Full article

(This article belongs to the Special Issue Medicinal Plants)

► Show Figures

Graphical abstract

17 pages, 1666 KiB

Open AccessEditor’s ChoiceReview

Biology and Function of miR159 in Plants

by Anthony A. Millar, Allan Lohe and Gigi Wong

Plants 2019, 8(8), 255; https://doi.org/10.3390/plants8080255 - 30 Jul 2019

Cited by 94 | Viewed by 6812

Abstract

MicroR159 (miR159) is ancient, being present in the majority of land plants where it targets a class of regulatory genes called GAMYB or GAMYB-like via highly conserved miR159-binding sites. These GAMYB genes encode R2R3 MYB domain transcription factors that transduce the gibberellin (GA) [...] Read more.

MicroR159 (miR159) is ancient, being present in the majority of land plants where it targets a class of regulatory genes called GAMYB or GAMYB-like via highly conserved miR159-binding sites. These GAMYB genes encode R2R3 MYB domain transcription factors that transduce the gibberellin (GA) signal in the seed aleurone and the anther tapetum. Here, GAMYB plays a conserved role in promoting the programmed cell death of these tissues, where miR159 function appears weak. By contrast, GAMYB is not involved in GA-signaling in vegetative tissues, but rather its expression is deleterious, leading to the inhibition of growth and development. Here, the major function of miR159 is to mediate strong silencing of GAMYB to enable normal growth. Highlighting this requirement of strong silencing are conserved RNA secondary structures associated with the miR159-binding site in GAMYB mRNA that promotes miR159-mediated repression. Although the miR159-GAMYB pathway in vegetative tissues has been implicated in a number of different functions, presently no conserved role for this pathway has emerged. We will review the current knowledge of the different proposed functions of miR159, and how this ancient pathway has been used as a model to help form our understanding of miRNA biology in plants. Full article

(This article belongs to the Special Issue The Role of MicroRNAs in Plants)

► Show Figures

Figure 1

20 pages, 2692 KiB

Open AccessEditor’s ChoiceArticle

Foliar Application of Zinc Oxide Nanoparticles and Zinc Sulfate Boosts the Content of Bioactive Compounds in Habanero Peppers

by Josué I. García-López, Guillermo Niño-Medina, Emilio Olivares-Sáenz, Ricardo H. Lira-Saldivar, Enrique Díaz Barriga-Castro, Rigoberto Vázquez-Alvarado, Pablo A. Rodríguez-Salinas and Francisco Zavala-García

Plants 2019, 8(8), 254; https://doi.org/10.3390/plants8080254 - 30 Jul 2019

Cited by 135 | Viewed by 9079

Abstract

The physiological responses of habanero pepper plants (Capsicum chinense Jacq.) to foliar applications of zinc sulphate and zinc nano-fertilizer were evaluated in greenhouse trials. The effect of the supplement on fruit quality of habanero pepper was particularly observed. Habanero pepper plants were [...] Read more.

The physiological responses of habanero pepper plants (Capsicum chinense Jacq.) to foliar applications of zinc sulphate and zinc nano-fertilizer were evaluated in greenhouse trials. The effect of the supplement on fruit quality of habanero pepper was particularly observed. Habanero pepper plants were grown to maturity, and during the main stages of phenological development, they were treated with foliar applications of Zn at concentrations of 1000 and 2000 mg L⁻¹ in the form of zinc sulfate (ZnSO₄) and zinc oxide nanoparticles (ZnO NPs). Additional Zn was not supplied to the control treatment plants. ZnO NPs at a concentration of 1000 mg L⁻¹ positively affected plant height, stem diameter, and chlorophyll content, and increased fruit yield and biomass accumulation compared to control and ZnSO₄ treatments. ZnO NPs at 2000 mg L⁻¹ negatively affected plant growth but significantly increased fruit quality, capsaicin content by 19.3%, dihydrocapsaicin by 10.9%, and Scoville Heat Units by 16.4%. In addition, at 2000 ZnO NPs mg L⁻¹ also increased content of total phenols and total flavonoids (soluble + bound) in fruits (14.50% and 26.9%, respectively), which resulted in higher antioxidant capacity in ABTS (2,2′azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), DPPH (2,2-diphenyl-1-picrylhydrazyl), and FRAP (ferric reducing antioxidant power) (15.4%, 31.8%, and 20.5%, respectively). These results indicate that application of ZnO NPs could be employed in habanero pepper production to improve yield, quality, and nutraceutical properties of fruits. Full article

► Show Figures

Figure 1

14 pages, 1669 KiB

Open AccessEditor’s ChoiceReview

The Diverse Roles of Auxin in Regulating Leaf Development

by Yuanyuan Xiong and Yuling Jiao

Plants 2019, 8(7), 243; https://doi.org/10.3390/plants8070243 - 23 Jul 2019

Cited by 55 | Viewed by 10005

Abstract

Leaves, the primary plant organs that function in photosynthesis and respiration, have highly organized, flat structures that vary within and among species. In recent years, it has become evident that auxin plays central roles in leaf development, including leaf initiation, blade formation, and [...] Read more.

Leaves, the primary plant organs that function in photosynthesis and respiration, have highly organized, flat structures that vary within and among species. In recent years, it has become evident that auxin plays central roles in leaf development, including leaf initiation, blade formation, and compound leaf patterning. In this review, we discuss how auxin maxima form to define leaf primordium formation. We summarize recent progress in understanding of how spatial auxin signaling promotes leaf blade formation. Finally, we discuss how spatial auxin transport and signaling regulate the patterning of compound leaves and leaf serration. Full article

(This article belongs to the Special Issue From Genes to Shape and Function: Leaf Morphogenesis at Play)

► Show Figures

Figure 1

24 pages, 3660 KiB

Open AccessEditor’s ChoiceReview

What Makes Adventitious Roots?

by Mathieu Gonin, Véronique Bergougnoux, Thu D. Nguyen, Pascal Gantet and Antony Champion

Plants 2019, 8(7), 240; https://doi.org/10.3390/plants8070240 - 22 Jul 2019

Cited by 75 | Viewed by 28506

Abstract

The spermatophyte root system is composed of a primary root that develops from an embryonically formed root meristem, and of different post-embryonic root types: lateral and adventitious roots. Adventitious roots, arising from the stem of the plants, are the main component of the [...] Read more.

The spermatophyte root system is composed of a primary root that develops from an embryonically formed root meristem, and of different post-embryonic root types: lateral and adventitious roots. Adventitious roots, arising from the stem of the plants, are the main component of the mature root system of many plants. Their development can also be induced in response to adverse environmental conditions or stresses. Here, in this review, we report on the morphological and functional diversity of adventitious roots and their origin. The hormonal and molecular regulation of the constitutive and inducible adventitious root initiation and development is discussed. Recent data confirmed the crucial role of the auxin/cytokinin balance in adventitious rooting. Nevertheless, other hormones must be considered. At the genetic level, adventitious root formation integrates the transduction of external signals, as well as a core auxin-regulated developmental pathway that is shared with lateral root formation. The knowledge acquired from adventitious root development opens new perspectives to improve micropropagation by cutting in recalcitrant species, root system architecture of crops such as cereals, and to understand how plants adapted during evolution to the terrestrial environment by producing different post-embryonic root types. Full article

(This article belongs to the Special Issue Root System Structure and Function: A Themed Issue in Honor of Professor Yoav Waisel)

► Show Figures

Figure 1

10 pages, 504 KiB

Open AccessEditor’s ChoiceReview

WRINKLED1, a “Master Regulator” in Transcriptional Control of Plant Oil Biosynthesis

by Que Kong, Ling Yuan and Wei Ma

Plants 2019, 8(7), 238; https://doi.org/10.3390/plants8070238 - 22 Jul 2019

Cited by 44 | Viewed by 6610

Abstract

A majority of plant species generate and accumulate triacylglycerol (TAG) in their seeds, which is the main resource of carbon and energy supporting the process of seedling development. Plant seed oils have broad ranges of uses, being not only important for human diets [...] Read more.

A majority of plant species generate and accumulate triacylglycerol (TAG) in their seeds, which is the main resource of carbon and energy supporting the process of seedling development. Plant seed oils have broad ranges of uses, being not only important for human diets but also renewable feedstock of industrial applications. The WRINKLED1 (WRI1) transcription factor is vital for the transcriptional control of plant oil biosynthetic pathways. Since the identification of the Arabidopsis WRI1 gene (AtWRI1) fifteen years ago, tremendous progress has been made in understanding the functions of WRI1 at multiple levels, ranging from the identification of AtWRI1 target genes to location of the AtWRI1 binding motif, and from discovery of intrinsic structural disorder in WRI1 to fine-tuning of WRI1 modulation by post-translational modifications and protein-protein interactions. The expanding knowledge on the functional understanding of the WRI1 regulatory mechanism not only provides a clearer picture of transcriptional regulation of plant oil biosynthetic pathway, but also helps generate new strategies to better utilize WRI1 for developing novel oil crops. Full article

(This article belongs to the Special Issue Lipid Metabolism in Plants)

► Show Figures

Figure 1

23 pages, 1988 KiB

Open AccessEditor’s ChoiceArticle

Variations of Secondary Metabolites among Natural Populations of Sub-Antarctic Ranunculus Species Suggest Functional Redundancy and Versatility

by Bastien Labarrere, Andreas Prinzing, Thomas Dorey, Emeline Chesneau and Françoise Hennion

Plants 2019, 8(7), 234; https://doi.org/10.3390/plants8070234 - 19 Jul 2019

Cited by 22 | Viewed by 5420

Abstract

Plants produce a high diversity of metabolites which help them sustain environmental stresses and are involved in local adaptation. However, shaped by both the genome and the environment, the patterns of variation of the metabolome in nature are difficult to decipher. Few studies [...] Read more.

Plants produce a high diversity of metabolites which help them sustain environmental stresses and are involved in local adaptation. However, shaped by both the genome and the environment, the patterns of variation of the metabolome in nature are difficult to decipher. Few studies have explored the relative parts of geographical region versus environment or phenotype in metabolomic variability within species and none have discussed a possible effect of the region on the correlations between metabolites and environments or phenotypes. In three sub-Antarctic Ranunculus species, we examined the role of region in metabolite differences and in the relationship between individual compounds and environmental conditions or phenotypic traits. Populations of three Ranunculus species were sampled across similar environmental gradients in two distinct geographical regions in îles Kerguelen. Two metabolite classes were studied, amines (quantified by high-performance liquid chromatography and fluorescence spectrophotometry) and flavonols (quantified by ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry). Depending on regions, the same environment or the same trait may be related to different metabolites, suggesting metabolite redundancy within species. In several cases, a given metabolite showed different or even opposite relations with the same environmental condition or the same trait across the two regions, suggesting metabolite versatility within species. Our results suggest that metabolites may be functionally redundant and versatile within species, both in their response to environments and in their relation with the phenotype. These findings open new perspectives for understanding evolutionary responses of plants to environmental changes. Full article

(This article belongs to the Special Issue Plant Polyamines)

► Show Figures

Figure 1

18 pages, 2190 KiB

Open AccessEditor’s ChoiceArticle

Allelopathic and Autotoxic Effects of Medicago sativa—Derived Allelochemicals

by Bimal Kumar Ghimire, Balkrishna Ghimire, Chang Yeon Yu and Ill-Min Chung

Plants 2019, 8(7), 233; https://doi.org/10.3390/plants8070233 - 18 Jul 2019

Cited by 53 | Viewed by 6506

Abstract

In this study, the allelopathic properties of Medicago sativa on different weeds were investigated under in vitro conditions. The compounds involved in the autotoxicity of M. sativa were analyzed using high-performance liquid chromatography. The extracts of all concentrations inhibited the growth of the [...] Read more.

In this study, the allelopathic properties of Medicago sativa on different weeds were investigated under in vitro conditions. The compounds involved in the autotoxicity of M. sativa were analyzed using high-performance liquid chromatography. The extracts of all concentrations inhibited the growth of the calluses of Digitaria ciliaris, Chenopodium album, Amaranthus lividus, Portulaca oleracea, and Commelina communis. Six allelopathic compounds in alfalfa were identified and quantified, and the most predominant phenolic compounds were salicylic acid and p-hydroxybenzoic acid. Various concentrations (10⁻², 10⁻³, and 10⁻⁵ M) of all the tested phenolic compounds exerted inhibitory effects on callus fresh weight. Rutin, salicylic acid, scopoletin, and quercetin significantly inhibited alfalfa seed germination. Of the seven identified saponins, medicagenic acid saponins exhibited the highest autotoxic effect and significantly lowered seed germination rate. Principal component analysis showed that the phenolic compounds and saponin composition significantly contributed to the different variables. The highly phytotoxic properties of the alfalfa-derived phenolic compounds and saponins indicate that these phytochemicals can be a potential source of bioherbicides. Full article

► Show Figures

Figure 1

20 pages, 1147 KiB

Open AccessEditor’s ChoiceReview

Drought Stress Effects and Olive Tree Acclimation under a Changing Climate

by Cátia Brito, Lia-Tânia Dinis, José Moutinho-Pereira and Carlos M. Correia

Plants 2019, 8(7), 232; https://doi.org/10.3390/plants8070232 - 17 Jul 2019

Cited by 123 | Viewed by 11340

Abstract

Increasing consciousness regarding the nutritional value of olive oil has enhanced the demand for this product and, consequently, the expansion of olive tree cultivation. Although it is considered a highly resilient and tolerant crop to several abiotic stresses, olive growing areas are usually [...] Read more.

Increasing consciousness regarding the nutritional value of olive oil has enhanced the demand for this product and, consequently, the expansion of olive tree cultivation. Although it is considered a highly resilient and tolerant crop to several abiotic stresses, olive growing areas are usually affected by adverse environmental factors, namely, water scarcity, heat and high irradiance, and are especially vulnerable to climate change. In this context, it is imperative to improve agronomic strategies to offset the loss of productivity and possible changes in fruit and oil quality. To develop more efficient and precise measures, it is important to look for new insights concerning response mechanisms to drought stress. In this review, we provided an overview of the global status of olive tree ecology and relevance, as well the influence of environmental abiotic stresses in olive cultivation. Finally, we explored and analysed the deleterious effects caused by drought (e.g., water status and photosynthetic performance impairment, oxidative stress and imbalance in plant nutrition), the most critical stressor to agricultural crops in the Mediterranean region, and the main olive tree responses to withstand this stressor. Full article

(This article belongs to the Section Plant Physiology and Metabolism)

► Show Figures

Figure 1

18 pages, 4432 KiB

Open AccessEditor’s ChoiceArticle

Effect of Selenium on Alleviating Oxidative Stress Caused by a Water Deficit in Cucumber Roots

by Weronika Jóźwiak and Barbara Politycka

Plants 2019, 8(7), 217; https://doi.org/10.3390/plants8070217 - 11 Jul 2019

Cited by 73 | Viewed by 5197

Abstract

The aim of the study was to evaluate the antioxidant activity of selenium in the roots of Cucumis sativus L. seedlings pre-treated with selenium (Se) in the form of sodium selenite at concentrations of 1, 5, and 10 µM, and then subjected to [...] Read more.

The aim of the study was to evaluate the antioxidant activity of selenium in the roots of Cucumis sativus L. seedlings pre-treated with selenium (Se) in the form of sodium selenite at concentrations of 1, 5, and 10 µM, and then subjected to a water deficit (WD). It has been hypothesized that Se, in low concentrations, alleviates an oxidative stress caused by a WD in the cucumber roots. A WD was introduced by the surface dehydration of roots. The aim of the research was to compare the changes accompanying oxidative stress in plants growing in the presence of Se and in its absence. The study concerns the generation of reactive oxygen species (ROS)—superoxide anions (O₂^•−), hydrogen peroxide (H₂O₂), and hydroxyl radicals (^•OH)—as well the activities of the antioxidant enzymes lowering the ROS level—ascorbate peroxidase (APX), peroxidase (POX), catalase (CAT), and superoxide dismutase (SOD). A WD caused oxidative stress, i.e., the enhanced generation of ROS. Selenium at the concentrations of 1 and 5 μM increased the tolerance of cucumber seedlings to oxidative stress caused by a WD by increasing the activities of the antioxidant enzymes, and it also limited the damage of plasma membranes as a result of the inhibition of lipid peroxidation. Full article

(This article belongs to the Special Issue Selenium Metabolism and Accumulation in Plants)

► Show Figures

Figure 1

13 pages, 1343 KiB

Open AccessEditor’s ChoiceReview

On the Ecology of Selenium Accumulation in Plants

by Elizabeth A. H. Pilon-Smits

Plants 2019, 8(7), 197; https://doi.org/10.3390/plants8070197 - 30 Jun 2019

Cited by 59 | Viewed by 7448

Abstract

Plants accumulate and tolerate Se to varying degrees, up to 15,000 mg Se/kg dry weight for Se hyperaccumulators. Plant Se accumulation may exert positive or negative effects on other species in the community. The movement of plant Se into ecological partners may benefit [...] Read more.

Plants accumulate and tolerate Se to varying degrees, up to 15,000 mg Se/kg dry weight for Se hyperaccumulators. Plant Se accumulation may exert positive or negative effects on other species in the community. The movement of plant Se into ecological partners may benefit them at low concentrations, but cause toxicity at high concentrations. Thus, Se accumulation can protect plants against Se-sensitive herbivores and pathogens (elemental defense) and reduce surrounding vegetation cover via high-Se litter deposition (elemental allelopathy). While hyperaccumulators negatively impact Se-sensitive ecological partners, they offer a niche for Se-tolerant partners, including beneficial microbial and pollinator symbionts as well as detrimental herbivores, pathogens, and competing plant species. These ecological effects of plant Se accumulation may facilitate the evolution of Se resistance in symbionts. Conversely, Se hyperaccumulation may evolve driven by increasing Se resistance in herbivores, pathogens, or plant neighbors; Se resistance also evolves in mutualist symbionts, minimizing the plant’s ecological cost. Interesting topics to address in future research are whether the ecological impacts of plant Se accumulation may affect species composition across trophic levels (favoring Se resistant taxa), and to what extent Se hyperaccumulators form a portal for Se into the local food chain and are important for Se cycling in the local ecosystem. Full article

(This article belongs to the Special Issue Selenium Metabolism and Accumulation in Plants)

► Show Figures

Graphical abstract

17 pages, 2014 KiB

Open AccessEditor’s ChoiceReview

Melatonin Mediated Regulation of Drought Stress: Physiological and Molecular Aspects

by Anket Sharma and Bingsong Zheng

Plants 2019, 8(7), 190; https://doi.org/10.3390/plants8070190 - 26 Jun 2019

Cited by 146 | Viewed by 9757

Abstract

Drought stress adversely effects physiological and biochemical processes of plants, leading to a reduction in plant productivity. Plants try to protect themselves via activation of their internal defense system, but severe drought causes dysfunction of this defense system. The imbalance between generation and [...] Read more.

Drought stress adversely effects physiological and biochemical processes of plants, leading to a reduction in plant productivity. Plants try to protect themselves via activation of their internal defense system, but severe drought causes dysfunction of this defense system. The imbalance between generation and scavenging of reactive oxygen species (ROS) leads to oxidative stress. Melatonin, a multifunctional molecule, has the potential to protect plants from the adverse effects of drought stress by enhancing the ROS scavenging efficiency. It helps in protection of photosynthetic apparatus and reduction of drought induced oxidative stress. Melatonin regulates plant processes at a molecular level, which results in providing better resistance against drought stress. In this review, the authors have discussed various physiological and molecular aspects regulated by melatonin in plants under drought conditions, along with their underlying mechanisms. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

► Show Figures

Graphical abstract

13 pages, 763 KiB

Open AccessEditor’s ChoiceReview

Reactive Oxygen Species as Potential Drivers of the Seed Aging Process

by Katarzyna Kurek, Beata Plitta-Michalak and Ewelina Ratajczak

Plants 2019, 8(6), 174; https://doi.org/10.3390/plants8060174 - 14 Jun 2019

Cited by 121 | Viewed by 8024

Abstract

Seeds are an important life cycle stage because they guarantee plant survival in unfavorable environmental conditions and the transfer of genetic information from parents to offspring. However, similar to every organ, seeds undergo aging processes that limit their viability and ultimately cause the [...] Read more.

Seeds are an important life cycle stage because they guarantee plant survival in unfavorable environmental conditions and the transfer of genetic information from parents to offspring. However, similar to every organ, seeds undergo aging processes that limit their viability and ultimately cause the loss of their basic property, i.e., the ability to germinate. Seed aging is a vital economic and scientific issue that is related to seed resistance to an array of factors, both internal (genetic, structural, and physiological) and external (mainly storage conditions: temperature and humidity). Reactive oxygen species (ROS) are believed to initiate seed aging via the degradation of cell membrane phospholipids and the structural and functional deterioration of proteins and genetic material. Researchers investigating seed aging claim that the effective protection of genetic resources requires an understanding of the reasons for senescence of seeds with variable sensitivity to drying and long-term storage. Genomic integrity considerably affects seed viability and vigor. The deterioration of nucleic acids inhibits transcription and translation and exacerbates reductions in the activity of antioxidant system enzymes. All of these factors significantly limit seed viability. Full article

(This article belongs to the Special Issue Genetics of Seed Germination and Growth)

► Show Figures

Figure 1

15 pages, 2339 KiB

Open AccessEditor’s ChoiceArticle

Waterlogging Causes Early Modification in the Physiological Performance, Carotenoids, Chlorophylls, Proline, and Soluble Sugars of Cucumber Plants

by T. Casey Barickman, Catherine R. Simpson and Carl E. Sams

Plants 2019, 8(6), 160; https://doi.org/10.3390/plants8060160 - 8 Jun 2019

Cited by 98 | Viewed by 7449

Abstract

Waterlogging occurs because of poor soil drainage and/or excessive rainfall and is a serious abiotic stress affecting plant growth because of declining oxygen supplied to submerged tissues. Although cucumber (Cucumis sativus L.) is sensitive to waterlogging, its ability to generate adventitious roots [...] Read more.

Waterlogging occurs because of poor soil drainage and/or excessive rainfall and is a serious abiotic stress affecting plant growth because of declining oxygen supplied to submerged tissues. Although cucumber (Cucumis sativus L.) is sensitive to waterlogging, its ability to generate adventitious roots facilitates gas diffusion and increases plant survival when oxygen concentrations are low. To understand the physiological responses to waterlogging, a 10-day waterlogging experiment was conducted. The objective of this study was to measure the photosynthetic and key metabolites of cucumber plants under waterlogging conditions for 10 days. Plants were also harvested at the end of 10 days and analyzed for plant height (ht), leaf number and area, fresh mass (FM), dry mass (DM), chlorophyll (Chl), carotenoid (CAR), proline, and soluble sugars. Results indicated that cucumber plants subjected to the 10-day waterlogging stress conditions were stunted, had fewer leaves, and decreased leaf area, FM, and DM. There were differences in physiological performance, Chl, CAR, proline, and soluble sugars. Overall, waterlogging stress decreased net photosynthesis (A), having a negative effect on biomass accumulation. However, these decreases were also dependent on other factors, such as plant size, morphology, and water use efficiency (WUE) that played a role in the overall metabolism of the plant. Full article

(This article belongs to the Section Plant Physiology and Metabolism)

► Show Figures

Figure 1

13 pages, 1641 KiB

Open AccessEditor’s ChoiceReview

Herbicide Resistance Management: Recent Developments and Trends

by Hugh J. Beckie, Michael B. Ashworth and Ken C. Flower

Plants 2019, 8(6), 161; https://doi.org/10.3390/plants8060161 - 8 Jun 2019

Cited by 84 | Viewed by 9703

Abstract

This review covers recent developments and trends in herbicide-resistant (HR) weed management in agronomic field crops. In countries where input-intensive agriculture is practiced, these developments and trends over the past decade include renewed efforts by the agrichemical industry in herbicide discovery, cultivation of [...] Read more.

This review covers recent developments and trends in herbicide-resistant (HR) weed management in agronomic field crops. In countries where input-intensive agriculture is practiced, these developments and trends over the past decade include renewed efforts by the agrichemical industry in herbicide discovery, cultivation of crops with combined (stacked) HR traits, increasing reliance on preemergence vs. postemergence herbicides, breeding for weed-competitive crop cultivars, expansion of harvest weed seed control practices, and advances in site-specific or precision weed management. The unifying framework or strategy underlying these developments and trends is mitigation of viable weed seeds into the soil seed bank and maintaining low weed seed banks to minimize population proliferation, evolution of resistance to additional herbicidal sites of action, and spread. A key question going forward is: how much weed control is enough to consistently achieve the goal of low weed seed banks? The vision for future HR weed management programs must be sustained crop production and profitability with reduced herbicide (particularly glyphosate) dependency. Full article

(This article belongs to the Special Issue Herbicide Resistance in Plants)

► Show Figures

Figure 1

12 pages, 2166 KiB

Open AccessEditor’s ChoiceReview

Ascorbic Acid and Ozone: Novel Perspectives to Explain an Elusive Relationship

by Erika Bellini and Mario C. De Tullio

Plants 2019, 8(5), 122; https://doi.org/10.3390/plants8050122 - 9 May 2019

Cited by 44 | Viewed by 5048

Abstract

A huge amount of studies highlighted the importance of high ascorbic acid (AA) content in ozone tolerance, yet the relationship between them appears more complex than a simple direct correlation. Sometimes the connection is clear, for example, two Arabidopsis mutants defective in the [...] Read more.

A huge amount of studies highlighted the importance of high ascorbic acid (AA) content in ozone tolerance, yet the relationship between them appears more complex than a simple direct correlation. Sometimes the connection is clear, for example, two Arabidopsis mutants defective in the main AA biosynthetic pathway (vtc mutants) were identified by means of their ozone sensitivity. However, some low-AA containing mutants are relatively tolerant, suggesting that AA location/availability could be more relevant than total content. A clear distinction should also be made between ozone tolerance obtained when AA content is increased by experimental supplementation (exogenous AA), and the physiological role of plant-synthesized AA (endogenous AA), whose amount is apparently subjected to tight regulation. Recent findings about the role of AA in signal transduction and epigenetic regulation of gene expression open new routes to further research. Full article

(This article belongs to the Special Issue Ozone Tolerance Mechanisms)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Editor’s Choice Articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI