Biochemical Defenses of Plants

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Phytochemistry".

Deadline for manuscript submissions: 15 August 2024 | Viewed by 2870

Special Issue Editors


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Guest Editor
Department of Biology, Faculty of Science, York University, Toronto, ON M3J 1P3, Canada
Interests: plant metabolism; secondary metabolism; gene regulatory networks; bioengineering

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Guest Editor
School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong
Interests: plant secondary metabolism; flavonoid, stilbene, and lignin biosynthesis; metabolic engineering

Special Issue Information

Dear Colleagues,

Plants are often referred to as ‘nature’s chemists’ since they collectively biosynthesize hundreds of thousands of specialized metabolites. Plant-specialized metabolites have direct economic value as pharmaceuticals, food additives, and other industrial uses, yet they have a prominent role in defending plants, including major crop species, against important agricultural pests and pathogens. These include pathogenic bacteria, fungi, oomycetes, phytoplasma, viruses, viroids, other plant species, and macro- and microscopic animals such as insects and nematodes. Thus, understanding the biochemical defences of plants, including their biochemical diversity, biosynthesis, degradation, complex signalling, and regulatory networks, and their roles in mediating interactions with other organisms, will inform genetic engineering or breeding strategies to enhance their production to support sustainable agriculture and the supply of plant-derived small-molecule-type pharmaceuticals.

This Special Issue of Plants will highlight all novel aspects of the biochemical defences of plants at the genetic, molecular, biochemical, cellular, organismal, and ecological levels. Scientists from all over the world are invited to submit original research and review articles on topics related to the biochemical defences of plants.

Dr. Nik Kovinich
Prof. Dr. Philippe Jeandet
Dr. Clive Lo
Guest Editors

Manuscript Submission Information

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Keywords

  • defence mechanisms
  • biochemical defence
  • disease resistance
  • antimicrobial activity
  • biological activity
  • defence metabolites
  • specialized metabolites
  • secondary metabolites
  • phytoalexins
  • phytoanticipins
  • elicitors
  • pathogens
  • microorganisms
  • insects
  • nematodes

Published Papers (3 papers)

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Research

17 pages, 2877 KiB  
Article
Nitrogen and Silicon Contribute to Wheat Defense’s to Pyrenophora tritici-repentis, but in an Independent Manner
by Andrea Elizabeth Román Ramos, Carlos Eduardo Aucique-Perez, Daniel Debona and Leandro José Dallagnol
Plants 2024, 13(11), 1426; https://doi.org/10.3390/plants13111426 - 21 May 2024
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Abstract
Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction [...] Read more.
Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction effect on wheat resistance to tan spot remains elusive. Histocytological and biochemical defense responses against Ptr in wheat leaves treated with Si (+Si) at low (LN) and high N (HN) inputs were investigated. Soil amendment with Si reduced the tan spot severity in 18% due to the increase in the leaf Si concentration (around 30%), but it was affected by the N level used. The superoxide dismutase (SOD) activity was higher in +Si plants and inoculated with Ptr, leading to early and higher H2O2 and callose accumulation in wheat leaf. Interestedly, phenylalanine ammonia-lyase (PAL) activity was induced by the Si supplying, being negatively affected by the HN rate. Meanwhile, catalase (CAT), and peroxidase (POX) activities showed differential response patterns according to the Si and N rates used. Tan spot severity was reduced by both elements, but their interaction does not evidence synergic effects in this disease’s control. Wheat plants from −Si and HN and +Si and LN treatments recorded lower tan spot severity. Full article
(This article belongs to the Special Issue Biochemical Defenses of Plants)
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21 pages, 3073 KiB  
Article
Aphid Resistance Segregates Independently of Cardenolide and Glucosinolate Content in an Erysimum cheiranthoides (Wormseed Wallflower) F2 Population
by Mahdieh Mirzaei, Gordon C. Younkin, Adrian F. Powell, Martin L. Alani, Susan R. Strickler and Georg Jander
Plants 2024, 13(4), 466; https://doi.org/10.3390/plants13040466 - 6 Feb 2024
Cited by 1 | Viewed by 772
Abstract
Plants in the genus Erysimum produce both glucosinolates and cardenolides as a defense mechanism against herbivory. Two natural isolates of Erysimum cheiranthoides (wormseed wallflower) differed in their glucosinolate content, cardenolide content, and their resistance to Myzus persicae (green peach aphid), a broad generalist [...] Read more.
Plants in the genus Erysimum produce both glucosinolates and cardenolides as a defense mechanism against herbivory. Two natural isolates of Erysimum cheiranthoides (wormseed wallflower) differed in their glucosinolate content, cardenolide content, and their resistance to Myzus persicae (green peach aphid), a broad generalist herbivore. Both classes of defensive metabolites were produced constitutively and were not further induced by aphid feeding. To investigate the relative importance of glucosinolates and cardenolides in E. cheiranthoides defense, we generated an improved genome assembly, genetic map, and segregating F2 population. The genotypic and phenotypic analysis of the F2 plants identified quantitative trait loci, which affected glucosinolates and cardenolides, but not the aphid resistance. The abundance of most glucosinolates and cardenolides was positively correlated in the F2 population, indicating that similar processes regulate their biosynthesis and accumulation. Aphid reproduction was positively correlated with glucosinolate content. Although the overall cardenolide content had little effect on aphid growth and survival, there was a negative correlation between aphid reproduction and helveticoside abundance. However, this variation in defensive metabolites could not explain the differences in aphid growth on the two parental lines, suggesting that processes other than the abundance of glucosinolates and cardenolides have a predominant effect on aphid resistance in E. cheiranthoides. Full article
(This article belongs to the Special Issue Biochemical Defenses of Plants)
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13 pages, 1893 KiB  
Article
Nematocidal Potential of Phenolic Acids: A Phytochemical Seed-Coating Approach to Soybean Cyst Nematode Management
by Ping Yates, Juddy Janiol, Changbao Li and Bao-Hua Song
Plants 2024, 13(2), 319; https://doi.org/10.3390/plants13020319 - 21 Jan 2024
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Abstract
Soybeans, one of the most valuable crops worldwide, are annually decimated by the soybean cyst nematode (SCN), Heterodera glycines, resulting in massive losses in soybean yields and economic revenue. Conventional agricultural pesticides are generally effective in the short term; however, they pose [...] Read more.
Soybeans, one of the most valuable crops worldwide, are annually decimated by the soybean cyst nematode (SCN), Heterodera glycines, resulting in massive losses in soybean yields and economic revenue. Conventional agricultural pesticides are generally effective in the short term; however, they pose growing threats to human and environmental health; therefore, alternative SCN management strategies are urgently needed. Preliminary findings show that phenolic acids are significantly induced during SCN infection and exhibit effective nematocidal activities in vitro. However, it is unclear whether these effects occur in planta or elicit any negative effects on plant growth traits. Here, we employed a phytochemical-based seed coating application on soybean seeds using phenolic acid derivatives (4HBD; 2,3DHBA) at variable concentrations and examined SCN inhibition against two SCN types. Moreover, we also examined plant growth traits under non-infected or SCN infected conditions. Notably, 2,3DHBA significantly inhibited SCN abundance in Race 2-infected plants with increasingly higher chemical doses. Interestingly, neither compound negatively affected soybean growth traits in control or SCN-infected plants. Our findings suggest that a phytochemical-based approach could offer an effective, more environmentally friendly solution to facilitate current SCN management strategies and fast-track the development of biopesticides to sustainably manage devastating pests such as SCN. Full article
(This article belongs to the Special Issue Biochemical Defenses of Plants)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Timing is everything: Metabolic partitioning of suberin-destined carbon
Authors: JESSICA L. SINKA and MARK A. BERNARDS
Affiliation: Department of Biology, Western University, London, ON, N6A 5B7, Canada
Abstract: Suberin is a cell wall-associated biopolymer that possesses both poly(phenolic) and poly(aliphatic) elements assembled into chemically and spatially distinct domains. Domain-specific monomers are formed via a branched pathway between phenolic and aliphatic metabolisms. Transcript accumulation data (RNAseq), from the early stages of wound-induced suberization, revealed highly coordinated, temporal changes in regulation of the ‘branches’. Notably, phenolic-associated transcripts accumulated first which could indicate a preference toward phenolic production early on post-wounding. To better understand the dynamics of suberin monomer biosynthesis and assembly, we quantified the allocation of carbon between phenolic and aliphatic metabolisms in a wound-induced suberin model. To do so, [13C]-glucose was administered to wound-healing potato tuber discs at different times post-wounding and patterns of heavy carbon incorporation into primary metabolites assessed. During the early stages of wound healing, carbon from [13C]-glucose was rapidly incorporated into phenolic-destined metabolites and sucrose, while at later stages it was shared between phenolic- and aliphatic-destined metabolites. Labelled carbon was ultimately found in both the poly(phenolic) and poly(aliphatic) domains, regardless of when the [13C]-glucose was applied. Because suberin is an innate physical barrier that confers resistance to drought, pathogens, and desiccation during crop storage, understanding it’s temporal regulation can help inform strategies for crop enhancement through genetic engineering and/or marker-assisted breeding.

Title: Altered metabolism in knockdown lines of two HXXXD/BAHD acyltransferases in wound-healing potatoes
Authors: SAU KEI (LORENA) YEUNG1, INDIRA QUERALTA CASTILLO1, JESSICA L. SINKA1, EMILY DRENNAN1, GEORGE DEL GROSSO1, ISABEL MOLINA2, SANGEETA DHAUBHADEL1,3, MARK A. BERNARDS1
Affiliation: 1Department of Biology, Western University, London, ON, N6A 5B7, Canada, 2Department of Biology, Algoma University, Sault St. Marie, ON, P6A 2G4, Canada, 3London Research and Development Centre, Agriculture and Agri-Food Canada, 1391 Sandford St, London, Ontario, N5V 4T3, Canada
Abstract: Suberin is a phenolic-lipophilic biopolymer that functions as a physical barrier to protect plants from environmental stressors such as desiccation and pathogen infection. It is composed of two spatially distinct domains, the poly(phenolic) domain and the poly(aliphatic) domain. Using RNAseq data, we identified StFHT (Fatty ω-hydroxyacid/fatty alcohol Hydroxycinnamoyl Transferase) and two uncharacterized potato (Solanum tuberosum L.) HXXXD/BAHD acyltransferases, designated StHCT (HydroxyCinnamoyl Transferase) and StACT (ACyl Transferase), as highly expressed upon wounding. While StFHT has been previously characterized, StHCT and StACT have not. Despite being more closely related to hydroxycinnamoyl-quinate hydroxycinnamoyl transferases than StFHT, analysis from independently generated RNAi-silenced StFHT lines and StHCT lines revealed the same suberin phenotype of decreased alkyl ferulate ester production and reduced esterified ferulic acid in wound-induced potato tubers of both genotypes. StACT-RNAi knockdown lines, however, were indistinguishable from wild-type (WT). To assess the upstream effects of impaired ferulate ester production, metabolites were extracted from suberizing empty vector (WT control), StFHT-RNAi, and StHCT-RNAi microtubers over 8 days post wounding. Overall, StFHT knockdown lines accumulated alternative ferulate conjugates (esp. feruloyltyramine), while StHCT knockdown lines accumulated p-coumaroyl derivatives. These data support the function of STHCT in upstream hydroxycinnamic acid biosynthesis and the critical role of phenolic metabolism in suberin formation.

Title: Bioactive immunoadjuvant saponins from /Quillaja lancifolia/ act as antifungal and herbivore deterrents
Authors: Yendo, A.C.A.; Matsuura, H.N.; Colling, L.C.; De Costa, F.; Vargas, L.R.B.; Martinelli, J.A.; Graichen, F.; Vainstein, M.H.; Landell, M.F.; Fett-Neto, A.G.
Affiliation: Federal University of Rio Grande do Sul, Brazil
Abstract: Saponins from leaves of /Quillaja lancifolia/, a native species from southern Brazil, show immunoadjuvant activity in several experimental vaccine formulations. The accumulation of the immunoadjuvant saponin fraction QB-90 is induced by several stresses and stress signaling molecules in cultured leaf disks and seedlings, suggesting that these terpenes may be players in defense responses. An investigation of the potential inhibitory role of /Q. lancifolia /saponins on plant pathogenic fungi and two herbivore models was carried out. The results revealed that /Q. lancifolia /saponins had antifungal activity against several phytopathogenic fungi, including /Bipolaris micropus, Curvularia inaequalis /and /Fusarium incarnatum/. In addition, the same saponins acted as deterrents against the generalist insect and mollusk herbivores /Spodoptera frugiperda/ and /Helix aspersa/, respectively. Significant reductions in consumption of leaf area and weight (larvae) were recorded. Data support a role for /Q. lancifolia/ saponins in plant defense against fungi and herbivores, thereby having potential as natural control agent against plant pests or as molecular platforms for new molecule development.

Title: Phosphite containing nickel and potassium potentiates soybean defense against infection by Phakopsora pachyrhizi
Authors: Fabricio Rodrigues
Affiliation: Universidade Federal de Viçosa
Abstract: Soybean is considered one of the most profitable crops among the legumes grown worldwide. The occurrence of rust epidemics, caused by the fungus Phakopsora pachyrhizi, has contributed significantly to great yield losses and an abusive spray of fungicides. Within this context, this study investigated the potential of using a phosphite of nickel (Ni) and potassium (K) (referred to as induced resistance [IR] stimulus) to induce soybean resistance against infection by P. pachyrhizi. Plants were sprayed with water (control) or with the IR stimulus and non-inoculated or inoculated with P. pachyrhizi. Urediniospores germination was significantly reduced by 99% by the IR stimulus as its rates ranged from 2 to 15 mL/L in vitro. Rust severity was significantly reduced by 68-78% from 7 to 15 days after inoculation (dai). The area under the disease progress curve significantly decreased by 74% for IR stimulus-sprayed plants compared to water-sprayed plants. For inoculated plants, K and Ni foliar concentrations were significantly higher for IR stimulus treatment than for the control treatment. Infected plants sprayed with IR stimulus had their photosynthetic apparatus (great pool of photosynthetic pigments and lower values for some chlorophyll a fluorescence parameters) preserved, associated with less cellular damage (lower concentrations of malondialdehyde, hydrogen peroxide, and anion superoxide) and more production of phenolics and lignin than plants from the control treatment. In response to infection by P. pachyrhizi, the defense-related genes (PAL2.1, PAL3.1, CHIB1, LOX7, PR-1A, PR10, ICS1, ICS2, JAR, ETR1, ACS, ACO, and OPR3) were up-regulated from 7 to 15 dai for IR stimulus-sprayed plants in contrast to plants from the control treatment. Collectively, these findings provide a global picture of the enhanced capacity of IR stimulus-sprayed plants to efficiently cope with fungal infection at both biochemical and physiological levels without discarding the direct effect of this IR stimulus on urediniospores germination.

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