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18 pages, 4255 KiB

Open AccessArticle

Improvement of Seed Germination under Salt Stress via Overexpressing Caffeic Acid O-methyltransferase 1 (SlCOMT1) in Solanum lycopersicum L.

by Lianjing Ge, Xiaoyu Yang, Yue Liu, Huimeng Tang, Qifang Wang, Shunpeng Chu, Jinxiang Hu, Ning Zhang and Qinghua Shi

Int. J. Mol. Sci. 2023, 24(1), 734; https://doi.org/10.3390/ijms24010734 - 01 Jan 2023

Cited by 7 | Viewed by 1870

Abstract

Melatonin (MT) is a phytohormone-like substance and is profoundly involved in modulating nearly all aspects of plant development and acclimation to environmental stressors. However, there remain no studies about the effects of MT on tomato seed germination under salt stress. Here we reported [...] Read more.

Melatonin (MT) is a phytohormone-like substance and is profoundly involved in modulating nearly all aspects of plant development and acclimation to environmental stressors. However, there remain no studies about the effects of MT on tomato seed germination under salt stress. Here we reported that the overexpression of caffeic acid O-methyltransferase 1 (SlCOMT1) significantly increased both MT content and salt tolerance in the germinated seeds of a transgenic tomato relative to wild type (WT) samples. Physiological investigation showed higher amylase activity in the stressed overexpression seeds than WT, leading to the promoted starch decomposition and enhanced soluble sugar content. The stimulated production of osmolytes and enhanced activities of SOD, POD, and CAT, together with the significant reduction in H₂O₂ and O₂^·− accumulation, were revealed in the stressed overexpression seeds relative to WT, largely accounting for their lower membrane lipid peroxidation. qPCR assay showed that, upon salt stress, the transcript abundance of hub genes related to germination (SlCYP707A1, SlABA1, SlGA3ox2 and SlGA2ox4) and stress tolerance (SlCDPK1, SlWRKY33 and SlMAPK1) were distinctly altered in the overexpression samples when compared to WT, providing a molecular basis for MT-mediated improvement of seed salt tolerance. Altogether, our observations shed new insights into biological functions of SlCOMT1 and could expand its utilization in genetic improvement of tomato salt tolerance in future. Full article

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

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16 pages, 4375 KiB

Open AccessArticle

Melatonin Enhances Drought Tolerance in Rice Seedlings by Modulating Antioxidant Systems, Osmoregulation, and Corresponding Gene Expression

by Chengke Luo, Weifang Min, Maryam Akhtar, Xuping Lu, Xiaorong Bai, Yinxia Zhang, Lei Tian and Peifu Li

Int. J. Mol. Sci. 2022, 23(20), 12075; https://doi.org/10.3390/ijms232012075 - 11 Oct 2022

Cited by 17 | Viewed by 1875

Abstract

Rice is the third largest food crop in the world, especially in Asia. Its production in various regions is affected to different degrees by drought stress. Melatonin (MT), a novel growth regulator, plays an essential role in enhancing stress resistance in crops. Nevertheless, [...] Read more.

Rice is the third largest food crop in the world, especially in Asia. Its production in various regions is affected to different degrees by drought stress. Melatonin (MT), a novel growth regulator, plays an essential role in enhancing stress resistance in crops. Nevertheless, the underlying mechanism by which melatonin helps mitigate drought damage in rice remains unclear. Therefore, in the present study, rice seedlings pretreated with melatonin (200 μM) were stressed with drought (water potential of −0.5 MPa). These rice seedlings were subsequently examined for their phenotypes and physiological and molecular properties, including metabolite contents, enzyme activities, and the corresponding gene expression levels. The findings demonstrated that drought stress induced an increase in malondialdehyde (MDA) levels, lipoxygenase (LOX) activity, and reactive oxygen species (ROS, e.g., O₂⁻ and H₂O₂) in rice seedlings. However, the melatonin application significantly reduced LOX activity and the MDA and ROS contents (O₂⁻ production rate and H₂O₂ content), with a decrease of 29.35%, 47.23%, and (45.54% and 49.33%), respectively. It activated the expression of ALM1, OsPOX1, OsCATC, and OsAPX2, which increased the activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), respectively. Meanwhile, the melatonin pretreatment enhanced the proline, fructose, and sucrose content by inducing OsP5CS, OsSUS7, and OsSPS1 gene expression levels. Moreover, the melatonin pretreatment considerably up-regulated the expression levels of the melatonin synthesis genes TDC2 and ASMT1 under drought stress by 7-fold and 5-fold, approximately. These improvements were reflected by an increase in the relative water content (RWC) and the root-shoot ratio in the drought-stressed rice seedlings that received a melatonin application. Consequently, melatonin considerably reduced the adverse effects of drought stress on rice seedlings and improved rice’s ability to tolerate drought by primarily boosting endogenous antioxidant enzymes and osmoregulation abilities. Full article

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

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17 pages, 3094 KiB

Open AccessArticle

Exogenous Melatonin Reprograms the Rhizosphere Microbial Community to Modulate the Responses of Barley to Drought Stress

by Fan Ye, Miao Jiang, Peng Zhang, Lei Liu, Shengqun Liu, Chunsheng Zhao and Xiangnan Li

Int. J. Mol. Sci. 2022, 23(17), 9665; https://doi.org/10.3390/ijms23179665 - 26 Aug 2022

Cited by 12 | Viewed by 1895

Abstract

The rhizospheric melatonin application-induced drought tolerance has been illuminated in various plant species, while the roles of the rhizosphere microbial community in this process are still unclear. Here, the diversity and functions of the rhizosphere microbial community and related physiological parameters were tested [...] Read more.

The rhizospheric melatonin application-induced drought tolerance has been illuminated in various plant species, while the roles of the rhizosphere microbial community in this process are still unclear. Here, the diversity and functions of the rhizosphere microbial community and related physiological parameters were tested in barley under the rhizospheric melatonin application and drought. Exogenous melatonin improved plant performance under drought via increasing the activities of non-structural carbohydrate metabolism enzymes and activating the antioxidant enzyme systems in barley roots under drought. The 16S/ITS rRNA gene sequencing revealed that drought and melatonin altered the compositions of the microbiome. Exogenous melatonin increased the relative abundance of the bacterial community in carbohydrate and carboxylate degradation, while decreasing the relative abundance in the pathways of fatty acid and lipid degradation and inorganic nutrient metabolism under drought. These results suggest that the effects of melatonin on rhizosphere microbes and nutrient condition need to be considered in its application for crop drought-resistant cultivation. Full article

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

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19 pages, 1746 KiB

Open AccessArticle

Melatonin Protects Tobacco Suspension Cells against Pb-Induced Mitochondrial Dysfunction

by Agnieszka Kobylińska and Małgorzata Maria Posmyk

Int. J. Mol. Sci. 2021, 22(24), 13368; https://doi.org/10.3390/ijms222413368 - 13 Dec 2021

Cited by 4 | Viewed by 2167

Abstract

Recent studies have shown that melatonin is an important molecule in plant physiology. It seems that the most important is that melatonin effectively eliminates oxidative stress (direct and indirect antioxidant) and switches on different defence strategies (preventive and interventive actions) during environmental stresses. [...] Read more.

Recent studies have shown that melatonin is an important molecule in plant physiology. It seems that the most important is that melatonin effectively eliminates oxidative stress (direct and indirect antioxidant) and switches on different defence strategies (preventive and interventive actions) during environmental stresses. In the presented report, exogenous melatonin potential to protect Nicotiana tabacum L. line Bright Yellow 2 (BY-2) exposed to lead against death was examined. Analyses of cell proliferation and viability, the level of intracellular calcium, changes in mitochondrial membrane potential (ΔΨm) as well as possible translocation of cytochrome c from mitochondria to cytosol and subsequent caspase-like proteolytic activity were conducted. Our results indicate that pretreatment BY-2 with melatonin protected tobacco cells against mitochondrial dysfunction and caspase-like activation caused by lead. The findings suggest the possible role of this indoleamine in the molecular mechanism of mitochondria, safeguarding against potential collapse and cytochrome c release. Thus, it seems that applied melatonin acted as an effective factor, promoting survival and increasing plant tolerance to lead. Full article

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

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27 pages, 4450 KiB

Open AccessArticle

Melatonin Application Modifies Antioxidant Defense and Induces Endoreplication in Maize Seeds Exposed to Chilling Stress

by Izabela Kołodziejczyk, Andrzej Kaźmierczak and Małgorzata M. Posmyk

Int. J. Mol. Sci. 2021, 22(16), 8628; https://doi.org/10.3390/ijms22168628 - 11 Aug 2021

Cited by 19 | Viewed by 2306

Abstract

The aim of the study was to demonstrate the biostimulating effect of exogenous melatonin (MEL) applied to seeds via hydroconditioning. It was indicated that only well-chosen application technique and MEL dose guarantees success concerning seed germination and young seedlings growth under stress conditions. [...] Read more.

The aim of the study was to demonstrate the biostimulating effect of exogenous melatonin (MEL) applied to seeds via hydroconditioning. It was indicated that only well-chosen application technique and MEL dose guarantees success concerning seed germination and young seedlings growth under stress conditions. For maize seed, 50 μM of MEL appeared to be the optimal dose. It improved seed germination and embryonic axes growth especially during chilling stress (5 °C/14 days) and during regeneration after its subsided. Unfortunately, MEL overdosing lowered IAA level in dry seeds and could disrupt the ROS-dependent signal transduction pathways. Very effective antioxidant MEL action was confirmed by low level of protein oxidative damage and smaller quantity of lipid oxidation products in embryonic axes isolated from seeds pre-treated with MEL and then exposed to cold. The stimulatory effects of MEL on antioxidant enzymes: SOD, APX and GSH-PX and on GST-a detoxifying enzyme, was also demonstrated. It was indicated for the first time, that MEL induced defence strategies against stress at the cytological level, as appearing endoreplication in embryonic axes cells even in the seeds germinating under optimal conditions (preventive action), but very intensively in those germinating under chilling stress conditions (intervention action), and after stress removal, to improve regeneration. Full article

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

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Review

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21 pages, 2334 KiB

Open AccessReview

Interaction between Melatonin and NO: Action Mechanisms, Main Targets, and Putative Roles of the Emerging Molecule NOmela

by Sara E. Martínez-Lorente, Miriam Pardo-Hernández, José M. Martí-Guillén, María López-Delacalle and Rosa M. Rivero

Int. J. Mol. Sci. 2022, 23(12), 6646; https://doi.org/10.3390/ijms23126646 - 14 Jun 2022

Cited by 13 | Viewed by 2439

Abstract

Melatonin (MEL), a ubiquitous indolamine molecule, has gained interest in the last few decades due to its regulatory role in plant metabolism. Likewise, nitric oxide (NO), a gasotransmitter, can also affect plant molecular pathways due to its function as a signaling molecule. Both [...] Read more.

Melatonin (MEL), a ubiquitous indolamine molecule, has gained interest in the last few decades due to its regulatory role in plant metabolism. Likewise, nitric oxide (NO), a gasotransmitter, can also affect plant molecular pathways due to its function as a signaling molecule. Both MEL and NO can interact at multiple levels under abiotic stress, starting with their own biosynthetic pathways and inducing a particular signaling response in plants. Moreover, their interaction can result in the formation of NOmela, a very recently discovered nitrosated form of MEL with promising roles in plant physiology. This review summarizes the role of NO and MEL molecules during plant development and fruit ripening, as well as their interactions. Due to the impact of climate-change-related abiotic stresses on agriculture, this review also focuses on the role of these molecules in mediating abiotic stress tolerance and the main mechanisms by which they operate, from the upregulation of the entire antioxidant defense system to the post-translational modifications (PTMs) of important molecules. Their individual interaction and crosstalk with phytohormones and H₂S are also discussed. Finally, we introduce and summarize the little information available about NOmela, an emerging and still very unknown molecule, but that seems to have a stronger potential than MEL and NO separately in mediating plant stress response. Full article

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

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24 pages, 3721 KiB

Open AccessReview

Melatonin Modulates Plant Tolerance to Heavy Metal Stress: Morphological Responses to Molecular Mechanisms

by Md. Najmol Hoque, Md. Tahjib-Ul-Arif, Afsana Hannan, Naima Sultana, Shirin Akhter, Md. Hasanuzzaman, Fahmida Akter, Md. Sazzad Hossain, Md. Abu Sayed, Md. Toufiq Hasan, Milan Skalicky, Xiangnan Li and Marián Brestič

Int. J. Mol. Sci. 2021, 22(21), 11445; https://doi.org/10.3390/ijms222111445 - 23 Oct 2021

Cited by 79 | Viewed by 6797

Abstract

Heavy metal toxicity is one of the most devastating abiotic stresses. Heavy metals cause serious damage to plant growth and productivity, which is a major problem for sustainable agriculture. It adversely affects plant molecular physiology and biochemistry by generating osmotic stress, ionic imbalance, [...] Read more.

Heavy metal toxicity is one of the most devastating abiotic stresses. Heavy metals cause serious damage to plant growth and productivity, which is a major problem for sustainable agriculture. It adversely affects plant molecular physiology and biochemistry by generating osmotic stress, ionic imbalance, oxidative stress, membrane disorganization, cellular toxicity, and metabolic homeostasis. To improve and stimulate plant tolerance to heavy metal stress, the application of biostimulants can be an effective approach without threatening the ecosystem. Melatonin (N-acetyl-5-methoxytryptamine), a biostimulator, plant growth regulator, and antioxidant, promotes plant tolerance to heavy metal stress by improving redox and nutrient homeostasis, osmotic balance, and primary and secondary metabolism. It is important to perceive the complete and detailed regulatory mechanisms of exogenous and endogenous melatonin-mediated heavy metal-toxicity mitigation in plants to identify potential research gaps that should be addressed in the future. This review provides a novel insight to understand the multifunctional role of melatonin in reducing heavy metal stress and the underlying molecular mechanisms. Full article

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

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40 pages, 4147 KiB

Open AccessReview

Melatonin and Phytomelatonin: Chemistry, Biosynthesis, Metabolism, Distribution and Bioactivity in Plants and Animals—An Overview

by Giuseppe Mannino, Carlo Pernici, Graziella Serio, Carla Gentile and Cinzia M. Bertea

Int. J. Mol. Sci. 2021, 22(18), 9996; https://doi.org/10.3390/ijms22189996 - 16 Sep 2021

Cited by 67 | Viewed by 17510

Abstract

Melatonin is a ubiquitous indolamine, largely investigated for its key role in the regulation of several physiological processes in both animals and plants. In the last century, it was reported that this molecule may be produced in high concentrations by several species belonging [...] Read more.

Melatonin is a ubiquitous indolamine, largely investigated for its key role in the regulation of several physiological processes in both animals and plants. In the last century, it was reported that this molecule may be produced in high concentrations by several species belonging to the plant kingdom and stored in specialized tissues. In this review, the main information related to the chemistry of melatonin and its metabolism has been summarized. Furthermore, the biosynthetic pathway characteristics of animal and plant cells have been compared, and the main differences between the two systems highlighted. Additionally, in order to investigate the distribution of this indolamine in the plant kingdom, distribution cluster analysis was performed using a database composed by 47 previously published articles reporting the content of melatonin in different plant families, species and tissues. Finally, the potential pharmacological and biostimulant benefits derived from the administration of exogenous melatonin on animals or plants via the intake of dietary supplements or the application of biostimulant formulation have been largely discussed. Full article

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

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