Tolerance to Stress Combination in Tomato Plants: New Insights in the Protective Role of Melatonin

Abstract

Abiotic stresses such as drought, heat or salinity are major causes of yield loss worldwide. Recent studies have revealed that the acclimation of plants to a combination of different environmental stresses is unique and therefore cannot be directly deduced from studying the response of plants to each of the different stresses applied individually. The efficient detoxification of reactive oxygen species (ROS) is thought to play a key role in enhancing the tolerance of plants to abiotic stresses. Here, we report on the role of melatonin in the protection of the photosynthetic apparatus through the increase in ROS detoxification in tomato plants grown under the combination of salinity and heat, two of the most common abiotic stresses known to act jointly. Plants treated with exogenous melatonin showed a different modulation in the expression on some antioxidant-related genes and their related enzymes. More specifically, ascorbate peroxidase, glutathione reductase, glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase (APX, GR, GPX and Ph-GPX, resepctively) showed an antagonistic regulation as compared to plants that did not receive melatonin. This translated into a better antioxidant capacity and to a lesser ROS accumulation under stress combination. The performance of the photosynthesis parameters and the photosystems was also increased in plants treated with exogenous melatonin under the combination of salinity and heat. In accordance with these findings, tomato plants treated with melatonin were found to grow better under stress combination that the non-treated ones. Our study highlights the important role that exogenous melatonin plays in the acclimation of plants to a combination of two different abiotic stresses, and how this compound can specifically regulate oxidative stress-related genes and enzymes to increase plant tolerance.

Unveiling the transcriptome complexity of the High- and Low- Zinc & Iron accumulating Indian wheat (Triticum aestivum L.) cultivars

“…Number of proteins of CBL-interacting kinase, serine threonine kinase and wall-associated receptor kinase and Mitogen-activated kinase family were highly expressed wheat, involved in metal ion binding and its transportation serine/threonine kinase signalling, protein phosphorylation and response to stresses [Jin et al, 2016; Mao et al,2009; Shi et al, 2018 Hou et al, 2005; Kanneganti et al, 2008; Kumar et al, 2018; Wimalasekera et al, 2018]. Glutathione peroxidase and peroxidase family proteins expression indicates higher response to oxidative stress, glutathione peroxidase activity, metal ions binding & transportation activity [Alzahrani et al 2018; Martinez et al, 2018]. Interestingly, number of transcripts of zinc finger transcription factors and helicase-like transcription factor were expressed in HZFWGs showed their function in various transcription factor activity, sequence-specific DNA and metal ion binding and stress response [Bouain et al, 2014; Zang et al, 2016; Sarwat et al, 2018].…”

Unique miRNAs and their targets in tomato leaf responding to combined drought and heat stress

“…Melatonin, N-acetyl-5-methoxytryptamin, is a wellknown hormone that played roles in plant response to abiotic stress [13,14]. Endogenous melatonin could be triggered by both moderate drought (withdrawing water) and cold (2 ± 0.5°C) conditions for 48 h, which was involved in drought priming and cold stress response in barley [13].…”

“…Endogenous melatonin could be triggered by both moderate drought (withdrawing water) and cold (2 ± 0.5°C) conditions for 48 h, which was involved in drought priming and cold stress response in barley [13]. Martinez et al (2018) indicated that melatonin regulated genes and enzymes that were related to oxidative stress and ROS detoxification to improve tomato tolerance at combined salinity and heat [14]. In this study, significantly increased melatonin concentration was regarded as a responsive signal in tomato to the applied stresses, since the important roles of melatonin in plants at abiotic stress [13,14].…”

“…Martinez et al (2018) indicated that melatonin regulated genes and enzymes that were related to oxidative stress and ROS detoxification to improve tomato tolerance at combined salinity and heat [14]. In this study, significantly increased melatonin concentration was regarded as a responsive signal in tomato to the applied stresses, since the important roles of melatonin in plants at abiotic stress [13,14]. We detected miRNA using high-throughput sequencing (HTS) and identified the target genes through degradome analysis in tomato after 36 h of stress treatments with three biological replicates when the melatonin concentration significantly increased.…”

Trait discovery and editing in tomato

“…a single stress condition vs its control), there is a knowledge gap in the identification of QTLs involved in responses to combined stress. This aspect is of capital importance as it was shown that stress combination in tomato (biotic and/or abiotic) does not always have an additive effect regarding physiological, morphological, or biochemical responses compared with single stress (Rivero et al ., ; Bai et al ., ; Martinez et al ., ).…”