Search

Plants are frequently exposed to a plethora of unfavourable climatic catastrophes, be it abiotic or biotic stresses, viz., salinity, water (drought or water logging), extreme temperature, heavy metal, nutrient deficiency, ozone, pathogen attack, etc., which badly affect the yield and productivity of crops. Plants, as part of their defence machinery, employ different tolerance mechanisms to survive under adverse conditions. In addition to other stress responses, the mitogen-activated protein kinase (MAPK) signalling cascade and accumulation of glutathione (GSH) are two important aspects of plant defence response. Induction of the MAPK cascade is one of the earliest responses when a plant is under any environmental stress, and there is documentary evidence of this signalling pathway, in turn, regulating various phytohormone-signalling networks and other defence-related pathways during stress. Similarly, GSH being a low molecular weight metabolite also has a key role in environmental stress tolerance. It is known to be involved in multi-step interactions with various phytohormones, many signalling molecules, and redox molecules such as reactive oxygen species (ROS). This review provides an outline on GSH-MAPK crosstalk to better understand its role in the context of defence signalling in plants.

Glutathione (GSH) plays a fundamental role in plant defense. Recent reports showed that enhanced GSH content activates mitogen-activated protein kinases (MPKs). However, the molecular mechanism behind this GSH-mediated MPKs expression during environmental challenges is unexplored. Here, we found that under control and combined abiotic stress-treated conditions, GSH feeding activates MPK3 expression in Arabidopsis thaliana by inducing its promoter, as established through the promoter activation assay. Additionally, transgenic A. thaliana overexpressing the LeMPK3 gene (AtMPK3 line) showed increased γ-ECS expression, which was decreased in mpk3, the MPK3-depleted mutant. An in-gel kinase assay exhibited hyperphosphorylation of Myelin Basic Protein (MBP) in the GSH-fed AtMPK3 transgenic line. Under control and combined abiotic stress treated conditions, expression of transcription factor WRKY40 binding to MPK3 promoter was up-regulated under enhanced GSH condition. Interestingly, GSH feeding was rendered ineffective in altering MPK3 expression in the Atwrky40 mutant, emphasizing the involvement of WRKY40 in GSH-MPK3 interplay. This was further confirmed by a wrky40 co-transformation assay. The immunoprecipitation assay followed by ChIP-qPCR showed a significant increase in the binding of WRKY40 to MPK3 promoter, which further established MPK3-WRKY40 association upon GSH feeding. In conclusion, this study demonstrated that GSH modulates MPK3 expression via WRKY40 in response to stress. • Deciphering the role of GSH-MPK3 interplay in plant defense system during environmental stress. • Altered GSH content in plants positively modulates the expression of MPK3 both at transcript and protein level. • This modulation was observed to take place via WRKY40 transcription factor. • Elevated GSH level increased the WRKY40 binding to MPK3 promoter, consequently activating MPK3 during stress. [ABSTRACT FROM AUTHOR]

Grass pea has the potential to become a miracle crop if the stigma attached to it as a toxic plant is ignored. In light of the following, we conducted transcriptome analyses on the high and low ODAP-containing cultivars i.e., Nirmal and Bidhan respectively in both normal and salt stress conditions. In this study, genes that work upstream and downstream to β-ODAP have been found. Among these genes, AAO3 and ACL5 were related to ABA and polyamine biosynthesis, showing the relevance of ABA and polyamines in boosting the β-ODAP content in Nirmal. Elevated β-ODAP levels in salt stress-treated Bidhan may have evolved tolerance by positively regulating the expression of genes involved in phenylpropanoid and jasmonic acid biosynthesis. Although the concentration of β-ODAP in Bidhan increased under salt stress, it was lower than in stress-treated Nirmal. Despite this, the expression of stress-related genes that work downstream to β-ODAP was found higher in stress-treated Bidhan. This could be because stress-treated Nirmal has lower GSH, proline, and higher H 2 O 2 , resulting in the development of severe oxidative stress. Overall, our research not only identified new genes linked with β-ODAP, but also revealed the molecular mechanism by which a low β-ODAP-containing cultivar developed tolerance against salinity stress. • Bidhan is a low-β-ODAP cultivar having salinity stress tolerance. • β-ODAP production is largely regulated by genes involved in ABA and polyamine biosynthesis. • Elevated β-ODAP in stress-treated Bidhan develops tolerance by positive regulation of phenylpropanoid and jasmonic acid biosynthesis related genes. • Elevated level of GSH and proline provides salinity stress tolerance to Bidhan. [ABSTRACT FROM AUTHOR]