GLUTATHIONE S-TRANSFERASE GENES MEDIATE CROSSTALK BETWEEN OXIDATIVE STRESS AND ETHYLENE SIGNALING TO MODULATE STRESS RESPONSES IN TOMATO

Abiotic stresses significantly impair plant growth, reducing yield and fruit quality. As sessile organisms, plants respond to stress by producing reactive oxygen species (ROS), which function as signalling molecules to activate adaptive defences. However, excessive ROS accumulation can cause cellular damage. To counteract oxidative stress, plants utilize diverse antioxidants and antioxidant enzymes. Among these, glutathione S transferases (GSTs) form a multigene protein superfamily crucial for redox homeostasis and stress response. GSTs exhibit diverse cellular mechanisms and metabolic functions and are key regulators in plant stress adaptation pathways. Their expression is coordinately regulated with ethylene signalling pathway genes, including ERF transcription factors. Previous studies indicate that ethylene promotes glutathione (GSH) synthesis, while GSH can influence ethylene production. Furthermore, ERFs directly regulate GST gene expression, contributing to stress responses. Our research aims to elucidate the functional interplay between GST and ERF gene networks in modulating tomato's environmental stress responses, providing a molecular foundation for targeted breeding. Through comprehensive bioinformatic analysis, we identified 90 GST genes in tomato, distributed across multiple subclasses. Most members exhibit stress responsive expression patterns and tissue-specific regulation. Analysis of stress tolerance expression quantitative trait loci (eQTLs) in wild tomato accessions revealed coordinated upregulation of GST and ERF genes. This establishes a basis for enhancing stress tolerance in elite lines via marker-assisted introgression of these QTLs. Notably, CRISPR/Cas9 knock-out of tomato ERF genes increased GST gene expression and enhanced drought tolerance. Complementarily, overexpression of a tomato GST gene in tobacco improved drought and salinity tolerance, impacting the ascorbate glutathione cycle. Our current efforts focus on developing a comprehensive CRISPR-edited tomato mutant library targeting GST and ERF loci. This resource will enable functional dissection of stress resilience mechanisms and accelerate the development of climate-adapted crops.