Enhancement of Non-Enzymatic Antioxidants in Eutrema salsugineum Under Salt Stress Depends on Salicylate Depletion.

Eutrema salsugineum is a model species for studying stress resistance, particularly extreme salinity, and is often compared with Arabidopsis thaliana. Previous research has shown that basal salicylic acid (SA) levels are significantly lower in E. salsugineum than in A. thaliana. In this study, subtractive hybridization revealed that SA-related genes were extensively induced in Arabidopsis but not in Eutrema. Using exogenous SA and the biosynthesis inhibitor paclobutrazol (PBZ), we further demonstrated that the low endogenous SA level in Eutrema significantly upregulates dehydroascorbate reductase (DHAR) and glutathione reductase (GR) gene expression, doubling the pools of total ascorbic acid and total glutathione. While SA treatment decreased the ratios of reduced ascorbic acid (ASA) to dehydroascorbate (DHA) and reduced glutathione (GSH) to oxidized glutathione (GSSG), PBZ treatment increased them, correspondingly modulating DHAR and GR activities and gene expression. The resulting enhancement of these key non-enzymatic antioxidants is a critical mechanism underpinning the superior salt tolerance of Eutrema.