Drought stress-induced enzyme activity and mdar and apx gene expression in tolerant and susceptible genotypes of Eleusine coracana (L.)

Abstract

Drought is a major constraint limiting agricultural productivity worldwide. Exposure to drought results in altered physiology of plants and causes oxidative stress. The aim of this study was to evaluate genotypic differences in oxidative stress markers and transcript levels of genes encoding ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDAR) from two finger millet (Eleusine coracana L.) varieties differing in their stress tolerance potential. Seedlings of PR202, a stress-tolerant variety, and PES400, a susceptible variety, were subjected to different polyethylene glycol 6000 (PEG-6000) concentrations (0, 5, 10, 15, and 20%). Increases in activity of APX and MDAR were observed under stress, with maximal increases being recorded at 15 and 20% PEG-6000. At these PEG-6000 levels, PES400 showed comparatively higher accumulations of malondialdehyde and hydrogen peroxide and a lower APX:MDAR ratio than PR202. Adaptive stress response was better in PR202 than in PES400, demonstrating the stress-tolerant character of PR202. Under oxidative stress, the expression of genes encoding APX and MDAR was positively correlated with the respective enzyme activities. The results demonstrated that 15 and 20% PEG-6000 concentrations are optimum for revealing differences in stress response between PR202 and PES400. The results of this study will be useful in understanding the expression of drought-responsive genes in E. coracana.