Antioxidant Enzyme Gene Expression in Barley under Drought Stress

Reactive oxygen species (ROS), redox molecules primarily generated in organisms, are particularly significant in photosynthetic cells. Here, ROS production must be tightly controlled to avoid detrimental side effects on cellular functions. Plants employ a suite of ROS-scavenging enzymes, including ascorbate peroxidase (APX), catalase (CAT), dehydroascorbate reductase (DHAR), and peroxiredoxin (PRX), to combat oxidative stress. These antioxidant enzymes are strategically localized within different compartments of plant cells, working in concert to neutralize reactive oxygen species (ROS). CAT and APX play a crucial role in detoxifying hydrogen peroxide (H2O2). While CAT directly breaks down H2O2, APX requires ascorbic acid (AsA) as a cofactor for its activity. Peroxiredoxin (PRX) employs a distinct mechanism, utilizing thiol-mediated pathways independent of ascorbate to reduce both H2O2 and organic hydroperoxides. In this study, the analysis of enzymes activities was performed on five contrasting Iranian barley cultivars under drought stress at reproductive stage. Gene expression analysis revealed that seven antioxidant genes were accumulated in the flag leaf, awn, peduncle, and penultimate tissues at reproductive stage after being subjected to drought stress. Furthermore, most of antioxidant gene expression were up-regulated in response to drought stress in the four tissues. Our results revealed that the genotypes G1, G3, and G5 responded appropriately to drought stress at seed filling stage. Among the studied tissues, penultimate showed the most up-regulation of antioxidant gene in response to stress. To elucidate the mechanisms of drought tolerance in barley during grain filling, we conducted a comprehensive analysis of gene expression related to key antioxidant enzymes in the ASA-GSH cycle. By comparing these expressions across the flag leaves, peduncle, penultimate, and awn, we obtained significant differences in physiological and metabolic responses to drought stress among genotypes. This study will provide valuable insights into the distinct drought tolerance strategies employed by different tissues, ultimately contributing to a deeper understanding of drought tolerance in barley.