Genome-wide identification of dehydroascorbate reductase genes in Avena sativa and functional characterization of AsDHAR1 in seed aging responses

Seed aging is a major factor affecting seed quality and field germination performance. Dehydroascorbate reductase (DHAR), a key enzyme in the ascorbate-glutathione cycle, helps plants scavenge reactive oxygen species under abiotic stress, but its role in regulating oat seed vigor remains unclear. Here, we identified six DHAR genes in oat and found that AsDHAR1 was the primary candidate because its transcript abundance was significantly higher in aged seeds at several imbibition stages and was highest in seeds among the tissues examined. Functional analyses combining AsDHAR1 overexpression in Arabidopsis thaliana with post-aging tobacco rattle virus-mediated gene silencing directly in oat indicated that AsDHAR1 contributes to seed vigor regulation. After aging treatment, seed germination percentage was maintained at approximately 76% in the overexpression line compared with 65% in the control, whereas post-aging silencing of AsDHAR1 in oat reduced germination from approximately 52% to 29%. Physiological analyses further showed that AsDHAR1 overexpression reduced hydrogen peroxide (H₂O₂) accumulation, enhanced several antioxidant enzyme activities, and altered multiple components of the ascorbate-glutathione cycle, whereas silencing reduced DHAR activity and suppressed the expression of antioxidant-related genes during subsequent germination. These results suggest that AsDHAR1 contributes to redox homeostasis and seed vigor maintenance. This study provides new insights into the role of AsDHAR1 in oat seed aging and advances the understanding of the molecular basis of seed vigor regulation.