Comparative physiological and transcriptomic profiling suggests key pathways in oat drought tolerance

Oat (Avena sativa L.) is a valuable cereal crop, particularly in arid and semi-arid regions, where drought stress severely limits yield. Understanding the physiological and molecular mechanisms underlying drought tolerance in oat is essential for improving its resilience and productivity. This study compared the physiological and transcriptomic responses of a drought-tolerant oat cultivar (DA92-2F6, D) and a drought-sensitive cultivar (Longyan No. 3, L3) under PEG-induced drought stress at 0, 6, 24, and 72 h. Drought stress led to significant increases in malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels, with the most pronounced accumulation observed in L3. In contrast, cultivar D maintained significantly higher antioxidant enzyme activities (CAT, POD, SOD, APX; P < 0.05), better photosynthetic performance (transpiration and net photosynthesis rates), and greater chlorophyll retention than L3. Transcriptome analysis revealed four key drought-responsive pathways: starch and sucrose metabolism, phenylpropanoid biosynthesis, plant hormone signaling, and photosynthesis regulation. Candidate genes associated with drought response included CWINV, GPI, SPP, UGP, SS, and SBE (carbohydrate metabolism); PAL, OMT1, 4CL, and CCR (phenylpropanoid biosynthesis); and SnRK2, HAB2, GBF4, JAZ1, and MYC2 (hormone signaling). Our integrated physiological and transcriptomic analysis provides new insights into oat drought responses, identifies potential genetic markers for drought tolerance, and offers a foundation for breeding more resilient oat varieties.