Deciphering Drought Response Mechanisms in Oat Through Comprehensive Transcriptomic and Physiological Analysis

Oat, an important cereal and forage crop, is significantly affected by drought stress during production. However, the molecular mechanisms underlying oat’s response to drought stress remain largely unknown. In this study, K-means clustering classified 28 oat varieties into drought-tolerant (Muda, Mengshi No. 1) and drought-sensitive (Heike, Haywire) groups, with grey relational analysis further verifying MS as the most drought-tolerant and HK as the most drought-sensitive variety. Under drought stress, drought-tolerant and drought-sensitive varieties showed notable differences in leaf chlorophyll content, osmoregulation substances, and the activities of antioxidant enzymes. Transcriptomic analysis showed that 1915 differentially expressed genes (DEGs) were shared among all comparisons between treatment groups and the control group. KEGG pathway analysis revealed enrichment in pathways such as plant–pathogen interactions, plant hormone signal transduction, and starch and sucrose metabolism. In the signal transduction of plant hormones, eight PP2C genes associated with ABA signaling were increased, indicating that oats might respond to drought by enhancing metabolic activities via the ABA signaling pathway. WGCNA identified gene modules significantly associated with physiological traits. Notably, Mantel tests revealed that six core genes exhibited a positive correlation with CAT activity in the drought-tolerant variety, while showing an opposite trend in the sensitive variety. This study provides insights into the mechanisms of drought tolerance in oats and aids in the molecular breeding of drought-tolerant varieties.