Abstract
Wheat is a vital crop. Its long-term sustainability and reliability are crucial for global food security. Drought is a major abiotic stress impacting growth of wheat. It is the main cause of low and inconsistent wheat yields. This study explores the role of transcription factors (TFs) and drought-responsive genes in the mechanisms controlling drought stress responses in six Egyptian wheat varieties (Misr1, Misr2, Misr3, Gemmiza9, Sids14, and Sakha95) under severe drought induced by polyethylene glycol. Drought stress was induced with PEG 6000 at 25%, applied for 3 and 6 days on 14-day-old wheat seedlings grown in a hydroponic system. Results showed that antioxidant enzyme activities (CAT, POD, and SOD) were significantly elevated, and H(2)O(2) concentrations decreased. After 3 days, proline accumulation notably increased in Gemmiza9 and Misr2, while MDA levels increased across all cultivars, indicating enhanced lipid peroxidation. After 6 days, proline content was significantly elevated in all cultivars, with continued increases in MDA and reductions in H(2)O(2) levels. This confirmed ongoing oxidative stress and adaptive responses. The qRT-PCR results revealed a time-dependent gene expression pattern under drought stress. After 3 days, Misr2 cultivar showed the highest induction of TaMYB73 (1.56-fold), TaWRKY13 (5.62-fold), and TaDHN2.1 (4.92-fold), while Sakha95 exhibited the strongest WDERB-2B expression (3.94-fold). After 6 days, TaMYB73 was highest in Misr3 (6.32-fold), while TaNAC2 peaked in Misr2 (5.98-fold), WDERB-2B in Sakha95 (13.45-fold), and TaDHN2.1 in Gemmiza9 (7.78-fold). TaOBF-1B was upregulated in all cultivars and reached its highest level in Misr1 (6.92-fold). This study categorizes Misr2 and Misr3 as tolerant cultivars, Misr1, Sakha95, and Gemmiza9 as semi-tolerant cultivars, and Sids14 as a sensitive cultivar. Our analysis identified key TF genes that regulate wheat's drought stress response network.