A Poaceae-specific DREB-A6 transcription factor TaDREB26-B regulates ABA responses and enhances drought stress tolerance in wheat

INTRODUCTION: Dehydration-responsive element-binding (DREB) transcription factors, members of the AP2/ERF superfamily, are pivotal regulators of stress-responsive gene expression by binding to DRE/CRT cis-elements. They represent promising targets for engineering crop resilience. OBJECTIVES: This study aims to elucidate the molecular mechanisms underlying ABA-mediated transcription and growth inhibition during drought stress in wheat, with the goal of identifying key drought-resistance genes. METHODS: The reverse genetics was employed in both Arabidopsis and wheat to investigate the drought-resistance function of TaDREB26-B. The regulatory interplay between TaDREB26-B and abscisic acid-responsive element-binding factors (ABFs), central components of ABA signaling, was dissected using Y1H, LUC, and EMSA assays. RESULTS: Co-localization with drought-related QTLs and stress-responsive expression profiles nominated TaDREB26 as a strong candidate drought-tolerance gene. Phylogenetic analysis revealed a Poaceae-specific clade within the DREB-A6 group harboring multiple stress-responsive DREBs. TaDREB26-B expression was rapidly upregulated by drought and ABA. Transgenic plants overexpressing TaDREB26-B exhibited enhanced drought tolerance and heightened ABA sensitivity. Mechanistically, TaDREB26-B activated AtABI4 in Arabidopsis and directly bound the promoter of TaABF2 to amplify the ABA signaling cascade in wheat. Furthermore, we identified a potential feedback regulatory module wherein TaDREB26-B activates TaABF2, while TaABF3 represses TaDREB26-B expression, fine-tuning ABA-responsive transcription. CONCLUSION: This work delineates a Poaceae-specific DREB clade and establishes TaDREB26-B as a prime regulator for improving drought tolerance. These findings provide novel molecular insights into the ABA-dependent transcriptional network governing stress responses and growth in wheat.