Genome-wide identification of the DREB gene family and functional exploration of BnaA6.TINY under drought stress response in Brassica napus L.

According to the literature, DREB genes play crucial roles in conferring resistance to various abiotic stresses in numerous crop species. However, systematic identification and functional analysis of DREB genes in B. napus have remained limited. In this study, 128 DREB genes were identified in the B. napus genome and classified into 6 subfamilies based on their structural characteristics and phylogenetic relationships. Intragenomic collinearity analysis revealed that numerous segmental duplication events had occurred and that these genes were subject to purifying selection. GUS staining and qRT-PCR analyses further revealed that BnaA6.TINY (BnaDREB34) is constitutively expressed in various tissues and is significantly upregulated under abiotic stress. Transient expression assays demonstrated that BnaA6.TINY is localized in the nucleus, and its C-terminal region exhibits robust transcriptional activation activity in yeast cells. Overexpression of BnaA6.TINY significantly increased drought tolerance in both Arabidopsis and B. napus, which was accompanied by increased proline accumulation and reduced levels of reactive oxygen species (ROS). Yeast one-hybrid (Y1H) and dual-luciferase assays showed that BnaA6.TINY specifically binds to the DRE (dehydration-responsive element) motif in the BnaA9.PP2C58 promoter, thereby activating its expression and promoting stomatal closure to enhance drought tolerance. In summary, this study provides a comprehensive overview of the DREB gene family in B. napus and identifies BnaA6.TINY as a key regulator of drought stress responses, highlighting its potential as a promising target for molecular breeding to enhance stress tolerance in B. napus.