Natural variation in BnaA9.NF-YA7 contributes to drought tolerance in Brassica napus L

Rapeseed (Brassica napus) is one of the important oil crops worldwide. Its production is often threatened by drought stress. Here, we identify a transcription factor (BnaA9.NF-YA7) that negatively regulates drought tolerance through genome-wide association study in B. napus. The presence of two SNPs within a CCAAT cis element leads to downregulation of BnaA9.NF-YA7 expression. In addition, the M63I (G-to-C) substitution in the transactivation domain can activate low level expression of BnaA4.DOR, which is an inhibitory factor of ABA-induced stomatal closure. Furthermore, we determine that Bna.ABF3/4s directly regulate the expression of BnaA9.NF-YA7, and BnaA9.NF-YA7 indirectly suppresses the expression of Bna.ABF3/4s by regulation of Bna.ASHH4s. Our findings uncover that BnaA9.NF-YA7 serves as a supplementary role for ABA signal balance under drought stress conditions, and provide a potential molecular target to breed drought-tolerant B. napus cultivars.