The BnSEP-BnTFL1s module regulates inflorescence architecture based on light duration in Brassica napus L.

Rapeseed (Brassica napus L.) with determinate inflorescence (DTI) exhibit desirable traits, including reduced plant height, enhanced lodging resistance, and consistent maturity, making them valuable breeding resources. DTI is modulated by BnaA10.TFL1 and BnaC09.TFL1 (BnaA10/C09.TFL1) encode the TERMINAL FLOWER 1 protein, a key regulator of flowering time and meristem identity. However, the underlying functional and regulatory mechanisms remain unclear. In this study, we demonstrated that variations in the promoter region of BnaA10/C09.TFL1, rather than the coding region, contributed to the transition from indeterminate inflorescence (IDTI) to DTI in B. napus. Specifically, BnaA10.SEP inhibited BnaA10/C09.TFL1 expression by binding to the GT1-motif in the promoter region of BnaA10/C09.TFL1DTI, contributing to the IDTI phenotype under short-day conditions. Meanwhile, two novel DTI mutants were successfully generated through the simultaneous knockout of BnaA10/C09.TFL1 using the CRISPR/Cas9 system. Furthermore, BnaA10/C09.TFL1 and its homolog BnaA02.FT interacted with BnaA07.14-3-3 instead of directly binding to BnaA08.FD to regulate the development of different inflorescence architectures. Overall, the BnaA10.SEP–BnaA10/C09.TFL1–BnaA07.14-3-3–BnaA08.FD module revealed a new mechanism for DTI formation and a promising strategy for modifying inflorescence architecture traits in B. napus.