The BnSEP-BnTFL1s module regulates inflorescence architecture based on light duration in <i>Brassica napus</i> L

Rapeseed (<i>Brassica napus</i> L.) with determinate inflorescence (DTI) exhibits desirable traits, including reduced plant height, enhanced lodging resistance, and consistent maturity, making them valuable breeding resources. DTI is modulated by <i>BnaA10.TFL1</i> and <i>BnaC09.TFL1</i> (<i>BnaA10/C09.TFL1</i>), which encode the <i>TERMINAL FLOWER 1</i> 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 <i>BnaA10/C09.TFL1</i>, rather than the coding region, contributed to the transition from indeterminate inflorescence (IDTI) to DTI in <i>B. napus</i>. Specifically, <i>BnaA10.SEP</i> inhibited <i>BnaA10/C09.TFL1</i> expression by binding to the GT1-motif in the promoter region of <i>BnaA10/C09.TFL1</i> ^{<b><i>DTI</i></b>} , contributing to the IDTI phenotype under short-day conditions. Meanwhile, two novel DTI mutants were successfully generated through the simultaneous knockout of <i>BnaA10/C09.TFL1</i> 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 <i>B. napus</i>.