The BnTFL1-BnGF14nu-BnFD Module Regulates Flower Development and Plant Architecture in Brassica napus

Both flower development and plant architecture determine the efficiency of mechanized harvest and seed yield in Brassica napus. TERMINAL FLOWER 1 (AtTFL1) is a key regulator of flower development in Arabidopsis thaliana. Yet, the function and regulatory mechanism of TFL1 orthologs in B. napus remain unclear. Here, we found six BnTFL1 paralogs are present in the genome of the B. napus inbred line 'K407'. They exhibited a steadily increased expression during vernalization. CRISPR-Cas-induced mutagenesis of up to four BnTFL1 paralogs resulted in early flowering and the alteration of plant architecture, whereas seed yield was not influenced in BnTFL1 single, double, and triple mutants. Moreover, we showed that the six BnTFL1 paralogs have an additive and conserved effect on the regulation of several agronomic traits, including flowering time, total and terminal flower number, and plant architecture. Furthermore, we demonstrated that BnaA10.TFL1 regulates flower development by interacting with BnaA08.FD through the protein BnaA05.GF14nu, which resulted in the transcriptional repression of floral integrator and floral meristem identity genes. These findings provide new insights into the regulatory network of flower development and plant architecture and represent a promising target to modify flowering time and plant architecture without hampering seed yield in B. napus.