BnaC09.tfl1 controls determinate inflorescence trait in Brassica napus

Abstract Determinate inflorescence is a very important agronomic and plant architecture modified trait of Brassica napus (AACC, 2n = 38). Previous studies showed that determinate inflorescence trait could decrease plant height and lodging resistance in oilseed rape. A previous study identified a crucial gene Bnsdt2 that encodes the transcription factor BnaC09.TFL1 (Terminal Flower 1). In this study, we cloned and sequenced two alleles from two parents (indeterminate 2982 and determinate 4769, respectively). The results indicated that BnaC09.TFL1 harbors two T/C and G/C non-synonymous mutations in exon 1, and contains 66 differences in a 1.9 Kb promoter sequence. Subsequently, a NIL-BnaC09.TFL1IDT2982 line was built to verify the function of BnaC09.TFL1’s gene and its effect on agronomic traits of Brassica napus were designed. The results showed that BnaC09.tfl1 reduced the plant height and increased the branch number and branch thousand-grain weight of Brassica napus. Additionally, BnaC09.TFL1 was introduced into B. napus 571 lines (determinate inflorescence) by genetic complementation and overexpression, transgenic plants 571CTO lines and 571TClines were all restored to the indeterminate inflorescence. Intrerestingly, after BnaC09.TFL1 was knocked out in ‘Westar’ of Brassica napus, transgenic plants WestarTcr lines were mutated to determinate inflorescences. These findings demonstrate that BnaC09.tfl1 affects agronomic traits and controls the inflorescence characters of Brassica napus. Moreover, subcellular localization results showed the BnC09.TFL1 protein were located in the cell membrane, cytoplasm, and nucleus. Our findings provide a firm molecular foundation for the study of rapeseed’s molecular mechanism of determinate inflorescence formation, as well as theoretical guidance for the application of determinate inflorescence in rapeseed breeding.