BnaC09.tfl1 controls determinate inflorescence trait in Brassica napus.

Determinate inflorescence is indeed a pivotal agricultural characteristic in crops, notably impacting the architecture modification of Brassica napus (AACC, 2n = 38). Previous study identified a crucial gene Bnsdt2 that encodes the transcription factor BnaC09.TFL1 (Terminal Flower 1). Here by two alleles were cloned and sequenced from indeterminate 2982 and determinate 4769, respectively, we found that BnaC09.TFL1 harbors two T/C and G/C non-synonymous mutations in exon 1, and contains sixty-six differences in a 1.9 Kb promoter sequence. Subsequently, BnaC09.TFL1 was introduced into B. napus 571 line by genetic complementation and overexpression, transgenic plants 571^CTO lines and 571^TClines were all restored to the indeterminate inflorescence. Interestingly, after BnaC09.TFL1 was knocked out in 'Westar', transgenic plants Westar^Tcr lines were mutated to determinate inflorescences. Additionally, a NIL-4769 line was constructed to evaluate the effect of BnaC09.TFL1 on agronomic traits of Brassica napus, the results demonstrated that BnaC09.tfl1 reduced the plant height and increased the branch number and branch thousand grain weight of Brassica napus. Finally, we performed RT-qPCR, GUS staining and subcellular localization experiments to analyze the expression pattern of BnaC09.TFL1, the results showed that the expression of BnaC09.TFL1 at shoot apex of NIL-4769 was higher than that of 4769, GUS activity was detected at apical of Arabidopsis thaliana and BnC09.TFL1-GFP was detected in cell membrane, nucleus and cytoplasm. 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.

Supplementary information: The online version contains supplementary material available at 10.1007/s11032-024-01503-7.