Fine Mapping and Functional Verification of the Brdt1 Gene Controlling Determinate Inflorescence in Brassica rapa L.

Abstract

Brassica rapa, a major oilseed crop in high-altitude areas, is well known for its indeterminate inflorescences. However, this experiment revealed an intriguing anomaly within the plot: a variant displaying a determinate growth habit (520). Determinate inflorescences have been recognized for their role in the genetic enhancement of crops. In this study, a genetic analysis in a determinate genotype (520) and an indeterminate genotype (515) revealed that two independently inherited recessive genes (Brdt1 and Brdt2) are responsible for the determinate trait. BSA-seq and SSR markers were employed to successfully locate the Brdt1 gene, which is localized within an approximate region 72.7 kb between 15,712.9 kb and 15,785.6 kb on A10. A BLAST analysis of these candidate intervals revealed that Bra009508 (BraA10.TFL1) shares homology with the A. thaliana TFL1 gene. Then, BraA10.TFL1 (gene from the indeterminate phenotype) and BraA10.tfl1 (gene from the determinate phenotype) were cloned and sequenced, and the results indicated that the open reading frame of the alleles comprises 537 bp. Using qRT-PCR, it was determined that BraA10.TFL1 expression levels in shoot apexes were significantly higher in NIL-520 compared to 520. To verify the function of BraA10.TFL1, the gene was introduced into the determinate A. thaliana tfl1 mutant, resulting in the restoration of indeterminate traits. These findings demonstrate that BraA10.tfl1 is a gene that controls the determinate inflorescence trait. Overall, the results of this study provide a theoretical foundation for the further investigation of determinate inflorescence.