LAUSR

A preliminary study suggested that BrTT1, which encodes a WIP zinc finger transcription factor, was responsible for seed coat color formation in Dahuang. In this study, cloning and functional analyses of the BrTT1 gene were performed to verify this, where no difference was detected between the upstream/downstream sequences of the target gene. The full-length genomic sequence of BrTT1 gene (1804 bp), together with the upstream (1796 bp) and downstream sequences of the target gene (986 bp), was transformed into the A. thalianatt1 mutant, tt1-1, and the seed coat color was completely restored to brown. The CDS from yellow- and brown-seeded plants was also transformed into tt1-1 under control of the 35S promoter. Only the coding sequence from brown-seeded plants could restore the seed coat color of tt1-1, suggesting that mutations in the coding sequence affected the function of Brtt1 and led to the yellow-seeded trait in Dahuang. In addition, BrTT1 was localized in the nucleus. The aberrant expression of BrTT1 in the yellow-seeded material of Brassica rapa may cause the aberrant or absent expression of several important BrTT genes of the flavonoid biosynthetic pathway, then blocked proanthocyanidin accumulation and resulted in a transparent testa in Dahuang.