Identification of bHLHs based on transcriptome and molecular mechanism of transcription factor CabHLH118 regulating...

The bHLH family is considered as the second largest class of transcription factors in plants, playing important roles in various biological processes, particularly in color regulation. Previous research indicated that bHLH family genes were significantly involved in screening for genes associated with color variation in chili fruits. Further analysis of the predicted bHLH family genes revealed a high correlation between CabHLH118 and delphinidin, and subsequent assays showed that CabHLH118 was localized in the nucleus, possessed transcriptional activation activity, but lacked self-activation activity in yeast. Silencing or transient overexpression of CabHLH118 in pepper CS03 fruits resulted in significant phenotypic changes, accompanied by a marked decrease or increase in anthocyanin accumulation, respectively. Consistently, the expression of CabHLH118 was significantly down- or up-regulated, and the structural genes in anthocyanin biosynthesis pathway showed corresponding changes. Yeast one-hybrid (Y1H) and dual-luciferase assay demonstrated that CabHLH118 can bind to the upstream promoter of CaF3'H and promote anthocyanin formation. Furthermore, CabHLH118 may respond to blue light to enhance anthocyanin biosynthesis, although the underlying mechanism requires further verification. Collectively, these findings contribute to the understanding of anthocyanin regulation in Solanaceae plants.