A novel bHLH transcription factor, FabHLH110, is involved in regulation of anthocyanin synthesis in petals of pink-flowered strawberry.

The pink-flowered strawberry is a kind of perennial herb that serves as both an ornamental plant with a range of red-colored petals and a food crop, which was produced by distant hybridization of Fragaria × Potentilla. Although there have been numerous reports on anthocyanin synthesis in strawberry fruits, the mechanism by which bHLH transcription factors regulate anthocyanin synthesis in strawberry red petals remains unclear. In this study, a total of 376 FabHLHs were finally identified, which were divided into 25 subfamilies. According to transcriptome sequencing, phylogenetic tree construction, correlation analysis and real-time fluorescence quantitative analysis, the differential gene FabHLH110 was screened out to regulate the synthesis of flower petal anthocyanin of pink-flowered strawberry. Specifically, transient overexpression of FabHLH110 in petals of pink-flowered strawberry increased anthocyanin accumulation, while virus-induced FabHLH110 gene silencing had the opposite effect, indicating FabHLH110 functioned as a positive regulator of anthocyanin biosynthesis. In addition, it was found that FabHLH110 could not bind to the promoter of FaDFR, FaANS, FaUGT and FaGST, which should interact with FaMYB10, FaMYB90 and FaMYB114 to form MBW complex to promote anthocyanin accumulation in fruit and petals of pink-flowered strawberry, respectively. Our findings provide new insight into the regulatory network of anthocyanin synthesis in petal of pink-flowered strawberry and a new strategy for breeding rich anthocyanin.