DcTT8, a bHLH transcription factor, regulates anthocyanin biosynthesis in Dendrobium candidum.

Dendrobium candidum stems are used as Chinese medicine and functional food. Red stems of D. candidum are rich in anthocyanins, which attract pollinator insects, protect the plants against environmental stress, and improve human health. The regulatory mechanisms of anthocyanin biosynthesis and stem color differentiation in D. candidum are not fully understood. Using transcriptome profiling, we identified a basic helix-loop-helix transcription factor (DcTT8) involved in anthocyanin biosynthesis in D. candidum stems. Ultraperformance liquid chromatography-tandem mass spectrometry was used to determine pigment contents and compositions in red and green stems, revealing that cyanidin is responsible for the red color. DcTT8 could bind the DcF3'H and DcUFGT promoters and finely regulate DcF3'H and DcUFGT expression. Our data indicate that DcTT8 participates in anthocyanin biosynthesis and offers novel insights into the transcriptional regulation of anthocyanin biosynthesis in D. candidum.