Dynamic regulation of different light intensity-modulated anthocyanin biosynthesis by BT2-TCP46-MYB1 in apple

Teosinte branched1/cycloidea/proliferating (TCP) transcription factors (TFs) play a broad role in plant growth and development. However, the role of TCP proteins in the regulation of anthocyanin biosynthesis is rarely reported. In this study, different light intensity-induced anthocyanin biosynthesis was found to be largely dependent on the functions of MdMYB1 and MdTCP46 in apple. The expression of MdTCP46 was responsive to high light intensity, and the MdTCP46 protein promoted high light intensity-induced anthocyanin biosynthesis by enhancing the binding of MdMYB1 to its target genes through direct interactions with MdMYB1. Additionally, MdTCP46 interacted with a high light responsive BTB protein, MdBT2, which ubiquitinated MdTCP46 and mediated its degradation via the 26S proteasome pathway. These results demonstrate that the dynamic regulatory module, MdBT2-MdTCP46-MdMYB1, plays a key role in different light intensity-modulated anthocyanin biosynthesis in apple, which provides new insights for future studies on the post-transcriptional regulation of TCP proteins.