BoMYBL2b, an R3-MYB transcription factor, inhibits anthocyanin accumulation via directly repressing BoDFR1 gene transcription in kale.

Kale is a globally popular edible and ornamental plant with colorful inner leaves. Anthocyanin is one of the most major pigments for kale. However, the underlying regulatory mechanism for the accumulation of anthocyanin in kale has not been well understood to date. Here, we characterized an R3-MYB transcription factor, BoMYBL2b, whose mRNA was missing in the anthocyanin-rich kale inbred line, but abundant in the anthocyanin-less line. Knockdown of BoMYBL2b enhanced the anthocyanin accumulation. Y1H and DLR assays showed that BoMYBL2b directly inhibited the BoDFR1 gene expression by binding to the MRE sites on the ProBoDFR1. Besides, we found that BoMYBL2b did not interact with the bHLH proteins, indicating that the BoMYBL2b might not be part of the MBW complex. BoMYBL2b expression was significantly repressed by BoMYB1R1 under high light and cold stimulus, suggesting the possibility that BoMYB1R1-BoMYBL2b module might act as a cross-node for integrating light and temperature signals to regulate anthocyanin accumulation in kale. These findings provided a theoretical basis for molecular breeding of new kale cultivars and a reference for understanding the regulatory mechanism of anthocyanin accumulation in Brassica.