McMYB10 Modulates the Expression of a Ubiquitin Ligase, McCOP1 During Leaf Coloration in Crabapple.

In higher plants, anthocyanins are protective secondary metabolites, which contribute to the color of leaves, stems, flowers, and fruits, and have been found to have an antioxidant role in human health. In this study, we determined the expression of and its specific E3 ubiquitin ligase, McCOP1, in crabapple leaves during the course of a day and in five leaf development stages. Interestingly, the results showed that the transcription level of genes was higher in daylight than at night, and the transcripts of presented a positive correlation with the transcription of and and anthocyanin accumulation in a crabapple cultivar with red-colored leaves. Several MYB transcription factor (TF) binding sites of the MYBCORE type were found in the and promoters, and we deduced that there may be a relationship between and and at the transcriptional level. Yeast one hybrid (Y1H) and electrophoretic mobility shift assays (EMSA) demonstrated that the TF binds specifically to the promoter of and . Furthermore, increased levels of McMYB10 promoted anthocyanin biosynthesis and the expression level of and in crabapple leaves during continuous light treatments, and overexpression or silencing of in crabapple leaves and apple fruits also result in an increase or decrease, respectively, in the expression of and and in anthocyanin biosynthesis. Our results reveal a new self-regulation mechanism in where modulates its own expression by activating and expression to promote ubiquitination of the McMYB10 protein by McCOP1.