The Malus crabapple transcription factor McMYB10 regulates anthocyanin biosynthesis during petal coloration

Anthocyanins are responsible for the pigmentation of flowers in the Malus crabapple, and anthocyanin accumulation is based on the expression level of both anthocyanin biosynthetic and regulatory genes. Here, we analyzed the chromatic parameters of the petals and the expression levels of anthocyanin biosynthetic pathway genes and the McMYB10 transcription factor in two cultivars with different flower colors during flower development. The results showed that the anthocyanin content and expression levels of anthocyanin-related genes in the cultivar (‘Royalty’) with red petal were much higher than those in the cultivar (‘Flame’) with a lightly pigmented petal. We also overexpressed the McCHS, McANS, and McMYB10 genes in tobacco. The transgenic plants harboring 35S :: McCHS or 35S :: McANS had an altered flower color, with the petals turned into red, compared with the control with pink petals. Moreover, plants transformed with 35S :: McMYB10 appeared to exhibit stronger anthocyanin accumulation, showing deeper red petal color compared with the McCHS- and McANS -overexpressing lines. All tested anthocyanin biosynthetic genes, especially NtDFR and NtANS, showed higher expression levels in the McMYB10 -overexpressing lines than in the control lines. These results suggested that the transcription factor McMYB10 plays an important role in anthocyanin accumulation during petal coloration in the Malus crabapple, at least partially through transcriptional regulation of its downstream genes in the anthocyanin biosynthetic pathway.