PmHY5-PmMYB113-mediated anthocyanins biosynthesis underlies flower color variation in industrially important woody ornamental Prunus mume

Abstract

Prunus mume (Japanese apricot) is an important ornamental woody plant cultivated for over 3000 years particularly in China and East Asia. Its flowers not only have horticultural value but are also rich in flavonoids such as anthocyanins, used in medicine and skincare products by cosmetic industry. Anthocyanins are abundantly found in red flowers of P.mume which is uncommon compare to pink and white flower phenotypes. Molecular breeding efforts are useful in identifying genetic factors regulating anthocyanins biosynthesis to increase the production of anthocyanins in flowers. However, the molecular mechanism of anthocyanins biosynthesis in P.mume is largely remains unclear. In this study, through transcriptome and metabolite analysis of three different flower phenotypes of P.mume, we identified group of genes, including two structural genes of flavonoids biosynthesis pathway ( PmDFR and PmFLS ) a light responsive master regulator of anthocyanins biosynthesis PmHY5, anthocyanins repressor PmCOP1 and a MYB family transcription PmMYB113 . Expression patterns of these genes correlated with changing anthocyanins content in flower of P. mume . Further investigation revealed that PmHY5 acts as a master switch that activates PmMYB113 in the cell nucleus to trigger anthocyanins biosynthesis by down-regulating flavonols biosynthesis gene PmFLS1 and up-regulating PmDFR a key gene of anthocyanins pathway. In contrast PmCOP1 negatively regulates this process in response to the absence of light through the degradation of PmHY5 proteins in nucleus which results in the suppression of anthocyanins accumulation. Over-expression of PmMYB113 in Nicotiana tabacum resulted in the up-regulation of NtDFR and accumulation of significantly higher anthocyanins content in the flowers hence paving the ways for future breeding of desire color phenotypes with high anthocyanins content beneficial for both cosmetic, aesthetic and medicinal use.