Ectopic expression of grape hyacinth R3 MYB repressor MaMYBx affects anthocyanin and proanthocyanidin biosynthesis and epidermal cell differentiation in Arabidopsis
Wang, Jiangyu | Zhang, Boxiao | Tian, Shuting | Zhang, Han | Gong, Jiaxin | Chen, Kaili | Du, Lingjuan
Single-repeat R3 MYB transcription factors regulate multiple developmental and metabolic pathways in plants. The anthocyanin-related R3 MYB repressor MaMYBx was previously identified in grape hyacinth (Muscari spp.), and its ectopic expression reduced the accumulation of anthocyanin in tobacco petals. However, whether the function of MaMYBx is conserved across plant species remains unclear. Here, we report that ectopic expression of MaMYBx regulates anthocyanin and proanthocyanidin (PA) biosynthesis and epidermal cell differentiation in Arabidopsis. MaMYBx overexpression in Arabidopsis decreased the accumulation of anthocyanin and PA by downregulating the late structural genes (AtDFR, AtANS, AtANR, and AtGST), some key regulatory factors of MBW complexes (AtPAP1, AtTT8, and AtGL3) and an R3 MYB gene (AtCPC) involved in flavonoid biosynthesis. In addition, MaMYBx also modulated trichome formation and root hair differentiation by downregulating MBW component genes (AtGL1, AtWER, and AtGL3) and their target gene AtGL2 and by upregulating several R3 MYB genes (AtTRY and AtTCL1). We further found that MaMYBx transgenic plants accumulated less anthocyanin than did wild-type plants under salt, osmotic pressure, cold, and nitrogen stresses. Moreover, the effect was even greater, and significantly less anthocyanin accumulated. In conclusion, these results implied functional conservation of MaMYBx in anthocyanin and PA biosynthesis pathways of Arabidopsis. Therefore, MaMYBx likely represents a new potential gene for the molecular breeding of horticulture and ornamental plants via the regulation of anthocyanin and PA.
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