PbMYB120 Negatively Regulates Anthocyanin Accumulation in Pear

Abstract

Subgroup 4 R2R3 MYBs play vital roles in the regulation of anthocyanin biosynthesis. However, there is limited knowledge regarding the functions of MYB repressors in pear (<i>Pyrus × bretschneideri</i>). Here, PbMYB120 was identified as a potential regulator of anthocyanin biosynthesis. A phylogenetic analysis revealed that PbMYB120 was clustered into the FaMYB1-like clade of the subgroup 4 R2R3 MYBs. <i>PbMYB120</i> was expressed higher in red peels than in green peels in five pear cultivars. <i>PbMYB120</i> expression was positively correlated with anthocyanin accumulation. However, the transient overexpression of <i>PbMYB120</i> led to the inhibition of anthocyanin accumulation and <i>PbUFGT1</i> expression. Promoter binding and activation assays indicated that PbMYB120 binds to the promoter of <i>PbUFGT1</i> and represses the promoter's activity. Thus, the inhibition of anthocyanin accumulation by PbMYB120 may be correlated with the repression of <i>PbUFGT1</i>. Furthermore, during anthocyanin induction, the expression levels of anthocyanin activators and <i>PbMYB120</i> were upregulated. This study demonstrated that <i>PbMYB120</i> was highly expressed in pear tissues having higher anthocyanin accumulations but acted as a repressor in the regulation of anthocyanin accumulation. PbMYB120 may work coordinately with anthocyanin activators and serve as a balancer of anthocyanin accumulation.