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 (Pyrus × bretschneideri). 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. PbMYB120 was expressed higher in red peels than in green peels in five pear cultivars. PbMYB120 expression was positively correlated with anthocyanin accumulation. However, the transient overexpression of PbMYB120 led to the inhibition of anthocyanin accumulation and PbUFGT1 expression. Promoter binding and activation assays indicated that PbMYB120 binds to the promoter of PbUFGT1 and represses the promoter’s activity. Thus, the inhibition of anthocyanin accumulation by PbMYB120 may be correlated with the repression of PbUFGT1. Furthermore, during anthocyanin induction, the expression levels of anthocyanin activators and PbMYB120 were upregulated. This study demonstrated that PbMYB120 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.
Highlights
Coloration is an important factor of fruit quality
PbMYB120 Belongs to the FaMYB1-Like Clade of the Subgroup 4 R2R3 MYBs
The full-length coding sequence (CDS) of PbMYB120 was isolated from ‘Red Zaosu’ pear, and no variations were detected at the nucleotide level between the cloned CDS and the reference CDS from the genomic database of ‘Dangshansu’ pear
Summary
Yellow, brown, and red-skinned cultivars exist in pear. Many pigment compounds, including betalains, certain carotenoids, some terpenoids, and anthocyanins, can impart red coloration to plants [2]. Anthocyanins are the main pigments for red coloration in pear [3]. Anthocyanins confer bright red, blue, and purple coloration and have anti-oxidation, anti-radical, and anti-pathogen activities [7,8]. Anthocyanins are considered as by-products of secondary metabolism, the above functions make them important for plant survival under various environmental stress conditions [9,10]. High intake of anthocyanin-rich foods contributes to the prevention or alleviation of various diseases, including inflammations, cardiovascular diseases, neurogenic diseases, and cancers [11,12]. Many mechanisms can account for the role of anthocyanin in these diseases, for example, anthocyanin extracts can reduce viability and induce the apoptosis and differentiation of cancer cells, and activation of FK506 binding protein 52 by anthocyanins reduces the hyperphosphorylation of Tau protein aggregation and the risk of developing Alzheimer’s disease [12,13,14]
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