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 (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.

Role of core structural genes for flavonoid biosynthesis and transcriptional factors in flower color of plants

“…It is responsible for encoding regulatory factors and controlling the transcription and activity of multiple enzymes in biosynthesis pathways. MYB [88][89][90], bhLh [91] and WDR [92] are several major transcription factors that adjust anthocyanin synthesis. MYB or MYB-bhLh-WDR complexes (MBW) are combined onto the promoter of structural genes to regulate downstream genes [1].…”

MrMYB6 From Chinese Bayberry (Myrica rubra) Negatively Regulates Anthocyanin and Proanthocyanidin Accumulation

“…It must be pointed out that without any partners, MrMYB6 displayed no suppression on the promoters of either MrANS or MrUFGT in anthocyanin-specific pathway (Figure 3C). On the contrary, researches have revealed that several R2R3-MYB repressors such as VcMYBC2, PbMYB120, MaMYB4, and FaMYB1 on their own were sufficient to inhibit anthocyanin accumulation in many fruits such as blueberry, pear, banana, and strawberry (Aharoni et al, 2001;Song et al, 2020;Deng et al, 2021;Li et al, 2021). Therefore, we supposed that there might be other MYB TFs independently down-regulating anthocyanin accumulation in bayberries, which deserved further studies.…”

Recent Advanced Metabolic and Genetic Engineering of Phenylpropanoid Biosynthetic Pathways

“…In Arabidopsis, AtMYB32 and AtMYB4 knockout mutant enhanced the yield of lignin and sinapate esters by increasing the expression level of the C4H gene. In addition, MYB4 acts as a repressor of phenylpropanoid metabolisms by downregulating the expression of genes encoding arogenate Dehydratase 6, which cat-alyzes the final step in phenylalanine biosynthesis [132,145]. MdMYB6 isolated from apple, reduced the anthocyanin accumulation upon its overexpression in Arabidopsis thaliana.…”