Molecular mechanism of pear R2R3-MYB transcription factor PbMYB30 that dynamically regulates anthocyanin synthesis

Anthocyanin, a pivotal metabolite governing red pigmentation in plant organs, is predominantly regulated by R2R3-MYB transcription factors. Leveraging 'Red zaosu', a spontaneous red-pericarp mutant originating from white pear, combined with phytohormone treatments (MeJA/ABA), this study elucidates the molecular mechanism whereby PbMYB30 orchestrates dynamic anthocyanin biosynthesis. Results indicate that PbMYB30, localized in the nucleus, transcriptionally activates anthocyanin accumulation via direct binding to the promoters of PbDFR and PbUFGT; however, formation of the MYB-bHLH-WD40(MBW) ternary complex with PbbHLH33 and PbWD40 substantially attenuates its transcriptional activation capacity. Protein-protein interactions within this complex were validated by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays, and MBW ternary complex repressive role was confirmed via transient co-expression. Furthermore, exogenously applied MeJA and ABA enhanced anthocyanin synthesis by inducing PbMYB30 promoter activity. This work provides the first evidence of MBW complex-mediated functional repression of MYB in pear, establishing a molecular framework for targeted breeding of red-skinned pear cultivars.