FveMYB1-FveTPR2-FveHDA6 complex prevents anthocyanin overaccumulation during strawberry fruit ripening

Abstract

Anthocyanins serve as critical secondary metabolites in plants. However, the molecular mechanisms underlying plant regulation to prevent anthocyanin overaccumulation remain largely elusive. This study reveals that both transcript and protein levels of the anthocyanin repressor FveMYB1 in woodland strawberry progressively increase during fruit development, peaking at the ripening stage. Stable transformation confirmed that FveMYB1 suppressed anthocyanin biosynthesis. To investigate how FveMYB1 suppresses anthocyanin biosynthesis, we performed yeast two-hybrid screening of a strawberry fruit cDNA library using FveMYB1 as bait. FveMYB1 was found to interact with two types of regulators: the transcriptional co-repressor FveTPR2 and histone deacetylases FveHDA6, respectively. Both FveTPR2 and FveHDA6 exhibited the highest expression levels in ripening fruits, and these genes were found to repress anthocyanin biosynthesis during fruit maturation. Interestingly, three members (FveMYB1, FveTPR2 and FveHDA6) interact with each other to form a ternary complex to repress anthocyanin biosynthesis. Furthermore, TSA treatment and Chip-qPCR demonstrated that FveMYB1-FveTPR2-FveHDA6 complex mediate histone deacetylation at key anthocyanin biosynthetic genes (FveF3H, FveCHS, and FveANS). This epigenetic modification represses the expression of these genes, ultimately reducing anthocyanin accumulation to prevent overproduction in strawberry fruits and this regulatory mechanism is conserved in various plants. These findings elucidate a novel regulatory pathway that fine-tunes anthocyanin biosynthesis during fruit ripening.