Ethylene-activated PpERF105 induces the expression of the repressor-type R2R3-MYB gene PpMYB140 to inhibit anthocyanin biosynthesis in red pear fruit.

Abstract

Ethylene induces anthocyanin biosynthesis in most fruits, including apple (Malus domestica), strawberry (Fragaria × ananassa), and plum (Prunus spp.). However, ethylene inhibits anthocyanin biosynthesis in pear (Pyrus spp.), but the underlying molecular mechanism has not been characterized. In this study, ethylene induced the expression of PpERF105, which encodes a transcription factor. PpERF105 functioned as a transcriptional activator, but it inhibited anthocyanin biosynthesis in pear. A transcriptome analysis revealed that PpERF105 activated the expression of PpMYB140, which encodes an R2R3-MYB transcriptional repressor. Moreover, PpMYB140 directly inhibited the expression of anthocyanin-related structural genes. It also competed with PpMYB114 for the binding to bHLH3, ultimately resulting in the formation of the MYB140-bHLH-WDR complex rather than the conventional MBW complex, thereby further inhibiting anthocyanin biosynthesis. Furthermore, PpMYB140 prevented the overaccumulation of anthocyanins in the absence of ethylene. Collectively, our study data indicate that ethylene-induced PpERF105 inhibits anthocyanin biosynthesis by upregulating PpMYB140 expression. Our findings may be useful for elucidating the molecular basis of the ethylene-mediated inhibition of anthocyanin biosynthesis in fruit.