The PuERF27-PuMYB10-PuGSTF12 Module Regulates Melatonin-Induced Anthocyanin Biosynthesis in Pear Fruits

Anthocyanins, flavonoids with strong antioxidant activity, give rise to a fruit peel color and provide health benefits. Studies have revealed that melatonin promotes anthocyanin accumulation. However, the function of endogenous hormones in this process remains elusive. Here, we investigated the effect of ethylene signaling on anthocyanin accumulation in melatonin-treated pear fruit. Melatonin promoted anthocyanin accumulation while repressing ethylene production; its effect on anthocyanin biosynthesis in the background of ethephon pretreatment was eliminated. Transcriptome analysis revealed PuERF27, a melatonin-induced ethylene response factor (ERF), as a candidate gene. Transient overexpression of PuERF27 is essential for enhancing anthocyanin accumulation and activating anthocyanin biosynthesis genes, whereas PuERF27 silencing repressed melatonin-induced anthocyanin accumulation. Yeast one-hybrid, electrophoretic mobility shift, and GUS assays indicated that PuERF27 could bind directly to and positively regulate the PuMYB10 and PuGSTF12 promoters. Further studies revealed that PuERF27, together with PuMYB10, synergistically transactivates the PuGSTF12 promoter. These results indicate that melatonin-induced PuERF27 may directly promote PuGSTF12 expression and indirectly activate structural genes through PuMYB10, thereby leading to the biosynthesis and transport of anthocyanins.