Light-responsive PyNAC90 orchestrates anthocyanin biosynthesis through combinatorial transcriptional activation and COP1-mediated degradation in pear

Abstract Anthocyanins confer diverse biological activities and health benefits, and represent a key quality trait in fruit. In pear, red skin coloration arises from anthocyanin accumulation, a process strongly induced by light. Here, transcriptomic analyses identified PyNAC90 as a candidate regulator promoting anthocyanin biosynthesis. The expression level of PyNAC90 gradually increased with extended bag removal. Stable transformation in pear callus and transient overexpression in pear skin showed that PyNAC90 overexpression significantly enhanced anthocyanin accumulation, whereas PyNAC90 silencing significantly suppressed anthocyanin biosynthesis. Dual-luciferase reporter assays demonstrated that PyHY5 directly induced PyNAC90 , while PyNAC90 directly activated PyMYB10 and indirectly activated the downstream structural genes PyDFR and PyANS . Furthermore, co-expression of PyNAC90, PyMYB10, and PybHLH3 synergistically activated the downstream structural genes PyDFR and PyANS . Moreover, Y2H, LCI, and BiFC assays confirmed that PyNAC90 physically interacted with PyMYB10, strengthening cooperative transcriptional regulation of anthocyanin biosynthesis. The E3 ubiquitin ligase PyCOP1 also interacted with PyNAC90 both in vivo and in vitro, mediating its degradation, thereby reducing anthocyanin accumulation. Collectively, our results elucidate a molecular mechanism by which light-responsive NAC transcription factors regulate anthocyanin biosynthesis and expand the regulatory network underlying light–induced pigmentation.