The E3 ubiquitin ligase COP1 inhibits sugar and anthocyanin accumulation in strawberry fruit

Abstract Light strongly affects strawberry fruit quality. The ubiquitin E3 ligase CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) negatively regulates light signaling. However, its role in fruit quality remains unclear. This study demonstrate that FvCOP1 plays a negative role in strawberry fruit quality. Here, we generated fvcop1 knockout mutants in diploid strawberry (Fragaria vesca). The mutants showed substantially changes in fruit color and shape. Metabolomic analyses revealed elevated levels of sugars, anthocyanins, vitamins, lignin, flavonoids, and phenolic acids in fvcop1 mutants compared to wild type. Transcriptome analysis identified key genes in sugar, anthocyanin, flavonoid, and lignin biosynthesis pathways. Moreover FvCOP1 suppresses the accumulation of sugars, anthocyanins and flavonoids by inhibiting transcriptional activation of downstream genes regulated by FvHY5, FvRIF and FvMYB10. We demonstrated that FvHY5 and FvRIF directly bind to promoters of sugar/anthocyanin biosynthesis genes to activate their expression. Furthermore, FvCOP1 ubiquitinates FvHY5, FvMYB10, and FvRIF, leading to their destabilization and thereby repressing sugar and anthocyanin production.. These findings establish FvCOP1 as a molecular brake on light-mediated fruit quality improvement. Targeting FvCOP1 in breeding programs could enhance strawberry nutritional and commercial value by optimizing light-responsive metabolite accumulation.