Mapping and functional characterization of the golden fruit 1 (gf1) in melon (Cucumis melo L.).

Abstract

Key message: A missense mutation that causes premature termination of the CmEGY1 protein leads to golden fruit in melon. Melon (Cucumis melo L.) is an economically important fruit crop that has been cultivated for thousands of years. Fruit color, a crucial trait influencing the appearance quality and economic value of melons, is primarily determined mainly by the type and concentration of pigments such as chlorophyll, carotenoids, and flavonoids. Identifying the genetic loci that govern melon fruit color contributes to breeding efforts aimed at enhancing melon rind coloration. This study reports an EMS-induced mutant, designated as gf1 (golden fruit 1), which produces fruit with both golden peel and flesh. Through MutMap and map-based cloning, we localized the gf1 locus to an 862 kb region containing 42 SNPs. Of these, a single SNP in the coding region caused a stop-gained mutation in the gene Cme13C08g017690, which exhibits the highest sequence similarity to Arabidopsis ETHYLENE-DEPENDENT GRAVITROPISM-DEFICIENT AND YELLOW-GREEN 1 (EGY1). Genome editing of CsEGY1, the cucumber homolog, confirmed its role in golden-fruit formation. Transcriptome and metabolome analyses revealed reduced flavonoid and carotenoid contents, accompanied by the downregulation of related biosynthetic genes. The identification and characterization of egy1 provide novel genetic insights and a valuable resource for improving melon appearance through breeding.