CmSN Regulates Fruit Skin Netting Formation in Melon

Melon (Cucumis melo) includes more than ten botanical groups, many of which feature netting ornamentation on the surface of mature fruit. Ripe melons display a netted skin that signifies their ripeness and readiness for consumption. Previously, we identified SKIN NETTING (CmSN), which encodes an EamA-like transporter family protein, as the candidate gene controlling fruit skin netting formation in melon, while its biological functions remain unclear. In this study, we demonstrated that the expression of the CmSN gene was considerably lower in netted melons compared to smooth-skinned melons, indicating a negative correlation between CmSN expression and netting formation. Subsequently, we employed transient overexpression and virus-induced gene silencing (VIGS) experiments to explore the role of CmSN gene during fruit development. Overexpression of the CmSN gene inhibited netting development, whereas silencing it promoted netting formation. Using heterologous transformation in tomato, we further confirmed the effect of the CmSN gene on rind texture and toughness, as these tomatoes exhibited rougher and tougher skins. Analysis with near-isogenic lines (NILs) revealed that CmSN gene-bearing fruits (NIL_CmSN) possessed significantly harder rinds than the control smooth-skinned variety HB42, underscoring the role of CmSN in enhancing rind protection. Together, our research offers essential insights into the netting formation and genetic improvement of melon fruits.