Novel_miR_130 Targeting VvCHX20 in Grape Ion/Water Transport and Fruit Growth

Gibberellic acid (GA 3 ) is vital for regulating fruit development, while the mechanisms underlying its modulation of water and ion transport remain unclear. This study explored the effects of exogenous GA 3 (40 mg/L, T1; 70 mg/L, T2) on ‘Red Globe’ grapes ( Vitis vinifera L.), focusing on the role of novel_miR_130 and its target gene VvCHX20 —a cation/H + antiporter. Compared to the control (CK), GA 3 treatment significantly increased individual fruit weight and total soluble solids (TSS) content, with T2 exhibiting the most pronounced enhancements. Furthermore, GA 3 modified fruit water status throughout development by elevating free water content, total water content, real-time water potential, 24-hour saturated water potential, osmotic potential, and turgor pressure, while decreasing bound water content. Transcriptomic analysis revealed 12 miRNAs that regulate 11 mRNAs associated with water and ion transport. Notably, GA 3 downregulated novel_miR_130 and upregulated VvCHX20 , indicating negative regulation. VvCHX20 encodes a plasma membrane-localized cation/H + antiporter featuring 10 transmembrane domains. Overexpression of VvCHX20 in tomato increased fruit size (weight and transverse diameter), free water and TSS contents, and specifically elevated K + levels. Cross-sectional showed that more locules and thicker pericarps. Through Y1H and dual-luciferase reporter assays, we further identified four transcription factors—VvAAR3, VvPUB23, VvDPMS1, and VvNH18—that bind to and activate the VvCHX20 promoter, suggesting their roles as upstream regulators in the GA 3 -responsive pathway. In summary, GA 3 downregulates novel_miR_130 to relieve its repression of VvCHX20 and promotes transcriptional activation of VvCHX20 through specific TFs, thereby promoting K + transport and optimizing fruit water status, ultimately enhancing fruit growth and quality.