ROS scavenger Hypotaurine delays postharvest softening of ‘Kyoho’ grape by regulating pectin and cell metabolism pathway

The rapid softening of postharvest fruit has a serious detrimental effect on quality and market value. In this study, postharvest grape berries treated with hypotaurine (HT) or H2O2 were employed to explore the dynamic physical and transcriptional changes after the treatment. The berry firmness and the content of propectin were higher in the berries with HT treatment compared to the control (CK) and H2O2 treatment. A total of 1774 differentially expressed genes (DEGs) were identified from comparisons of CK_vs_HT (1,020) and CK_vs_H2O2 (1,072). Weighted gene coexpression network analysis (WGCNA) showed that genes assigned to ‘MEgreen’ were predicted to be highly correlated to fruit firmness and propectin content. Based on transcriptome and quantitative real-time polymerase chain reaction (RT-qPCR), expression levels of VvMYB-like, VvNAC22, VvPEI and VvCESA-like were upregulated whereas VvMADS-box and VvPG were downregulated in HT-treated berries compared to H2O2 treatment. Dual luciferase reporter assay confirmed that VvMYB-like and VvNAC22 upregulate the expression of VvPEI and VvCESA respectively by binding to the corresponding sites of their promoters. Meanwhile, HT treatment triggered the differential expression of Accelerated Cell Death 6 (VvACD6), VvXyloglucan galactosyltransferase (VvXyG galactosyltransferase) and Cell wall/Vacuolar Inhibitor of Fructosidase 1-like (VvC/VIF1-like). Finally, a possible regulatory model that HT delays berry softening by regulating pectin and cell metabolism pathway through VvMYB-like and VvNAC22 was proposed. This study laid a foundation for understanding the molecular mechanisms of delaying berry softening which HT mediated.