Critical role of TCP7 in mediating RBH-induced fungal resistance in postharvest grape berries

(R)-β-homoserine (RBH) is a structural analogue of β-aminobutyric acid (BABA) that can enhance plant resistance to a wide range of pathogens. Here, we investigated the regulatory role of VvTCP7 on the RBH-induced priming response against Botrytis cinerea in grapes. The results showed that RBH primed a defense mechanism in grape berries and enhanced their response to fungal infection. RBH upregulated the expression of a group of genes involved in SA synthesis, thus inducing SA accumulation in grapes. VvTCP7 has high homology to AtCHE in Arabidopsis thaliana and is recognized to be a nucleus-localized protein that promotes SA synthesis. Notably, RBH elevated VvTCP7 expression in harvested grape berries, which was accompanied by enhanced expression of VvNPR1, a master regulator of SAR, as well as the SA-responsive PR genes. Additionally, Y1H, EMSA and DLR assays confirmed that VvTCP7 has the ability to bind directly to the GGNCCC motif within the VvICS promoter to induce VvICS transcription and SA synthesis. Overexpression of VvTCP7 in Arabidopsis led to a marked increase in the transcription of PR genes, enhancing defensive response to B. cinerea. However, the VvTCP7 knockout led to a decrease in PR gene expression and increased susceptibility to the fungus. Collectively, the data suggest that VvTCP7 contributes to RBH-induced SAR priming by activating the SA synthesis and resultant enhances SAR defenses to combat fungal invasion.