Abstract
Salicylic acid (SA) induces flavanol biosynthesis in grapes; however, the underlying molecular mechanisms remain largely unclear. Here, we showed that exogenous SA increases the content of flavan-3-ol, one of the main phenolics in grape leaves, by improving the activities of anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) through induction of the expression of the VvANR, VvLAR1, VvLAR2 and VvMYBPA2 genes in grape leaves. Suppression of VvANR expression in TRV-VvANR-infected grape leaves using virus-induced gene silencing (VIGS) resulted in reduced expression of the VvANR, VvLAR1, VvMYBPA1 and VvMYBPA2 genes and a subsequent reduction in the enzyme activities of ANR and LAR and the contents of (-)-epicatechin (EC) and (-)-epigallocatechin (EGC). Supplementation with exogenous SA increased the contents of flavan-3-ol monomers, i.e., (+)-catechin, (-)-epicatechin and (-)-epigallocatechin, and improved ANR activity by upregulating the expression of VvLAR1, VvLAR2, VvMYBPA1 and VvMYBPA2 in TRV-VvANR-infected grape leaves. These results collectively suggested that the application of SA may represent a useful strategy for improving flavan-3-ol biosynthesis in grapes and that ANR plays a vital role in this process.
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