VvANR silencing promotes expression of VvANS and accumulation of anthocyanin in grape berries.

Abstract

Virus-induced gene silencing (VIGS) technology was applied to silence VvANR in cv. Zaoheibao grape berries, and the effects of VvANR silencing on berries phenotype; gene expression level of ANS, LAR1, LAR2, and UFGT; enzyme activity of ANS; and accumulations of anthocyanin and flavan-3-ol were investigated. At the third day after treatment, the VvANR silenced grape berries began to turn red slightly, which was 2days earlier than that of the control group. And the flavan-3-ol content in VvANR-silenced grape berries had been remarkable within 1 to 5days, the ANR enzyme activity in VvANR-silenced grapes extremely significantly decreased in 3days, and LAR enzyme activity also decreased, but the difference was not striking. The ANS enzyme activity of the transformed berries was significantly higher than that of the control after 3days of infection, and it was exceedingly significantly higher than that of the control after 5 to 10days. The content of anthocyanin in transformed berries increased of a very marked difference within 3 to 15days. pTRV2-ANR infection resulted in an extremely significant decrease in the expression of VvANR gene, and the expression of VvLAR1, VvLAR2, VvMYBPA1, VvMYBPA2, and VvDFR were also down-regulated. However, the expression of VvANS and VvUFGT was up-regulated significantly. After VvANR silencing via VIGS, VvANR expression in grape berries was extremely significantly decreased, resulting in decreased ANR enzyme activity and flavan-3-ol content; berries turned red and deeper in advance. In addition, VvANR silencing can induce up-regulation of VvANS and VvUFGT expression, significantly increase ANS enzyme activity, and increase of anthocyanin accumulation.