Virus-induced silencing of MYB and WD40 transcription factor genes affects the accumulation of anthocyanins in chilli pepper fruit

The MYB, MYC, and WD40 transcription factors (TFs) are known to regulate the expression of structural biosynthetic genes at different steps depending on the plant species. In this work, we used an agroinfiltration protocol with Tobacco rattle virus (TRV) constructs containing partial sequences from MYB or WD40 for virus-induced gene silencing (VIGS) to demonstrate their participation in the regulation of anthocyanin biosynthesis in chilli pepper (Capsicum eximium) fruits. The accumulation of anthocyanins in chilli pepper fruits of plants transformed with TRV2-MYB and TRV2-WD40 constructs was significantly reduced compared to the control or empty TRV2-transformed plants. A significant reduction in gene expression of both TFs was also detected. The expressions of the chalcone synthase (CHS), chalcone isomerase (CHI), flavonoid 3',5'-hydroxylase (F3'5'H), dihydroflavonol 4-reductase (DFR), and UDP-glucose:flavonoid 3-O-glucosyltransferase (3GT) genes were decreased in the plants transformed with the TRV2-MYB construct but not the transcription of flavanone 3-hydroxylase (F3H). When chilli pepper plants were infected with the TRV2-WD40 construct, a significant reduction in CHS, F3H, F3'5'H, DFR and 3GT expression, but not in CHI in the fruits was observed.