Identification of the Regulatory Genes of UV-B-Induced Anthocyanin Biosynthesis in Pepper Fruit

Fruit peels of certain pepper (Capsicum annum L.) varieties accumulate a large amount of anthocyanins and exhibit purple color under medium-wave ultraviolet (UV-B) conditions, which severely impacts the commodity value of peppers. However, the regulatory mechanism of the above process has not been well studied so far. To explore which key genes are involved in this regulatory mechanism, pepper variety 19Q6100, the fruit peels of which turn purple under UV-B conditions, was investigated in this study. Transcription factors with expression levels significantly impacted by UV-B were identified by RNA-seq. Those genes may be involved in the regulation of UV-B-induced anthocyanin biosynthesis. Yeast one-hybrid results revealed that seven transcription factors, CabHLH143, CaMYB113, CabHLH137, CaMYBG, CaWRKY41, CaWRKY44 and CaWRKY53 directly bound to the putative promotor regions of the structural genes in the anthocyanin biosynthesis pathway. CaMYB113 was found to interact with CabHLH143 and CaHY5 by yeast two-hybrid assay, and those three genes may participate collaboratively in UV-B-induced anthocyanin biosynthesis in pepper fruit. Virus-induced gene silencing (VIGS) indicated that fruit peels of CaMYB113-silenced plants were unable to turn purple under UV-B conditions. These findings could deepen our understanding of UV-B-induced anthocyanin biosynthesis in pepper.