VcBBX, VcMYB21, and VcR2R3MYB Transcription Factors Are Involved in UV–B-Induced Anthocyanin Biosynthesis in the Peel of Harvested Blueberry Fruit

This study was carried out to better understand the mechanism responsible for increasing the anthocyanins in blueberries after UV–B radiation at 6.0 kJ m–2 for 20 min. UV–B induced upregulation of genes involved in anthocyanin biosynthesis in blueberry fruit compared to a nontreated control. Phenylalanine ammonia lyase, chalcone synthase, and flavanone 3′-hydroxylase, which are enzymes that function upstream of anthocyanin biosynthesis, were significantly expressed by UV–B. Expression levels of VcBBX, VcMYB21, and VcR2R3MYB transcription factors (TFs) were upregulated by UV–B in the same manner as the anthocyanin biosynthesis genes. The significant increase in the expression of TFs occurred immediately after UV–B treatment and was then maximized within 3 h. In accordance with these changes, individual anthocyanin contents in the fruits treated with UV–B significantly increased within 6 h and were 2–3-fold higher than the control. Our results indicated that UV–B radiation stimulates an increase in anthocyanin biosynthesis, which could be upregulated by the TFs studied.