Transcriptional Activation of Anthocyanin Biosynthesis in Developing Fruit of Blueberries ( Vaccinium corymbosum L.) by Preharvest and Postharvest UV Irradiation

The effect and mechanism of preharvest and postharvest ultraviolet (UV) irradiation on anthocyanin biosynthesis during blueberry development were investigated. The results showed that preharvest UV-B,C and postharvest UV-A,B,C irradiation significantly promoted anthocyanin biosynthesis and the transcripts of late biosynthetic genes (LBG) VcDFR, VcANS, VcUFGT, and VcMYB transcription factor as well as DFR and UFGT activities in anthocyanin pathway in a UV wavelength- and developmental stage-dependent manner. VcMYB expression was positively correlated with that of VcANS and VcUFGT and coincided with anthocyanin biosynthesis responding to the UV radiation. Sugar decreased during postharvest but increased during preharvest UV radiation in mature fruit. Our results indicate that UV-responsive production of anthocyanins is mainly caused by the activation of anthocyanin downstream pathway genes, which could be upregulated by VcMYB. Furthermore, different potential response mechanisms may exist between preharvest and postharvest UV radiation in blueberries, involving a systemic response in living plants and a nonsystemic response in postharvest fruit.