Anthocyanin production in grape berries enhanced by ultraviolet irradiation and its analysis of action mechanism

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Under white and UV fluorescent light, anthocyanins in Gros Colman gapes started to accumulate 48 hr after, illumination. After 72 hr, anthocyanin concentration was markedly increased by white light. Under UV lighting, a considerable amount of anthocyanins also accumulated relative to dark conditions. As white and UV light intensities increased, anthocyanins gradually increased, but promoting effect of light on anthocyanin accumulation was saturated at 60 μmol・m^<-2>・S^<-1> for white and 0.4 W・m^<-2> for UV. Using LEDs emitting specific wavelengths, the action spectrum for anthocyanin accumulation was determined. Among the visible light wavelengths, blue light largely enhanced anthocyanin accumulation, while the green to yellow range was less effective.The effects of UV-A and ABA treatments on berry coloration were compared among eight grape cultivars, the red type (Aki Queen, Ruby Okuyama, Hiro Humburg and Kaiji) and the black type (Campbell Early, Pione, Muscat Bailey A and Gros Colma … More n). In Gros Colman, Pione and Aki Quart grapes, the highest level of anthocyanin was observed in clusters treated with ABA, followed by UV-A and then controls, whereas in Hiro Humburg it was high in UV-A than ABA treatment. For Ruby Okuyama, anthocyanin level in clusters treated with ABA and UV-A was almost same. High content of anthocyanin resulted in high activity of PAL in the skin.Three cDNA clones, encoding phenylalanine ammonia-lyase were isolated from grape (Vitis labruscana, cv Pione) skin by RT-PCR and RACE-PCR methods. A strong expression of the three genes and a high PAL activity was detected at early stage of fruit growth, followed by a reduction of the expression and activity to trace level at veraison. While in white type cultivars such as Muscat of Alexandria gene expression and enzyme activity remained at trace level during fruit ripening, in black type cultivar such as Pione and Gros Colman the increase in gene expression and enzyme activity during ripening stage were observed, correlating with anthecyanin synthesis. The increase in gene expression and enzyme activity were dramatically stimulated by ABA treatment at veraison. Less