Three types of ultraviolet irradiation differentially promote expression of shikimate pathway genes and production of anthocyanins in grape berries.

Modulation of flavonoid biosynthesis in grape berries has always aroused great attention among researchers. However, little study has been made on the shikimate pathway that guides photo-assimilate flow into flavonoid metabolism. The present study indicated that the treatments of three ultraviolet (UV) wavelengths differentially up-regulated transcriptional expression of some structural genes in the shikimate pathway and post-chorismate pathway of grape berries and this up-regulation was developmental stage-dependent and not synchronous. Of these genes, VvDAHPS-1 and VvDAHPS-2 encoding the entry enzymes of the shikimate pathway showed most significant UV-response and their transcription was strongly promoted by UV-A stimuli in the 3-week grapes and by UV-B and UV-C in the 7-week and 11-week grapes. The elevation of VvAS expression by UV induction appeared in the 3-week grapes and VvCM-1 was expressed relatively more concomitantly with berry mature. Correspondently, UV-B and UV-C irradiation increased the content of various anthocyanins in the 11-week grapes, but UV-A did not. These data suggest that UV-responsive production of anthocyanins is in part a consequence of the increase in carbon supply via promoting the shikimate pathway and the Phe/Trp specific pathway.