Response Of Kaempferol Glycosides And Sinapate Esters In Arabidopsis Thaliana To UV-B Radiation

In the present study, Arabidopsis thaliana, a model plant widely used in molecular genetic, and developmental biology, was continously grown under UV-B radiation (40μw·cm-2) for7days. Here we report the effect of UV-B radiation on kaempferol glycosides and sinapate esters content in rosette leaves of Arabidopsis thaliana.After UV-B radiation for7days, the chlorophyll a/b value significantly lower than the control in young seedlings. The chlorophyll a/b value decreased significantly with UV-B treatment in one day, the value has recovered to former level after the light and dark recovery. UV-B radiation treatment resulted in the decrease of the water content, especially the mature plants. The water content had no significantly change with UV-B treatment in one day. The results show that the chosen UV-B radiation intensity had no serious damage on Arabidopsis thaliana.The results suggested that the contents of three kaempferol glycosides in young seedlings haven certain accumulation after UV-B radiation for7days. While that in the mature seedlings is shown only on the instantaneous response of UV-B radiation. Corresponding to increased content of three kaempferol glycosides, the kaempferol glycosides biosynthesis genes chs and fls1showed increased expression in both young and mature plants, and the response of expression level about kaempferol-3-O-rhamnosyl glucoside-7-O-rhamnoside was significantly higher than that in kaempferol-3-O-glucoside-7-O-rhamnoside and kaempferol-3-O-rhamnoside-7-O-rhamnoside. In addition, the content of kaempferol glycosides in young seedlings is higer that in that in mature seedlings, but the responsiveness of kaempferol glycosides in young seedlings far lower than that of mature seedlings.The sinapate esters in rosette leaves of Arabidopsis thaliana.were accumulated in response to7day UV-B exposure. The proportion of sinapoylglucose decreased with UV-B treatment in one day, while the content of sinapoylmalate which is its downstream products showed a significant increase. Corresponding to the changes of two sinapate esters contents, fahl and sngl which are the key genes of sinapate esters biosynthesis changed. In the composition of two sinapate esters components, sinapoylmalate content is far higher than sinapoylglucose, the differences are about10times more.In addition, the sinapate esters content in young seedlings is higer that in that in mature seedlings, but but the responsiveness of sinapate esters in young seedlings far lower than that of mature seedlings. It is similar to responsiveness of kaempferol glycosides. These results indicate that kaempferol glycosides and sinapate esters are effective UV-B protectants, which exhibit constitutive defense response in young plants and inducible defense response in mature plants.