Regulation Mechanism Of Light Intensity On Anthocyanin Biosynthesis In Apple Peel

Anthocyanin is a kind of plant pigment, plays an important role in apple fruits pigmentation. The biosynthesis of anthocyanin is regulated by the environmental factor-light.In order to clarify the regulation mechanism of light intensity on anthocyanin biosynthesis,the present study took bag removed ‘Fuji’ and ‘Red Delicious’ apple peels as plant materials,analysed 14 kinds of phenolic compounds concentrations at different light intensity in these two cultivars and anthocyanin biosynthesis key enzyme activities, structure gene and trancription factor gene expressions in ‘Fuji’ apple peel. The study gained the anthocyanin biosynthesis response curve to light intensity and major results are shown below:1. Anthocyanin biosynthesis in ‘Fuji’ and ‘Red Delicious’ apple peels showed an ‘S’curve as light intensity increase and there are 3 stages in this curve: slowly rising stage, rapid linear growth stage and plateau stage. Concentrations of flavonols such as quercetin-3-galactoside, quercetin-3-rutinoside and quercetin-3-glucoside also showed significant ‘S’curve as the increasing of light intensity. The concentration of quercetin-3-arabinoside showed significant decrease at 100% light intensity treatment compared with 90% light intensity treatment. In ‘Fuji’ apple peel, contents of chlorogenic acid showed a slowly increase as light intensity increases. Other phenolic compounds like gallic acid, phloridzin,flavanols, quercetin-3-xyloside and quercetin-3-rhamnoside did not show significant response to light intensity;2. The mechanism of anthocyanin biosynthesis was varied at different light intensity in apple fruit peels. Althrough 7 anthocyanin biosynthesis gene expressions(Md MYB10, Md HY5,Md PAL, Md CHS, Md DFR, Md ANS and Md UFGT) showed significant correlation to anthocyanin concentration, only ANS and UFGT activities showed significant correlation to anthocyanin contents at different light intensity treatments. This means ANS and UFGT play very important role in anthocyanin biosynthesis. In the rapid linear growth stage of ‘S’ curve,only ANS activity showed significant correlation to anthocyanin concentration. It concludes that ANS activity is the only limiting factor to anthocyanin biosynthesis during this stage.