The Synthesis Of Anthocyanins And Expression Of Related Genes On’ Granny Smith’ Apples After Bag Removal

‘Granny Smith’ is one of the traditional cultivars in the world and also the typical greencultivar. While in the Loess Plateau region of China, it was discovered that ‘Granny Smith’could rapidly turn red following bag removal. This could be an important experimentalmaterial for the research of apple coloring mechanism. The experiments were carried out atBaishui Apple Experimental Station of Northwest A&F University which is located in theLoess Plateau region of China during2011-2012years. In order to clarify the reason for thecolor formation of this cultivar, fruit color, the contents of chlorophylls, carotenoids,anthocyanins, phenolic compounds were analysed in the coloring process of ‘Granny Smith’apples. The expression of anthocyanin biosynthetic and regulatory genes was also deteted.The results are as follows:1. After bag removal, the values of L*, b*and h*from Day0to Day16decreasedgradually, while the value of a*increased sharply, which indicated bagging treatment couldpromote red color formation on ‘Granny Smith’ apples.2. After bag removal, the skin of ‘Granny Smith’ apples contained only two types ofanthocyanins, cyanidin3-O-galactoside and cyanidin3-O-arabinoside. Cyanidin3-O-galacto-side accounted for most of the total anthocyanin contents and accumulated within13days,and finally reached the maximum level of0.122mg/g DW at Day13. While no anthocyaninwas detected in the non-bagged apples. In the meanwhile, the concentrations of chlorophyllsand carotenoids in the skin of ‘Granny Smith’ apples treated with bagging were significantlydecreased.3. After bag removal, the contents of catechin, procyanidin B2, quercetin3-galactoside,chlorogenic acid, caffeic acid and phloridzin decreased obviously as compared to the controlgroup. In reverse, the concentration of epicatechin increased.4. After bag removal, the expression levels of MdF3H, MdDFR, MdANS and MdUFGTwere increasing gradually, especially the transcription of MdDFR and MdANS were about6-8folds higher within4days, and the transcription of MdUFGT was about3-5folds higherwithin10days. In addition, the expressions of MdMYB10, MdBHLH3and MdBHLH33 increased sharply at the first day about4.5,1and2folds, respectively. While the expressionof those genes in the control group basically remained stable and lower. This indicated thatMdDFR, MdANS, MdUFGT, MdMYB10and MdBHLH33were the key factors that couldpromote the accumulation of anthocyanin on ‘Ganny Smith’ apples.