The Research Of Light-induced MdBBX21 Promoteing Anthocyanin Synthesis In Apple Peel

The color of apple(Malus domestica Borkh.)peel is very important for its nutritional value and economic value.Anthocyanins take the responsibility for red color in apple peels,and light is an indispensable environmental factor during the process of anthocyanin biosynthesis.The regulatory and structural genes of anthocyanin biosynthesis on apple peel would up regulate after expeose to light,while there are still some gaps between light signals and those genes that related to anthocyanin synthesis.In this study,the red apple variety ’Starkimon’ was used as material to analyze the light-induced peel coloring process.The main results obtained in this study are as follows:1.The apple peels after expose to white light 0 h(G0)、6 h(G6)and 24 h(G24)were used for high-throughput sequencing.After normalizing the expression level of differentially expressed genes to G0,the result showed that 4082 differentially expressed genes were classified into two significant up-regulated expression modes(profile6 and profile7)and one significant down-regulated expression mode(profile0).The KEGG enrichment analysis of the differentially expressed genes in the up-regulated expression mode showed that the genes related to flavonoid biosynthesis and phenylpropanoid biosynthesis were significantly enriched.2.As for its highest homology with Arabidopsis At BBX21,a differentially expressed gene MD08G1021000 identified from profile6 was named Md BBX21.Md BBX21 was able to respond to white light,and its relative expression level begun to increase at 3 h and reached a peak at 9 h in the peel of ‘Starkrimson’ apple after exposed to white light.What’s more,it’s changing was earlier than that of structural genes and regulatory genes which related to anthocyanin synthesis,indicating that Md BBX21 could be induced by light quickly,and may play a role in the light response process.3.The functional verification of Md BBX21 was carried out and the results of subcellular localization revealed that Md BBX21 was localized in the nucleus.After Md BBX21 was ectopic overexpressed on Arabidopsis thaliana further,the result showed that there were more anthocyanin accumulation in seedings of transgenic overexpression arabidopsis thaliana,indicating that Md BBX21 could promote the biosynthesis of anthocyanin.4.Yeast two-hybrid assay and bimolecular fluorescence complementation(Bi FC)experiment verified the interaction between the Md BBX21 and Md HY5 protein in yeast cells and living plant cells respectively.5.The dual luciferase system was carried out to detect the effect of Md BBX21 on the Md MYB10 promoter.The results show that Md BBX21 protein could promote the transcriptional activation of the Md MYB10 promoter,while when Md BBX21-p Green II62-SK was mixed with Md HY5-p Green II 62-SK and Pro MYB10-LUC to inject tobacco leaves,the LUC activity is significantly increased.It showed that Md BBX21 can interact with Md HY5 proetin to promote the transcriptional activation of Md MYB10 promoter.