| Fruit coloration is one of the most important appearance qualities in apple.Colored fruits tend to attract more consumers and have higher economic value.The color of mature apple fruit is mainly determined by the content of chlorophyll,anthocyanins,and carotenoids.The degradation of chlorophyll can promote the coloring of apple fruit.Studies have shown that exogenous gibberellin(GA)and methyl jasmonate(Me JA)can promote the color change of apple fruit.However,the molecular mechanism still need further elucidate.In this study,to select synergistically regulate anthocyanin biosynthesis genes in apple fruit by GA and Me JA,we analyzed the transcriptome data of Malus domestica ‘Red Fuji’ apple peel treated with exogenous GA and Me JA,and conducted WGCNA and KEGG analysis.The results showed that genes related to chlorophyll metabolism were significantly enriched during GA and Me JA treatment,suggesting that they might be involved in the accumulation of anthocyanins induced by GA and Me JA.We also detected the chlorophyll content and expression levels of key genes in the peel of‘Granny Smith’ treated with GA and Me JA,as well as transient infection of tobacco(Nicotiana tabacum)leaves.The main results of the study are:1.Using the transcriptome data of ‘Red Fuji’ apple peel treated with exogenous GA and Me JA for 0,1,3,5,8 days,we conducted differential expression analysis,and WGCNA analysis combined with the anthocyanin content.We also conducted KEGG enrichment analysis on 898 overlapping genes with high correlation with the Cyanidin-3-O-galactoside in GA and Me JA treated transcriptome data.The results showed that 207 genes were enriched in the metabolic pathway related to chlorophyll synthesis.Mdcy FBP(MD05G1023900)and Mdc FBP1(MD12G1157600)were selected based on annotation information and expression level,which were the key genes related to chlorophyll synthesis.2.The phylogenetic tree and sequence analysis showed that Mdcy FBP and Mdc FBP1 were more closely related to the homologous genes from Rosaceae.In addition,the sequence alignment rate of Mdcy FBP or Mdc FBP1 with its homologous genes in Pistacia vera is low,but their genetic relationship is relatively close,respectively.3.With the increase of lighting time,the green color in the fruit of ‘Granny Smith’disappeared when compared with the control(CK)group.Anthocyanin accumulation was observed in the peel of ‘Granny Smith’ treated with Me JA.4.Chlorophyll degradation is the important for apple fruit coloring at the mature stage.Compared with the CK group,the chlorophyll content in the peel of the fruit treated with GA and Me JA significantly decreased,and the chlorophyll degradation rate was significantly faster than that of the CK group.The chlorophyll content of the hormone treatment group decreased nearly40% compared to the control after 8 days of illumination.At the same time,RT-q PCR results showed that the expression levels of Mdcy FBP and Mdc FBP1 under GA and Me JA treated were significantly lower than those in the CK.5.Mdcy FBP and Mdc FBP1 were silenced in tobacco leaves,tobacco leaves had a significant degreening phenotype after 3 days of infection.The chlorophyll content significantly lower in infected tabacoo leaves than that in control leaves.The results showed that exogenous GA and Me JA could inhibition the expression of Mdcy FBP and Mdc FBP1,thereby promoting the degradation of chlorophyll,thereby beginning the anthocyanin accumulation in apple fruit.In summary,GA and Me JA treatments can regulate the expression of genes related to chlorophyll metabolism,promote chlorophyll degradation,and promote apple fruit coloring. |
