Combined Transcriptomic and Metabolomic Analysis Reveals Mechanism of Anthocyanin Changes in Red Maple(Acer rubrum) Leaves

Objective: The autumn leaf color of red maple(Acer rubrum) changed from green to red or yellow, which was closely related to the content of anthocyanin in leaves. With the increasing demand for directional breeding of garden plants, this paper aims to reveal the mechanism of anthocyanin biosynthesis in red maple and provide theoretical basis for directional improvement of its leaf color.Method: In order to analyze the changes of anthocyanin metabolite accumulation and gene expression level, this study employed green leaves, red leaves and yellow leaves of red maple color mutant as experimental materials, and applied UHPLC-QE-MS and high-throughput RNA sequencing method for metabolome and transcriptome analysis, respectively.Result: 1) In the comparison group of red-green leaves, yellow-green leaves, red-yellow leaves, 1 377, 1 793 and 1 098 differential accumulated metabolites were detected respectively under the positive ion mode, 789, 699, 6 778 differential accumulated metabolites were detected respectively under the negative ion mode: in red leaves, the content of cyanidin, pelargonidin and delphinidin and their derivatives increased significantly compared with green leaves; in yellow leaves, the content of cyanidin, delphinidin and its derivatives increased, while the pelargonidin and its derivatives decreased compared with green leaves. 2) In the above-mentioned three comparison groups, transcriptome sequencing detected 28 536, 43 017, 27 110 differentially expressed genes, respectively: compared with green leaves, 89.5% gene expression in the anthocyanidin synthesis pathway of red leaves increased, 66.7% gene expression in the anthocyanidin synthesis pathway of yellow leaves increased. 3) In the anthocyanidin biosynthesis of red maple, there were 29 differentially accumulated metabolites and 48 differentially expressed genes. 4) Network interaction analysis of differential metabolites and genes showed that ANR and LAR genes positively regulate flavonoid products and negatively regulate anthocyanidin derivatives, and ANS and UFGT genes positively regulate anthocyanidin derivatives and negatively regulate flavonoid product.Conclusion: When red maple leaves change color in autumn, the expression of a large number of genes in the anthocyanin pathway is up-regulated, and the content of cyanidin 3-(6"-acetyl-galactoside) and cyanidin 3-arabinoside increased, which is one of the main reasons why leaves change the color. © 2020, Editorial Department of Scientia Silvae Sinicae. All right reserved.