Metabolome and Transcriptome Analyses of Red-colored Leaves From Eucommia Ulmoides ‘Huazhong No. 12’

Abstract

Background: Eucommia ulmoides ‘Oliver’ is an economically important tree species with highly medicinal and ecological values that is naturally distributed in China. E. ulmoides ‘Huazhong No. 12’ (H12) is the only red-leaf genotype of this species. In this study, the pigment contents of H12 and E. ulmoides ‘Huazhong No. 11’ (H11, green leaves) were determined. The differential metabolites in H12 and H11 were detected by UPLC-MS/MS, and the differentially expressed genes were screened by transcriptome. Then the key metabolites and corresponding gene regulation in anthocyanin related metabolic pathway were analyzed.Results: The chlorophyll a, chlorophyll b and carotenoid contents in H12 leaves were lower than H11, while the total anthocyanin content in H12 was 4.06 times higher than in H11. There were 96 up-regulated metabolites in H12, including anthocyanin, proanthocyanidins, flavonoid and flavonol. Among them, four differentially expressed anthocyanins were identified. A total of 8,368 differentially expressed genes were selected from transcriptome between H12 and H11. The flavone and flavonol biosynthesis pathway, anthocyanin pathway and photosynthetic pathway were analyzed. Finally, EuCHI, EuF3'H, EuF3'5'H, EuDFR and Eu3MaT1 were recommended as the key genes. The cyanidin, cyanidin 3-malonyl-glucoside and cyanidin 3, 5-glucoside were responsible for the H12 red leaves.Conclusion: This study revealed the metabolites and gene regulation of anthocyanin synthesis, and the potential function between the anthocyanin and photosynthetic gene expression in E. ulmoides red leaves. Notably, the results also provided a reference for the study of other plant leaf-coloring mechanisms.