Metabolomic and Transcriptomic Analyses Reveal New Insights into the Role of Metabolites and Genes in Modulating Flower Colour of Clematis tientaiensis

Clematis tientaiensis is an ornamental plant with beautiful flowers that belongs to the Ranunculaceae family. C. tientaiensis is endemic to Zhejiang Province in China. Five different colours of the C. tientaiensis flower have been observed, and to explore the reason for this flower colour variation, transcriptome and metabolome sequencing analyses were conducted in this study. The results indicate that 32 metabolites participate in anthocyanin biosynthesis, and that 24 metabolites were differentially accumulated among the five different flower colours. The transcriptome sequencing results enabled the identification of 13,559 differentially expressed genes. Further analysis indicated that cyanidin-3-O-galactosidea and cyanidin-3-O-sophoroside promote anthocyanin accumulation in the flowers of C. tientaiensis, whereas the pelargonidin-3-O-galactoside plays a negative role in anthocyanin synthesis. In addition, a combined transcriptome and metabolome analysis showed that the WDR2 gene plays an important regulatory role in anthocyanin biosynthesis. The results of this study provide a basis for further research into the biosynthesis and regulation of anthocyanins in C. tientaiensis flowers.