Wild teas are valuable genetic resources for studying domestication and breeding. Here we report the assembly of a high-quality chromosome-scale reference genome for an ancient tea tree. The further RNA sequencing of 217 diverse tea accessions clarifies the pedigree of tea cultivars and reveals key contributors in the breeding of Chinese tea. Candidate genes associated with flavonoid biosynthesis are identified by genome-wide association study. Specifically, diverse allelic function of
CsANR
,
CsF3’5’H
and
CsMYB5
is verified by transient overexpression and enzymatic assays, providing comprehensive insights into the biosynthesis of catechins, the most important bioactive compounds in tea plants. The inconspicuous differentiation between ancient trees and cultivars at both genetic and metabolic levels implies that tea may not have undergone long-term artificial directional selection in terms of flavor-related metabolites. These genomic resources provide evolutionary insight into tea plants and lay the foundation for better understanding the biosynthesis of beneficial natural compounds.
A total of 299,113 unigenes were generated and 15,817 DEGs were identified. We identified candidate genes associated with the regulation of catechins biosynthesis during leaf development in tea plant. The tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most economically significant crops worldwide because of its positive effects on human health. The health benefits of tea are mainly attributed to catechins, which are the predominant polyphenols that accumulate in tea. Catechins are products of the phenylpropanoid and flavonoid biosynthetic pathways. Although catechins were identified in tea leaves long ago, the molecular mechanisms regulating catechins biosynthesis remain unclear. To identify candidate genes involved in catechins biosynthesis, we analyzed the transcriptomes of tea leaves during five different leaf stages of development using RNA-seq. Approximately 809 million high-quality reads were obtained, trimmed, and assembled into 299,113 unigenes with an average length of 565 bp. A total of 15,817 unigenes were differentially expressed during the different stages of leaf development. These differentially expressed genes were enriched in a variety of processes such as the regulation of the cell cycle, starch and sucrose metabolism, photosynthesis, phenylpropanoid biosynthesis, phenylalanine metabolism, and flavonoid biosynthesis. Based on their annotations, 51 of these differentially expressed unigenes are involved in phenylpropanoid and flavonoid biosynthesis. Furthermore, transcription factors such as MYB, bHLH and MADS, which may involve in the regulation of catechins biosynthesis, were identified through co-expression analysis of transcription factors and structural genes. Real-time PCR analysis of candidate genes indicated a good correlation with the transcriptome data. These findings increase our understanding of the molecular mechanisms regulating catechins biosynthesis in the tea plant.
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