Tea Tree Genome Contains Clues about Flavor Properties of Tea Leaves
02 May 2017 --- Researchers in China have published the first draft of the cultivated tea tree Camellia sinensis genome in the journal Molecular Plant. According to the researchers, sequencing the tea tree genome could uncover information which will help growers improve breeding efficiency and produce better tea.
The researchers found that the tea tree possesses an “extraordinarily large genome when compared with most sequenced plant species” as well as lineage-specific expansions of genes associated with flavonoid metabolic biosynthesis, “which enhance catechin production, terpene enzyme activation and stress tolerance, important features for tea flavor and adaptation.”
Although there are many species of the genus Camellia, only two major varieties (C. sinensis. var. assamica and C. sinensis var. sinensis) are grown commercially for making tea. Three major characteristic secondary metabolites (catechins, theanine and caffeine) are thought to contribute to tea’s nutritional and medicinal properties, with levels of catechin and caffeinie varying among Camellia species.
In addition, the researchers demonstrated “an independent and rapid evolution of the tea caffeine synthesis pathway relative to cacao and coffee.” Tea processing suitability and tea quality were boosted by higher expression levels of most flavonoid- and caffeine- but not theanine-related genes, which researchers say contribute to the increased production of catechins and caffeine.
Although caffeine and catechins are not encoded in the genome directly, genetically encoded proteins in the tea leaves manufacture them. All Camellia species have genes for the caffeine- and flavonoid-producing pathways, but those genes are expressed at different levels in different species. The variation in levels may explain what makes C. sinensis leaves suitable for making tea.
Future research projects will include double-checking the genome draft and sequencing different tea tree varieties from around the world.
The research was funded by the Yunnan Team Innovation Project, the National Science Foundation of China, the Natural Science Foundation of Yunnan Province, the Kunming Institute of Botany and the Top Talents Program of Yunnan Province. The article is titled “The Tea Tree Genome Provides Insights into Tea Flavor and Independent Evolution of Caffeine Biosynthesis” and is accessible online.
