Crop Biotech Update

Tea Tree Genome Reveals Insights on Its Flavor, Evolution of Caffeine Biosynthesis

May 10, 2017

Tea is the oldest and most popular nonalcoholic caffeine-containing beverage in the world consumed by more than 3 billion people across 160 countries. Despite its immense cultural and economic significance, little is known about the shrub behind tea leaves.

The most popular varieties of tea—including black tea, green tea, Oolong tea, white tea, and chai—all come from the leaves of Camellia sinensis, known as the tea tree. "There are many diverse flavors, but the mystery is what determines or what is the genetic basis of tea flavors?" says plant geneticist Lizhi Gao of Kunming Institute of Botany in China.

Previous studies suggest that tea gets its flavor from flavonoids, a group of antioxidants. Cathechin, a bitter-tasting flavonoid is associated with tea flavor. Catechin levels and other flavonoids vary among species, as does caffeine. Gao and his colleagues found that C. sinensis leaves not only contain high levels of catechins, caffeine, and flavonoids, but also have multiple copies of the genes that produce caffeine and flavonoids.

All Camellia species have genes for the caffeine- and flavonoid-producing pathways, but each species expresses those genes at different levels, which explains why C. sinensis leaves are suitable for making tea, while other species' leaves aren't. Gao and his colleagues estimate that more than half of the base pairs (67%) in the tea tree genome are part of retrotransposon sequences, or "jumping genes". A tough genome to assemble at 3.02 billion base pairs in length, the tea tree genome is more than four times the size of the coffee plant genome and much larger than most sequenced plant species.

For more details, read the open-access paper in the journal Molecular Plant.