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
[www.isaaa.org] 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
[www.isaaa.org] 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.



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