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article imageUnpicking the key to better tea through genomics

By Tim Sandle     May 2, 2017 in Science
Scientists have undertaken the monumental task of sequencing the genome of the tea plant Camellia sinensis. Knowing this will help trace back the origins of tea and it might lead to improvements in the taste of the beverage.
The world’s most popular types of tea, such as black tea, green tea, Oolong tea, white tea, and chai, all come from the leaves of one evergreen shrub: Camellia sinensis. Although tea is of great economic importance, little has been known about the shrub. This has now changed following the revelation of the tea tree genome.
It is hoped the sequencing of the genome will reveal more about the origins of tea and also help biologists to understand why the tea plant is rich in antioxidants and caffeine. Tea's flavor comes primarily from flavonoids, a type of anti-oxidant. Like caffeine, flavonoids are produced by proteins in the tea plant's leaves, so the genes that code for those proteins are ultimately responsible.
The study may also lead to improvements in flavor. As humans have moved tree plants to different regions (most notably from China to India) and cultivated plants over centuries this becomes a form of genetic modification. Does the tea we drink today, for example, taste the same as it did 200 years ago? This question can be answered in time once key genetic markers are identified.
This is not straightforward, since genus Camellia contains over 100 species. The most common tea producing species are C. sinensis. var. assamica and C. sinensis var. sinensis. The other species range from the plant that produces tea tree oil to ornamental shrubs.
Interviewed by the BBC, plant geneticist Dr. Lizhi Gao of Kunming Institute of Botany, China, who led the research, said: “There are many diverse flavors, but the mystery is what determines or what is the genetic basis of tea flavors?” A Phys.Org points out, all Camellia species have genes for the caffeine- and flavonoid-producing pathways, but each species expresses those genes at different levels. Why this is so remains a mystery.
The sequencing project took many years and required the application of the most advanced molecular techniques. The tea genome is far more complex than that of the coffee plant, at three billion DNA base pairs in length. The first plant genome was sequenced fifteen years ago, a somewhat simpler life form.
It is hoped the impact of the research will aid those in the breeding of tea and those who breed plants used medicinally and in cosmetics.
The genome of the tea tree has been published the journal Molecular Plant. The research paper is titled “The Tea Tree Genome Provides Insights into Tea Flavor and Independent Evolution of Caffeine Biosynthesis.”
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