The tea plant has a whopper genome, four times that of coffee, scientists find – Washington Post

From a single species of plant comes many teas. The tea tree, a shrub called Camellia sinensis,produces white, green, black and oolong teas. The tea's destiny is a matter of variables. The final drink reflects the tea cultivar, the growing environment and how the leaves areprocessed dried, crushed, steamed, blended. Farmers pluck baby leaves, as one Snapple commercial put it in the mid-2000s, to begin makingwhite tea.

And yet scientists in China, South Korea and the United States say there is another way to further tea's potential, beyond altering the dirt or the stages of harvest or processing.

DNA analysis could lead toa more diversified set of tea flavors by tracing the genes responsible for taste, according to Lizhi Gao, a botany professor at the Chinese Academy of Sciences' Kunming Institute of Botany. Heand colleagues have completed the first high-quality genome of thetea tree shrub, published this week in the journal Molecular Plant.

The plant took five years to analyze, thanks to the sheer numberof DNA sequences involved. The tea tree genome is extremely large, Gao wrote in an email to The Washington Post counting 3 billion base pairs, about four times the size of coffee's genome.

Of hot and invigorating drinks, coffee getsmost of the buzz, at least in the United States: This country is home to140 million daily coffee drinkersand the StarbucksUnicorn Frappuccino, and Americans consume more coffee than people anywhere else. Researchers sequenced thegenome of robustacoffee in 2014, hinting at a future of genetically modified coffees, as The Post reported at the time. Scientists followed up with the arabica coffee genomein January.

Monday markedthe tea tree's turn. It was a long time coming. Dried plants, recently found in a Chinese mausoleum, revealed that emperors in the Han Dynasty enjoyed tea2,100 years ago, possibly as part of a soup. Thesovereigns were onto something. Today, 3 billion people drink tea, and by one estimate, for everymug of coffee consumed on the planet, humans drinkthree cups of tea.

Gao and hiscolleagues had to churn through the tea tree's huge levels of retrotransposons. These repeated DNA sequences, about 80 percent of the tea genome, duplicated themselves into the genome again and again over 50 million years of tea tree evolution.It is a mystery why retrotransposon sequences are abundant in this plant but not in another, Gao said.

But the researchers were most interested not in size but in the waytea produces tastymolecules. The tea-processing industries in tea-drinking countries, especially in China, have developed numerous tea products with diverse tea flavor, Gao said. But processing techniques alone aren't enough, he said. Tea also depends ondeveloping new plantvarieties, containing unique combinations of flavorful molecules.

Three types of chemicals are most responsible for tea's taste. One is an amino acidonly found in tea, called l-theanine, whichin the last decade has been added todrinks that promote focus andconcentration. (Such focus drinks are of dubious efficacyand lack supporting research.)

The second type of chemical is a class of flavonoid, or plant pigment molecule, called catechins.The third is caffeine, which evolvedin tea independently of cacao and coffee, akin to the way both sea turtles and dolphins evolved flippers separately.

There are several theories as to why plants produce caffeine. Caffeine at high doses is a natural pesticide. Butat low doses, as in some nectars, it may be giving insects a memorable jolt.Caffeine was one tool in tea's repertoire ofdisease defense and environmental stress tolerance methods to help it adapt globally to diverse habitats, Gao said.

The tea genome answered a question the scientist had long pondered: Why can't we make tea from closeCamelliasinensis cousins, such as the tea oil plantCamellia oleifera?

It turns out thatC. oleifera and its 100 other Camelliarelatives do not produce high amounts of the caffeine or catechin family of genes.(Caffeine and catechins are not proteins but secondary metabolites, which means manygenes are required to constructthem.) Put another way, Gao said, the expression levels of caffeine- and catechin-related genes determines the tea processing suitability.

The chief horticulturist at Britain's Royal Horticultural Society, Guy Barter, said plant breeders would welcome this work. Once you understand the basis for the flavors and the processing quality of the tea, you can then have genetic markers that breeders can look for when trying to produce new varieties, he told the BBC.

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The tea plant has a whopper genome, four times that of coffee, scientists find - Washington Post