STiR coffee and tea magazine

28 STiR coffee and tea / Issue 3, 2017 (June/July) *Citation: Xia et al., The Tea Tree Genome Provides Insights into Tea Flavor and Independent Evolution of Caffeine Biosynthesis, Molecular Plant (2017) Dr. Virginia Utermohlen Lovelace CreateSpace Inde- pendent Publishing Platform, 2017 86 pages One of the most remarkable aspects of C. sinensis is how it has managed to find a niche and thrive on every continent except Antarctica. The publication of tea tree's genetic code* by scientists at the Kunming Institute of Botany in China gives us critical clues to its hardi- ness and tastiness. The tea tree in question was a Camellia sinensis var. Assamica, grown in Yunnan Province, China. After they figured out this DNA code, they were able to look into the codes of a number of other Camellia cultivars, and compare these codes to those of other plants. As we all know, plants can't run away from danger, so they develop chemical strate- gies to deal with both disease and environmental changes. These chemical strategies yield the compounds that not only help the plant survive and reproduce, but also provide the flavor we enjoy in the cup. Chemical strategies are dictated by the plant's genes. The larger the number of de- fense genes, the larger the repertoire of strategies, and the better the plant can endure attacks and thrive. It turns out that tea trees have a huge genome (as the collection of genes in an organism's DNA is known). It has about 36% more genes than coffee plants, and 19% more genes than cacao! The tea tree's huge genome comes from duplication of portions of the plant's DNA, coupled with two rounds of duplication of the entire genome over the course of the past 60 million or so years. Normally plants (and animals, too) have the ability to weed out muta- tions and errors in the DNA copying process, so that when duplications occur, they may be removed in whole or in part. It seems that the tea tree is inefficient at pruning its DNA. The result: its enormous genome, particularly enriched in duplicates of genes that give us caffeine and catechins, the bitter compounds in tea; L-theanine, which imparts a savory/ sweet quality to tea; and terpenes, which give teas their aromatic qualities. What Knowing the Tea Tree Genome Means to the Flavors in our Cup By Dr. Virginia Utermohlen Lovelace organism) has a complete complement of genes. What distinguishes individual cells is the activity of the differ- ent genes. For example, in ourselves, the ability to make odor receptors is turned on in our olfactory tissue, while the stomach you get cells making digestive enzymes. The authors of the study explored where in the plant genes were turned to produce catechins, caffeine, and L-theanine. Gene activity for the production of L-theanine was the same in all parts of the plant, but gene activity for the production of caffeine and catechins was highest in "tender shoots" and seeds. If you think about it, the results are not really surprising: the tender shoots are the most vulnerable part of the plant to sunburn (resisted by catechins) and insects (resisted by caffeine and a host of other compounds). This observation supports our prefer- ence for first flush tippy teas. Researchers armed with this genetic information can now begin a systematic exploration at the molecular level of wild relatives of cultivated tea. They can search for variants with specific properties. With luck, such an ex- ploration will lead to development of desirable character- istics in cultivated trees, and slow down the over-plucking that is leading to the decline of precious wild trees. Virginia Utermohlen Lovelance, MD is the author of Three Basic Teas & How to Enjoy Them. Virginia retired as a faculty member in the Division of Nutritional Sciences at Cornell University, Ithaca, New York. Learn more: www.pairteas.com While we enjoy the results of this gene duplication process in our cup, the tea tree enjoys it through survival in a wide range of environments, wider than that of either coffee or cacao trees. The catechins, for example, serve as a sunblock, while caffeine, L-theanine, and terpenes can deter insects. Importantly the more copies of the genes for making these compounds a Camellia plant has, the greater the amount of these compounds produced, and the healthier the tree remains. Which brings me to yet another aspect of the discov- ery that is so important for understanding tea. If you have ever wondered why the tender leaf shoots most often provide the most flavorful teas, the authors provide the biology behind the answer. But first, you should know that each cell in a tea leaf (and in our bodies, too, and in every multicellular specific climates. We can sequence these accessions and compare those se- quences to those from accessions that perform poorly and identify regions of the genome that are correlated with improved performance. Having a genome gives us a framework to which we can align all of our sequencing data, making this process much more straight forward and faster," he said. It will probably take 15 years to breed and select new cultivars, according to Apostolides. "We will be able to breed designer-cultivars for e.g. high or low caffeine or any other trait. This information will also enable us to breed new culti- vars with combinations of more than one traits, e.g. fast fermenters for black tea, that are high in health promoting antioxidants (catechins), that have high yield and are drought and cold tolerant, with good aroma and horizontal leaf poise," he predicts. New cultivars have been developed by clas- sical breeding and selection in other annual and tree crops, based on knowledge of their genome sequences, he said. "I am confident that new tea cultivars will be de- veloped for tea now that the tea genome has been published," he said. "Scientists in all tea producing countries will be able to use the tea genome sequence to develop new cultivars, suited to their climates. "This will require, however, that tea breeders improve their bioinformatics skills to be able to use the information of the tea genome sequence to their full advantage," he concludes.

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