Chinese geneticists sequenced the tea tree genome, which helped explain why tea is well adapted to different climatic conditions and is rich in antioxidants and caffeine.
Tea tree Camellia sinensis belongs to the genus Camellia, in which more than 100 species. Previously, scientists have already been able to explain some of the beneficial properties of tea. Thus, the substance epigallocatechin-3-gallate contained in it was able to inhibit the growth of tumor cells. In addition, it turned out that the consumption of tea can significantly reduce the risk of cardiovascular disease and thus prolong life.
Previous studies have shown that tea owes its beneficial properties and aroma to a group of antioxidants called flavonoids. These substances are believed to help plants survive in the environment. One flavonoid with a bitter taste – catechin – is especially associated with the aroma of tea. The levels of catechins and other flavonoids, as well as caffeine, are different in different species of Camellia.
To understand why this is so, Chinese scientists have decoded the Yongkang variety from the Yunnan province of China to the tea tree genome. They found that tea tree leaves contain not one but several copies of the genes that are responsible for the production of caffeine and flavonoids. At the same time, caffeine and flavonoids are not proteins, and therefore are not encoded directly in the genome – they are produced indirectly by other proteins that are encoded.
Genomic analysis of tea showed that it has an extremely large genome compared to most sequenced plant species: it consists of 3 billion base pairs. This is due to the fact that the tea tree genome is very saturated with the so-called retrotransposons that can repeatedly copy and paste themselves into different parts of the genome. In total, the tea genome is 80% composed of these repeating elements. It is their abundance, as scientists believe, that led to the fact that the tea tree has become resistant to disease and is well adapted to various climatic conditions.
As the researchers write in their report, “genes have been discovered that enhance the production of catechin and the activation of stress-resistant enzymes that are important for tea taste and adaptation. It is also shown that tea came to the synthesis of caffeine through its own genetic pathway, separate from cocoa and coffee. "
Thus, a study of 25 species of Camellia showed that higher levels of expression of most flavonoid and caffeine-related genes increase the production of catechins and caffeine and, increasing the resistance of tea to disease, at the same time improve its taste and usefulness to humans.