Effect of shade treatment on theanine biosynthesis in Camellia sinensis seedlings

Theanine synthetase (TS) is a key enzyme involved in theanine biosynthesis. In our recent study, it has been revealed that theanine biosynthesis derived from nitrogen metabolism in tea (Camellia sinensis) plants can be influenced by shading treatment. The expression patterns of CsTS protein in the roots and shoots of tea seedlings were examined by western blot using a self-prepared polyclonal antibody with high specificity and sensitivity. The effect of long-term shade treatment on the levels of theanine synthesis was also investigated using roots and shoots of tea seedlings. Levels of theanine and total free amino acids gradually increased in shoots, reaching their maximum after 22 days of treatment (DOT). The immunoblotting analysis suggested that CsTS protein levels increased gradually up to 22 DOT and expression remained at a high level, except after 1 DOT where levels were low in both roots and shoots. The increased theanine concentration we observed in the shading treatment may be due to increased nitrogen assimilation and reduced theanine catabolism under shade conditions.