Strong biosynthesis and weak catabolism of theanine in new shoots contribute to the high theanine accumulation in Albino/etiolated tea plant (Camellia sinensis)

Tea processed from albino/etiolated tea shoots is favored by consumers because of its high theanine accumulation. To explore why theanine accumulates highly in new shoots of albino/etiolated tea cultivars, we compared theanine content in shoots and roots of albino/etiolated and common green tea cultivars. Results suggested that high theanine accumulation in albino/etiolated tea shoots was likely not caused by higher theanine biosynthesis in roots. Further analyses suggested that CsAlaDC-catalyzed ethylamine biosynthesis and CsGOGAT1-catalyzed glutamate biosynthesis were more active, and CsGGT2-catalyzed theanine catabolism was weaker in new shoots of these albino/etiolated tea plant cultivars. Therefore, the high theanine accumulation in albino/etiolated shoots is probably contributed by the strong theanine biosynthesis and weak catabolism in new shoots. These findings provided more comprehensive insights into the high accumulation of theanine in new shoots of albino/etiolated tea cultivars, and the knowledge can be used in plant breeding for new cultivars with higher theanine accumulation.