Abstract: Etiolation is a common morphological variation in tea plants. In those mutants, the contents of the characteristic metabolites change greatly and amino acids are highly accumulated. Studying the reasons of these changes can help to reveal the relationship between leaf color variation and amino acid metabolism. In this study, an etiolated tea plant, which was found accidentally in Shimen area, was used as the research material. As a leaf-color mutant, it has three different colored leaves: yellow, green and yellow-green. The ultrastructure of the chloroplasts, the contents of characteristic metabolites, the expression levels of theanine-related genes (TS, CsGS1, CsGS2) and the correlation between the expression levels and theanine in different leaves were studied. The results show: (1) the chloroplast structure of the yellow leaves was abnormal, which mainly presented as the blurry structure of the thylakoid membrane. (2) the alkaloid contents reduced from yellow, green to yellow-green leaves with significant differences. (3) gallic acid and total catechin contents were the highest in green leaves, and there was no significant difference between the other two groups. The contents of multiple catechins increased as the leaves turned green, but the contents of EC were positively related to the etiolation. (4) the contents of amino acids and theanine increased as the leaves turned yellow. (5) TS and CsGS1 showed the highest expressions in green leaves but the lowest expressions in yellow-green leaves. While CsGS2 exhibited the highest expression in yellow leaves. (6) high theanine content was not related to the expressions of TS, CsGS1 and CsGS2. In summary, the chloroplast structure of etiolated tea plant is abnormal, the metabolism is affected, the amino acid decomposition is inhibited in the etiolated leaves, which result in the enrichment of amino acids.

Key words: etiolated tea plant, theanine, theanine synthetase, glutamine synthetase