Gene expression regulation of the effect of shading on chlorophyll content in Fuding white tea (Camellia sinensis L.)

Shading is an important practical method to improve the quality of green tea. Previous research of our group found that because the biosynthesis and distribution of theanine in tea plants were affected by down regulation of gene encoding amino acid permeases, theanine content in tea leaves that grown under shading condition was significantly higher than those under natural light. In this study, our group analyzed the changes of tea leaf area, free amino acid content and photosynthetic parameters under natural light and shading conditions, to ensure that moderate shading did not reduce but improved the quality of tea. Transcriptome sequencing and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were conducted to reveal the expression levels of genes related to chlorophyll content and chlorophyll a/b ratio under natural light and shading conditions. Experimental results revealed the presence of the following differentially expressed genes in the porphyrin and chlorophyll metabolism pathway of tea under natural light and shading conditions: the up regulation of CPOX expression may lead to an increase in the accumulation of raw materials of chlorophyll synthesis, while the down regulation of SGR expression may lead to a decrease in chlorophyll degradation. The combined effect of these two genes may lead to an increase in the total chlorophyll content of tea. The down regulation of NOL expression may lead to the obstruction of chlorophyll b transform to chlorophyll a, that is, the decrease of the chlorophyll a/b ratio. This study investigated the molecular mechanism of chlorophyll content and component alteration in Fuding white tea under natural light and shading conditions, and elucidated the effects of different light intensities on the porphyrin and chlorophyll metabolism pathway of tea. Thus, it provided deep understanding of chlorophyll regulation under shading condition in tea cultivation, which could contribute to high-quality matcha production.