Integrated Transcriptome and Metabolic Analyses Reveals Novel Insights into Free Amino Acid Metabolism inHuangjinyaTea Cultivar.
The chlorotic tea varietyHuangjinya, a natural mutant, contains enhanced levels of free amino acids in its leaves, which improves the drinking quality of its brewed tea. Consequently, this chlorotic mutant has a higher economic value than the non-chlorotic varieties. However, the molecular mechanisms behind the increased levels of free amino acids in this mutant are mostly unknown, as are the possible effects of this mutation on the overall metabolome and biosynthetic pathways in tea leaves. To gain further insight into the effects of chlorosis on the global metabolome and biosynthetic pathways in this mutant,Huangjinyaplants were grown under normal and reduced sunlight, resulting in chlorotic and non-chlorotic leaves, respectively; their leaves were analyzed using transcriptomics as well as targeted and untargeted metabolomics. Approximately 5,000 genes (8.5% of the total analyzed) and ca. 300 metabolites (14.5% of the total detected) were significantly differentially regulated, thus indicating the occurrence of marked effects of light on the biosynthetic pathways in this mutant plant. Considering primary metabolism, including that of sugars, amino acids, and organic acids, significant changes were observed in the expression of genes involved in both nitrogen (N) and carbon metabolism. The suite of changes not only generated an increase in amino acids, including glutamic acid, glutamine, and theanine, but it also elevated the levels of free ammonium, citrate, and α-ketoglutarate, and lowered the levels of mono- and di-saccharides and of caffeine as compared with the non-chlorotic leaves. Taken together, our results suggest that the increased levels of amino acids in the chlorotic vs. non-chlorotic leaves are likely due to increased protein catabolism and/or decreased glycolysis and diminished biosynthesis of nitrogen-containing compounds other than amino acids, including chlorophyll, purines, nucleotides, and alkaloids.
Tea Research Institute, Chinese Academy of Agricultural SciencesHangzhou, China; Key Laboratory for Plant Biology and Resource Application of Tea, The Ministry of AgricultureHangzhou, China.
Qunfeng
Q
Zhang
Tea Research Institute, Chinese Academy of Agricultural SciencesHangzhou, China; Key Laboratory for Plant Biology and Resource Application of Tea, The Ministry of AgricultureHangzhou, China.
Meiya
M
Liu
Tea Research Institute, Chinese Academy of Agricultural SciencesHangzhou, China; Key Laboratory for Plant Biology and Resource Application of Tea, The Ministry of AgricultureHangzhou, China.
Jianyun
J
Ruan
Camellia sinensis; chlorotic mutation; free amino acid; metabolism; nitrogen metabolism