Biosynthesis Of Secondary Metabolites Such As Flavonoids And The Expression Of Their Genes In Camellia Sinensis

Tea plant contains abundant secondary metabolites, such as flavonoids, caffeine, theanine, carotenoid and etc, which are closely related to the color, flavor, taste, and health benefits of tea. The concentrations of these secondary metabolites are significantly different in the leaves with different colors, in the buds and leaves of different growth stages, and in the different tissues.In this study, GC-MS was applied to analyze the metabolic profiles of ’Baiye 1’ leaves in different color stages. RNA-seq was applied to analyze the transcriptome profiles of Baiye 1’leaves in different color stages, buds and leaves in different growth stages, and different tissues including flowers and seeds of the ’Longjing 43’. The results and conclusions were summarized as below:1. The metabolic profiles of leaves in white stages and green stage were significantly different. With the color changes and development of the new shoots in early spring, citrate cycle, carbon fixation in photosynthetic organisms and phenylpropanoid biosynthesis pathways were disturbed. The concentration of amino acids, carbohydrates, fatty acids, organic acids and their derivates were significantly different in leaves of different color stages.2. The expression profiles of tea plant leaves with different color were significantly different. From yellow-green stage to white stage and then to green stage, the up-regulated unigenes were mainly involved in photosynthesis, carotenoid biosynthesis, nitrogen metabolism, pentose phosphate pathway and sulfur metabolism. The down-regulated unigenes were mainly involved in anthocyanin biosynthesis. Compared to the green stage, the white stage displayed a significantly higher concentration of P-carotene and the yellow-green stage displayed a significantly lower concentration of lutein. The genes involved in carotenoid biosynthesis were up-regulated from yellow-green stage to white stage and then to green stage. High expression of LCY-b might contribute to the activation of lutein biosynthesis in the green stage. Compared to the green stage, the white stage and yellow-green stage displayed significantly lower concentrations of chlorophyll a and chlorophyll b, respectively. Unigenes which encoding geranylgeranyl diphosphate reductase and chlorophyll b reductase were expressed significantly different in different stages, which might contribute to the different concentrations of chlorophylls. Except for ethylamine, all metabolites including glutamine, glutamate, alanine, and theanine were present at significantly higher concentrations in the yellow-green stage and white stage than in the green stage. Most of the differentially expressed unigenes encoding the key enzymes in the theanine biosynthetic pathway were expressed higher in green stage than in the other stages.3. Transcriptome analysis was performed on different tissues of tea plants, the shared unigenes and tissue-specific unigenes were got in the different tissues. The expressed unigens in the different tissues were quite different; there were more expressed unigenes in the young tissues and less expressed unigenes in the old tissues. The unigenes involved in flavonoids, caffeine and theanine biosynthetic pathways were identified. Among these unigenes, some of them were globally expressed in all tissues, while others were only expressed in distinct tissues. By correlation analysis,339 transcription factors were identified which might participate in the regulation of flavonoid, caffeine and theanine biosynthesis. The number of transcription factor which involved in the regulation of flavonoid, caffeine and theanine biosynthesis was 206,132 and 91, respectively.