Catechins, caffeine, and theanine as three important metabolites in the tea leaves play essential roles in the formation of specific taste and shows potential health benefits to humans. However, the knowledge on the dynamic changes of these metabolites content over seasons, as well as the candidate regulatory factors, remains largely undetermined. An integrated transcriptomic and metabolomic approach was used to analyze the dynamic changes of three mainly metabolites including catechins, caffeine, and theanine, and to explore the potential influencing factors associated with these dynamic changes over the course of seasons. We found that the catechins abundance was higher in Summer than that in Spring and Autumn, and the theanine abundance was significantly higher in Spring than that in Summer and Autumn, whereas caffeine exhibited no significant changes over three seasons. Transcriptomics analysis suggested that genes in photosynthesis pathway were significantly down-regulated which might in linkage to the formation of different phenotypes and metabolites content in the tea leaves of varied seasons. Fifty-six copies of nine genes in catechins biosynthesis, 30 copies of 10 genes in caffeine biosynthesis, and 12 copies of six genes in theanine biosynthesis were detected. The correlative analysis further presented that eight genes can be regulated by transcription factors, and highly correlated with the changes of metabolites abundance in tea-leaves. Sunshine intensity as a key factor can affect photosynthesis of tea plants, further affect the expression of major Transcription factors (TFs) and structural genes in, and finally resulted in the various amounts of catechins, caffeine and theaine in tea-leaves over three seasons. These findings provide new insights into abundance and influencing factors of metabolites of tea in different seasons, and further our understanding in the formation of flavor, nutrition and medicinal function.

中文翻译：

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茶树（茶花）中的儿茶素，咖啡因和茶氨酸生物合成的综合转录组学和代谢组学分析。

儿茶素，咖啡因和茶氨酸是茶叶中的三种重要代谢产物，在形成特定口味中起着至关重要的作用，并显示出对人类健康的潜在益处。然而，关于这些代谢物含量随季节动态变化以及候选调节因子的知识在很大程度上尚不确定。综合的转录组学和代谢组学方法用于分析儿茶素，咖啡因和茶氨酸等三种主要代谢物的动态变化，并探讨在季节变化中与这些动态变化相关的潜在影响因素。我们发现夏季儿茶素的丰度高于春秋季，而茶氨酸的丰度明显高于春秋季。而咖啡因在三个季节中没有显示出明显变化。转录组学分析表明，光合作用途径中的基因被显着下调，这可能与不同季节的茶叶中不同表型和代谢物含量的形成有关。检测到儿茶素生物合成中有9个基因的56个拷贝，咖啡因生物合成中有10个基因的30个拷贝以及茶氨酸生物合成中有6个基因的12个拷贝。相关分析进一步表明，八个基因可以受转录因子的调控，并且与茶叶中代谢产物丰度的变化高度相关。日照强度是一个关键因素，可以影响茶树的光合作用，进一步影响主要转录因子（TFs）和结构基因的表达，最终在三个季节中导致茶叶中含有各种儿茶素，咖啡因和茶氨酸。这些发现为不同季节的茶叶代谢物的丰度及其影响因素提供了新的见解，并进一步加深了我们对风味，营养和药用功能形成的理解。