State Key Laboratory of Tea Biology and Utilization, Anhui Agricultural University, Hefei, Anhui 230036, People's Republic of China.
J Agric Food Chem. 2021 Sep 1;69(34):10002-10016. doi: 10.1021/acs.jafc.1c02589. Epub 2021 Aug 18.
Theanine and flavonoids (especially proanthocyanidins) are the most important and abundant secondary metabolites synthesized in the roots of tea plants. Nitrogen promotes theanine and represses flavonoid biosynthesis in tea plant roots, but the underlying mechanism is still elusive. Here, we analyzed theanine and flavonoid metabolism in tea plant roots under nitrogen deficiency and explored the regulatory mechanism using proteome and ubiquitylome profiling together with transcriptome data. Differentially expressed proteins responsive to nitrogen deficiency were identified and found to be enriched in flavonoid, nitrogen, and amino acid metabolism pathways. The proteins responding to nitrogen deficiency at the transcriptional level, translational level, and both transcriptional and translational levels were classified. Nitrogen-deficiency-responsive and ubiquitinated proteins were further identified. Our results showed that most genes encoding enzymes in the theanine synthesis pathway, such as , , and , were repressed by nitrogen deficiency at transcriptional and/or protein level(s). While a large number of enzymes in flavonoid metabolism were upregulated at the transcriptional and/or translational level(s). Importantly, the ubiquitylomic analysis identified important proteins, especially the hub enzymes in theanine and flavonoid biosynthesis, such as CsAlaDC, CsTSI, CsGS, CsPAL, and CsCHS, modified by ubiquitination. This study provided novel insights into the regulation of theanine and flavonoid biosynthesis and will contribute to future studies on the post-translational regulation of secondary metabolism in tea plants.
茶氨酸和类黄酮（尤其是原花青素）是茶树根部合成的最重要和最丰富的次生代谢物。氮促进茶氨酸的合成，抑制茶树根部类黄酮的生物合成，但潜在的机制仍不清楚。在这里，我们分析了氮缺乏条件下茶树根部的茶氨酸和类黄酮代谢，并结合蛋白质组和泛素组谱以及转录组数据探索了调控机制。鉴定了对氮缺乏有反应的差异表达蛋白，并发现它们富集在类黄酮、氮和氨基酸代谢途径中。对转录水平、翻译水平和转录和翻译水平都有反应的蛋白质进行了分类。进一步鉴定了氮响应和泛素化的蛋白质。我们的结果表明，大多数编码茶氨酸合成途径中酶的基因，如 、 、和 ，在转录和/或蛋白水平受到氮缺乏的抑制。而大量参与类黄酮代谢的酶在转录和/或翻译水平被上调。重要的是，泛素组学分析鉴定了一些重要的蛋白质，特别是茶氨酸和类黄酮生物合成中的关键酶，如 CsAlaDC、CsTSI、CsGS、CsPAL 和 CsCHS，它们被泛素化修饰。这项研究为茶氨酸和类黄酮生物合成的调控提供了新的见解，并将有助于未来对茶树次生代谢物的翻译后调控的研究。
