Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2016 Nov 29;6:37976. doi: 10.1038/srep37976.
Senescence is the final stage of leaf growth and development. Many different physiological activities occur during this process. A comprehensive metabolomics analysis of tobacco middle leaves at 5 different developmental stages was implemented through multi-platform methods based on liquid chromatography, capillary electrophoresis and gas chromatography coupled with mass spectrometry. In total, 412 metabolites were identified, including pigments, sterols, lipids, amino acids, polyamines, sugars and secondary metabolites. Dramatic metabolic changes were observed. Firstly, membrane degradation and chlorophyll down-regulation occurred after the 50% flower bud stage. Levels of major membrane lipids decreased, including those of the glycolipids in chloroplast thylakoids and phospholipids in membrane envelopes. Clear decreases in free sterols and acylated sterol glucosides were detected along with the accumulation of sterol esters. The accumulation of alkaloids was found. The amino acid levels were significantly decreased, particularly those of N-rich amino acids (glutamine and asparagine), thus reflecting N translocation. Subsequently, the antioxidant system was activated. Sugar alcohols and polyphenols accumulated when the lower leaves turned yellow. These results comprehensively revealed the metabolic changes that occur during tobacco leaf development and senescence under natural conditions.
衰老（Senescence）是叶片生长和发育的最后阶段。在此过程中会发生许多不同的生理活动。通过基于液相色谱、毛细管电泳和气相色谱与质谱联用的多平台方法，对 5 个不同发育阶段的烟草中叶进行了全面的代谢组学分析。共鉴定出 412 种代谢物，包括色素、甾醇、脂类、氨基酸、多胺、糖和次生代谢物。观察到明显的代谢变化。首先，在 50%花蕾期后发生膜降解和叶绿素下调。主要膜脂水平下降，包括质体类囊体中的糖脂和膜包被中的磷脂。酰化甾醇葡萄糖苷与游离甾醇一起明显减少。发现生物碱积累。氨基酸水平显著降低，尤其是富含氮的氨基酸（谷氨酰胺和天冬酰胺），因此反映了氮的转移。随后，抗氧化系统被激活。当下部叶片变黄时，糖醇和多酚积累。这些结果全面揭示了烟草叶片在自然条件下发育和衰老过程中的代谢变化。
