Department of Plant Sciences and Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot 76100, Israel.
Proc Natl Acad Sci U S A. 2014 Feb 18;111(7):2740-5. doi: 10.1073/pnas.1319773111. Epub 2014 Feb 3.
Diatoms are ubiquitous marine photosynthetic eukaryotes responsible for approximately 20% of global photosynthesis. Little is known about the redox-based mechanisms that mediate diatom sensing and acclimation to environmental stress. Here we used a quantitative mass spectrometry-based approach to elucidate the redox-sensitive signaling network (redoxome) mediating the response of diatoms to oxidative stress. We quantified the degree of oxidation of 3,845 cysteines in the Phaeodactylum tricornutum proteome and identified approximately 300 redox-sensitive proteins. Intriguingly, we found redox-sensitive thiols in numerous enzymes composing the nitrogen assimilation pathway and the recently discovered diatom urea cycle. In agreement with this finding, the flux from nitrate into glutamine and glutamate, measured by the incorporation of (15)N, was strongly inhibited under oxidative stress conditions. Furthermore, by targeting the redox-sensitive GFP sensor to various subcellular localizations, we mapped organelle-specific oxidation patterns in response to variations in nitrogen quota and quality. We propose that redox regulation of nitrogen metabolism allows rapid metabolic plasticity to ensure cellular homeostasis, and thus is essential for the ecological success of diatoms in the marine ecosystem.
硅藻是一种普遍存在的海洋光合真核生物，约占全球光合作用的 20%。目前对于介导硅藻感知和适应环境胁迫的基于氧化还原的机制知之甚少。在这里，我们使用基于定量质谱的方法来阐明介导硅藻对氧化应激反应的氧化还原敏感信号网络（氧化还原组）。我们量化了菱形藻蛋白质组中 3845 个半胱氨酸的氧化程度，并鉴定了大约 300 个氧化还原敏感蛋白。有趣的是，我们发现了许多组成氮同化途径和最近发现的硅藻脲循环的酶中的氧化还原敏感硫醇。与这一发现一致的是，通过（15）N 的掺入测量的硝酸盐转化为谷氨酰胺和谷氨酸的通量在氧化应激条件下受到强烈抑制。此外，通过将氧化还原敏感 GFP 传感器靶向到各种亚细胞定位，我们绘制了细胞器特异性氧化模式，以响应氮定额和质量的变化。我们提出，氮代谢的氧化还原调节允许快速的代谢可塑性，以确保细胞内稳态，因此对于硅藻在海洋生态系统中的生态成功至关重要。
