Domínguez-Martín Maria Agustina, Gómez-Baena Guadalupe, Díez Jesús, López-Grueso Maria José, Beynon Robert J, García-Fernández José Manuel
Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Agroalimentaria CEIA3, Universidad de Córdoba, Córdoba, Spain.
Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
mSystems. 2017 May 30;2(3). doi: 10.1128/mSystems.00008-17. eCollection 2017 May-Jun.
requires the capability to accommodate to environmental changes in order to proliferate in oligotrophic oceans, in particular regarding nitrogen availability. A precise knowledge of the composition and changes in the proteome can yield fundamental insights into such a response. Here we report a detailed proteome analysis of the important model cyanobacterium SS120 after treatment with azaserine, an inhibitor of ferredoxin-dependent glutamate synthase (GOGAT), to simulate extreme nitrogen starvation. In total, 1,072 proteins, corresponding to 57% of the theoretical proteome, were identified-the maximum proteome coverage obtained for any strain thus far. Spectral intensity, calibrated quantification by the Hi3 method, was obtained for 1,007 proteins. Statistically significant changes ( value of <0.05) were observed for 408 proteins, with the majority of proteins (92.4%) downregulated after 8 h of treatment. There was a strong decrease in ribosomal proteins upon azaserine addition, while many transporters were increased. The regulatory proteins P and PipX were decreased, and the global nitrogen regulator NtcA was upregulated. Furthermore, our data for indicate that NtcA also participates in the regulation of photosynthesis. responds to the lack of nitrogen by slowing down translation, while inducing photosynthetic cyclic electron flow and biosynthesis of proteins involved in nitrogen uptake and assimilation. is the most abundant photosynthetic organism on Earth, contributing significantly to global primary production and playing a prominent role in biogeochemical cycles. Here we study the effects of extreme nitrogen limitation, a feature of the oligotrophic oceans inhabited by this organism. Quantitative proteomics allowed an accurate quantification of the proteome, finding three main responses to nitrogen limitation: upregulation of nitrogen assimilation-related proteins, including transporters; downregulation of ribosome proteins; and induction of the photosystem II cyclic electron flow. This suggests that nitrogen limitation affects a range of metabolic processes far wider than initially believed, with the ultimate goal of saving nitrogen and maximizing the nitrogen uptake and assimilation capabilities of the cell.
为了在贫营养海洋中增殖，尤其是在氮可用性方面，需要具备适应环境变化的能力。对蛋白质组的组成和变化有精确的了解，可以深入洞察这种反应。在此，我们报告了重要模式蓝细菌SS120在用氮杂丝氨酸（一种铁氧化还原蛋白依赖性谷氨酸合酶（GOGAT）的抑制剂）处理后，为模拟极端氮饥饿而进行的详细蛋白质组分析。总共鉴定出1072种蛋白质，占理论蛋白质组的57%，这是迄今为止任何菌株获得的最大蛋白质组覆盖率。通过Hi3方法进行校准定量，获得了1007种蛋白质的光谱强度。观察到408种蛋白质有统计学上的显著变化（P值<0.05），大多数蛋白质（92.4%）在处理8小时后下调。添加氮杂丝氨酸后核糖体蛋白强烈减少，而许多转运蛋白增加。调节蛋白P和PipX减少，全局氮调节因子NtcA上调。此外，我们的数据表明NtcA也参与光合作用的调节。通过减缓翻译来响应氮的缺乏，同时诱导光合循环电子流以及参与氮吸收和同化的蛋白质的生物合成。蓝细菌是地球上最丰富的光合生物，对全球初级生产有重大贡献，并在生物地球化学循环中发挥重要作用。在此我们研究极端氮限制的影响，这是该生物栖息的贫营养海洋的一个特征。定量蛋白质组学能够准确量化蓝细菌的蛋白质组，发现对氮限制的三种主要反应：与氮同化相关的蛋白质（包括转运蛋白）上调；核糖体蛋白下调；以及光系统II循环电子流的诱导。这表明氮限制影响的代谢过程范围比最初认为的要广泛得多，最终目标是节省氮并使细胞的氮吸收和同化能力最大化。
