Laboratory of Bioinformatics, Biomathematics and Biostatistics - LR16IPT09, Institut Pasteur de Tunis, Université de Tunis el Manar, Tunis, 1002, Tunisia.
Laboratory of Molecular Epidemiology and Experimental Pathology - LR11IPT04, Institut Pasteur de Tunis, Université de Tunis el Manar, Tunis, 1002, Tunisia.
Sci Rep. 2018 Jan 15;8(1):759. doi: 10.1038/s41598-017-18839-0.
Actinorhizal plants are ecologically and economically important. Symbiosis with nitrogen-fixing bacteria allows these woody dicotyledonous plants to colonise soils under nitrogen deficiency, water-stress or other extreme conditions. However, proteins involved in xerotolerance of symbiotic microorganisms have yet to be identified. Here we characterise the polyethylene glycol (PEG)-responding desiccome from the most geographically widespread Gram-positive nitrogen-fixing plant symbiont, Frankia alni, by next-generation proteomics, taking advantage of a Q-Exactive HF tandem mass spectrometer equipped with an ultra-high-field Orbitrap analyser. A total of 2,052 proteins were detected and quantified. Under osmotic stress, PEG-grown F. alni cells increased the abundance of envelope-associated proteins like ABC transporters, mechano-sensitive ion channels and Clustered Regularly Interspaced Short Palindromic Repeats CRISPR-associated (cas) components. Conjointly, dispensable pathways, like nitrogen fixation, aerobic respiration and homologous recombination, were markedly down-regulated. Molecular modelling and docking simulations suggested that the PEG is acting on Frankia partly by filling the inner part of an up-regulated osmotic-stress large conductance mechanosensitive channel.
共生固氮放线菌在生态和经济上都很重要。这些木本双子叶植物与固氮细菌共生，可以在氮缺乏、水分胁迫或其他极端条件下定殖土壤。然而，与共生微生物的耐旱性相关的蛋白质尚未被鉴定。在这里，我们通过下一代蛋白质组学，利用配备超高场轨道阱分析仪的 Q-Exactive HF 串联质谱仪，对地理分布最广泛的革兰氏阳性固氮植物共生菌弗兰克氏菌（Frankia）的聚乙二醇（PEG）响应脱水蛋白进行了表征。共检测到并定量了 2052 种蛋白质。在渗透压胁迫下，PEG 培养的弗兰克氏菌细胞增加了 ABC 转运蛋白、机械敏感离子通道和规律成簇间隔短回文重复 CRISPR 相关（cas）组件等包膜相关蛋白的丰度。同时，固氮、需氧呼吸和同源重组等可有可无的途径明显下调。分子建模和对接模拟表明，PEG 部分通过填充上调的渗透压大电导机械敏感通道的内部来作用于弗兰克氏菌。
