Temperature above the physiological optimum is a stress condition frequently faced by bacteria in their natural environments. Here, we were interested in the correlation between levels of RNA and protein under heat stress. Changes in RNA and protein levels were documented in cultures of Rhodobacter sphaeroides using RNA sequencing, quantitative mass spectrometry, western blot analysis, in vivo [³⁵S] methionine-labelling and plasmid-borne reporter fusions. Changes in the transcriptome were extensive. Strikingly, the proteome remained unchanged except for very few proteins. Examples include a heat shock protein, a DUF1127 protein of unknown function and sigma factor proteins from leaderless transcripts. Insight from this study indicates that R. sphaeroides responds to heat stress by producing a broad range of transcripts while simultaneously preventing translation from nearly all of them, and that this selective production of protein depends on the untranslated region of the transcript. We conclude that measurements of transcript abundance are insufficient to understand gene regulation. Rather, translation can be an important checkpoint for protein expression under certain environmental conditions. Furthermore, during heat shock, regulation at the level of transcription might represent preparation for survival in an unpredictable environment while regulation at translation ensures production of only a few proteins.

中文翻译：

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热应激反应期间球形红杆菌中蛋白质表达的主要检查点发生在翻译水平

高于生理最佳值的温度是细菌在其自然环境中经常面临的压力条件。在这里，我们对热应激下 RNA 和蛋白质水平之间的相关性感兴趣。使用 RNA 测序、定量质谱、蛋白质印迹分析、体内[ ³⁵ S] 蛋氨酸标记和质粒携带的报告融合，记录了球形红杆菌培养物中 RNA 和蛋白质水平的变化。转录组的变化是广泛的。引人注目的是，除了极少数蛋白质外，蛋白质组保持不变。例子包括热休克蛋白、未知功能的 DUF1127 蛋白和来自无前导转录物的 sigma 因子蛋白。这项研究的见解表明，R. sphaeroides通过产生广泛的转录物来应对热应激，同时阻止几乎所有转录物的翻译，并且这种蛋白质的选择性生产取决于转录物的非翻译区域。我们得出结论，转录丰度的测量不足以理解基因调控。相反，翻译可能是某些环境条件下蛋白质表达的重要检查点。此外，在热休克期间，转录水平的调节可能代表了在不可预测的环境中生存的准备，而翻译调节确保仅产生少数蛋白质。