The stringent response regulates adaptation to darkness in the cyanobacterium Synechococcus elongatus
The stringent response regulates adaptation to darkness in the cyanobacterium Synechococcus elongatus
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DOI：
10.1073/pnas.1524915113
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发表时间：
2016-08-16
影响因子：
11.1
通讯作者：
Savage, David F.
中科院分区：
文献类型：
--
作者：
Hood, Rachel D.;Higgins, Sean A.;Savage, David F.
蓝藻聚球藻依靠光合作用来驱动新陈代谢和生长。在黑暗中，聚球藻停止生长，从其糖原储存中获取能量，并通过未知的机制极大地降低大分子合成的速度。在这里，我们表明严格的反应，一种胁迫反应途径，其基因在细菌和植物质体中是保守的，有助于这种黑暗适应。严格反应警报鸟苷3‘-二磷酸5’-二磷酸(PpGpp)的水平在从光到暗的转变后上升，表明黑暗在蓝藻中引发的反应与异养细菌中的饥饿相同。高水平的ppGpp足以阻止生长并显著改变细胞生理的许多方面，包括光合色素和聚磷酸盐的水平、DNA含量和翻译速度。不能合成ppGpp的细胞在黑暗中暴露后显示出明显的生长缺陷。这种严格的反应调节了聚球藻中许多基因的表达，包括核糖体冬眠促进因子(HPF)，它导致核糖体在黑暗中二聚，可能导致翻译减少。尽管聚球藻的新陈代谢使其有别于其他模式细菌系统，但严格反应的逻辑仍然非常保守，同时已经适应了光合作用生活方式的独特压力。
The cyanobacterium Synechococcus elongatus relies upon photosynthesis to drive metabolism and growth. During darkness, Synechococcus stops growing, derives energy from its glycogen stores, and greatly decreases rates of macromolecular synthesis via unknown mechanisms. Here, we show that the stringent response, a stress response pathway whose genes are conserved across bacteria and plant plastids, contributes to this dark adaptation. Levels of the stringent response alarmone guanosine 3'-diphosphate 5'-diphosphate (ppGpp) rise after a shift from light to dark, indicating that darkness triggers the same response in cyanobacteria as starvation in heterotrophic bacteria. High levels of ppGpp are sufficient to stop growth and dramatically alter many aspects of cellular physiology, including levels of photosynthetic pigments and polyphosphate, DNA content, and the rate of translation. Cells unable to synthesize ppGpp display pronounced growth defects after exposure to darkness. The stringent response regulates expression of a number of genes in Synechococcus, including ribosomal hibernation promoting factor (hpf), which causes ribosomes to dimerize in the dark and may contribute to decreased translation. Although the metabolism of Synechococcus differentiates it from other model bacterial systems, the logic of the stringent response remains remarkably conserved, while at the same time having adapted to the unique stresses of the photosynthetic lifestyle.