The Stringent Response in Phototrophs
The Stringent Response in Phototrophs
复制标题
光养生物的严格反应
作者：
S. Masuda
生物体要生存就必须对环境变化作出反应。因此，物种已经进化出许多细胞内和细胞间的调节系统，这些系统通常反映了生物体的环境。在细菌中，最重要的调控系统之一是严格反应（Cashel et al., 1996）。该信号通过鸟苷5 ' -三磷酸3 ' -二磷酸（pppGpp）和鸟苷5 ‘ -二磷酸3 ’二磷酸（ppGpp）介导，它们作为第二信使发挥作用。40多年前，在大肠杆菌中首次发现了这种严格的反应。当大肠杆菌细胞在营养丰富的条件下生长，然后转移到营养有限的环境中时，细胞内pppGpp和ppGpp （(p)ppGpp）的水平迅速增加（Cashel et al., 1996）。(p)ppGpp控制许多重要的细胞过程，包括转录和翻译。例如(p)ppGpp直接结合RNA聚合酶并改变其启动子结合亲和力（Chatterji et al., 1998; Toulokhonov et al., 2001; Artsimovitch et al., 2004）。因此，当营养物质的可用性发生变化时，严格的反应会同时调整许多基因的转录水平。在大肠杆菌中，(p)ppGpp的合成和降解由RelA和SpoT两种酶催化（Cashel et al., 1996）。缺铁、缺磷、缺氮、缺碳都是触发ppGpp积累的环境压力（Cashel et al., 1996）。对于光合细菌来说，阳光也是重要的“营养物”。对紫色光合细菌——荚膜红杆菌（Rhodobacter capsulatus）的一种SpoT同源物的表征表明，这种严格的响应也能调节光合作用（Masuda & Bauer, 2004）。编码(p)ppGpp合成酶和水解酶的基因在植物中高度保守（van der Biezen et al., 2000; Kasai et al., 2002; Yamada et al., 2003; Givens et al., 2004; Tozawa et al., 2007; Masuda et al., 2008a; Kim et al., 2009），称为RSHs （RelA/SpoT同源物）。所有已知的植物rsh都是针对叶绿体的，表明它们可能控制叶绿体的功能。在这里，我们总结了目前对光养生物的严格反应的理解。关于严格反应本身机制的细节，最近有几篇综述（Magnusson等人，2005；Braeken等人，2006；Jain等人，2006;Ochi, 2007； Potrykus和Cashel, 2008； Srivatsan和Wang， 2008）。
Organisms must respond to environmental changes if they are to survive. As a result, species have evolved numerous intracellular and intercellular regulatory systems that often reflect an organism’s environment. In bacteria, one of the most important regulatory systems is the stringent response (Cashel et al., 1996). Signaling via this response is mediated by guanosine 5’-triphosphate 3’-diphosphate (pppGpp) and guanosine 5’-diphosphate 3’diphosphate (ppGpp), which function as second messengers. The stringent response was first discovered over 40 years ago in Escherichia coli. When E. coli cells are grown under nutrient-rich conditions but then transferred to a nutrient-limited environment, intracellular levels of pppGpp and ppGpp ((p)ppGpp) rapidly increase (Cashel et al., 1996). (p)ppGpp controls many vital cellular processes, including transcription and translation. For example, (p)ppGpp directly binds RNA polymerase and alters its promoter-binding affinity (Chatterji et al., 1998; Toulokhonov et al., 2001; Artsimovitch et al., 2004). When nutrient availability changes, therefore, the stringent response simultaneously adjusts the level of transcription for many genes. In E. coli, synthesis and degradation of (p)ppGpp are catalyzed by two enzymes RelA and SpoT (Cashel et al., 1996). Deficiencies in iron, phosphate, nitrogen, or carbon each represent environmental stresses that trigger (p)ppGpp accumulation (Cashel et al., 1996). For photosynthetic bacteria, sunlight is also an important “nutrient”. Characterization of a SpoT homolog in the purple photosynthetic bacterium, Rhodobacter capsulatus, showed that the stringent response also regulates photosynthesis (Masuda & Bauer, 2004). Genes that encode (p)ppGpp synthases and hydrolases are highly conserved in plants (van der Biezen et al., 2000; Kasai et al., 2002; Yamada et al., 2003; Givens et al., 2004; Tozawa et al., 2007; Masuda et al., 2008a; Kim et al., 2009) and are called RSHs (RelA/SpoT homologs). All known plant RSHs are targeted to chloroplasts, suggesting that they may control chloroplast function. Here we summarize our current understanding of the stringent response in phototrophs. For details concerning the mechanisms of the stringent response itself, several recent reviews are available (Magnusson et al., 2005; Braeken et al., 2006; Jain et al., 2006; Ochi, 2007; Potrykus & Cashel, 2008; Srivatsan & Wang, 2008).
DOI：
10.1098/rstb.2002.1189
发表时间：
2003-01-29
影响因子：
6.3
作者：
Bauer, C;Elsen, S;Masuda, S
通讯作者：
Masuda, S
影响因子：
56.9
作者：
JOHNSON, CH;KNIGHT, MR;TREWAVAS, A
通讯作者：
TREWAVAS, A