Expression profiling of four RelA/SpoT-like proteins, homologues of bacterial stringent factors, in Arabidopsis thaliana
Expression profiling of four RelA/SpoT-like proteins, homologues of bacterial stringent factors, in Arabidopsis thaliana
复制标题
DOI：
10.1007/s00425-008-0758-5
复制
发表时间：
2008-09-01
期刊：
影响因子：
4.3
通讯作者：
Ohta, Hiroyuki
中科院分区：
文献类型：
--
作者：
Mizusawa, Kazuki;Masuda, Shinji;Ohta, Hiroyuki
严格的反应是细菌适应环境胁迫(如氨基酸饥饿)的最重要的调节系统之一。这种反应是由一种不寻常的核苷酸-3‘，5’-双(焦磷酸)鸟苷(PpGpp)介导的，其水平受RELA和SPOT两种酶的控制。PpGpp显著影响细菌细胞的一系列生理活动，包括转录和翻译，以及几种代谢途径的酶活性。最近，在植物中发现了越来越多的RelA/Spot同源物，命名为RSH。拟南芥有四个RHS(AtRSH1、AtRSH2、AtRSH3和AtCRSH)。为了揭示拟南芥RSH基因的具体作用，我们分析了四个RHS基因的ppGpp合成酶活性，并对RSH基因的表达模式进行了表征。目前和以前的研究结果表明，所有四种RSH蛋白都被定位到质体中。对大肠杆菌突变体的互补分析表明，AtRSH2、AtRSH3和AtCRSH具有ppGpp合成酶活性，而AtRSH1没有。利用报告基因融合的启动子分析表明，4个拟南芥RSH基因在绿色组织和花中表达，这表明RSH功能参与了叶绿体的发育和繁殖。我们还观察到，所有的RSH转录本都表现出昼夜节律，并且AtRSH1和AtRSH2转录本的诱导对几种环境胁迫都有反应。这些结果表明，这四个RSH基因的表达是协同调节的，依赖ppGpp的质体严格反应在高等植物的生理中具有一定的作用。
The stringent response is one of the most important regulatory systems in bacteria for adaptation to environmental stresses such as amino acid starvation. This response is mediated by an unusual nucleotide, guanosine 3',5'-bis(pyrophosphate) (ppGpp), the levels of which are controlled by two enzymes, RelA and SpoT. ppGpp dramatically influences a broad range of physiological activities in bacterial cells, including transcription and translation as well as the enzymatic activities of several metabolic pathways. Recently, a growing number of RelA/SpoT homologues, designated RSH, have been identified in plants. Arabidopsis has four RSHs (AtRSH1, AtRSH2, AtRSH3 and AtCRSH). In order to reveal the specific roles of the individual Arabidopsis RSHs, we have analyzed the ppGpp synthase activities of the four RSHs and characterized the expression pattern of the RSH genes. Results from the present and previous studies indicate that all four RSH proteins are targeted into plastids. Complementation analysis of E. coli mutants revealed that AtRSH2, AtRSH3 and AtCRSH, but not AtRSH1, have ppGpp synthetase activity. Promoter analysis using reporter gene fusions indicated that the four Arabidopsis RSH genes are expressed in green tissues and flowers, suggesting the involvement of RSH functions in chloroplast development and reproduction. We also observed that all RSH transcripts exhibit a diurnal rhythm, and that induction of AtRSH1 and AtRSH2 transcripts are responsive to several environmental stresses. These results suggest that expression of the four RSH genes is coordinately regulated and that the ppGpp-dependent plastid stringent response has certain roles in the physiology of higher plants.