Mutations in rpoBC suppress the defects of a Sinorhizobium meliloti relA mutant.
Mutations in rpoBC suppress the defects of a Sinorhizobium meliloti relA mutant.
复制标题
rpoBC 突变抑制苜蓿中华根瘤菌 relA 突变体的缺陷。
DOI：
10.1128/jb.185.18.5602-5610.2003
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发表时间：
2003
影响因子：
3.2
通讯作者：
Long,SharonR
中科院分区：
文献类型：
--
作者：
Wells,DerekH;Long,SharonR
苜蓿中华根瘤菌和苜蓿之间的固氮共生需要双方进行复杂的生理适应。细菌协调控制生理适应的一种方法是严格反应，这是由核苷酸鸟苷四磷酸 (ppGpp) 的存在触发的。 ppGpp 由 RelA 酶产生，被认为可以结合并改变 RNA 聚合酶 (RNAP) 启动和延长转录的能力，并影响核心酶对各种 sigma 因子的亲和力。 AnS。不能产生ppGpp的苜蓿相关突变体先前被证明在形成结节的能力方面存在缺陷。该突变体还会过量产生一种共生必需的胞外多糖，称为琥珀酸聚糖 (38)。这里介绍的工作包括对从宿主植物中分离出来的抑制突变体的分析，这些突变体抑制了相关突变体的共生缺陷。所有抑制突变都是外源性的，并映射到编码 RNAP 的 β 和 β' 亚基的 EitherrpoBorrpoC。表型、结构和基因表达分析表明，抑制突变体可分为两类：一种对严格反应调节基因的作用具有特异性，并且与缺乏ppGpp的大肠杆菌菌株的抑制突变体具有惊人的相似性，另一种与亲本菌株相比降低了所有测试基因的转录。我们的研究结果表明，成功建立共生的能力与细菌通过严格反应进行整体生理调整的能力紧密相关。
The nitrogen-fixing symbiosis betweenSinorhizobium melilotiandMedicago sativarequires complex physiological adaptation by both partners. One method by which bacteria coordinately control physiological adaptation is the stringent response, which is triggered by the presence of the nucleotide guanosine tetraphosphate (ppGpp). ppGpp, produced by the RelA enzyme, is thought to bind to and alter the ability of RNA polymerase (RNAP) to initiate and elongate transcription and affect the affinity of the core enzyme for various sigma factors. AnS. meliloti relAmutant which cannot produce ppGpp was previously shown to be defective in the ability to form nodules. This mutant also overproduces a symbiotically necessary exopolysaccharide called succinoglycan (38). The work presented here encompasses the analysis of suppressor mutants, isolated from host plants, that suppress the symbiotic defects of therelAmutant. All suppressor mutations are extragenic and map to eitherrpoBorrpoC, which encode the β and β′ subunits of RNAP. Phenotypic, structural, and gene expression analyses reveal that suppressor mutants can be divided into two classes; one is specific in its effect on stringent response-regulated genes and shares striking similarity with suppressor mutants ofEscherichia colistrains that lack ppGpp, and another reduces transcription of all genes tested in comparison to that in therelAparent strain. Our findings indicate that the ability to successfully establish symbiosis is tightly coupled with the bacteria's ability to undergo global physiological adjustment via the stringent response.