Symbiotic Performance of Sinorhizobium meliloti Lacking ppGpp Depends on the Medicago Host Species.
Symbiotic Performance of Sinorhizobium meliloti Lacking ppGpp Depends on the Medicago Host Species.
复制标题
缺乏 ppGpp 的苜蓿中华根瘤菌的共生性能取决于苜蓿宿主种类。
DOI：
10.1094/mpmi-11-18-0306-r
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Long,SharonR
中科院分区：
文献类型：
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作者：
Wippel,Kathrin;Long,SharonR
豆科植物和根瘤菌之间的根瘤共生中的宿主特异性对于建立成功的相互作用和向植物提供氨至关重要。在相互作用的早期阶段，植物-细菌信号交换介导的特异性。我们观察到，一个缺乏启动细菌严格反应的苜蓿中华根瘤菌突变体AperrelA，不能结瘤苜蓿（紫花苜蓿），但成功地感染苜蓿。我们使用生物化学、组织学、转录组学和成像方法比较S.苜蓿草木樨A突变体和野生型（WT）在两种植物宿主上的差异。在M上，AlprelA表现几乎与WT相似。除了固氮能力降低和根瘤细胞内类杆菌的无序定位外，与此相反，苜蓿根瘤菌A表现出受损的根定殖，未能感染根瘤原基。用苜蓿黄酮木樨草素处理的拟南芥细胞和由突变体onM诱导的成熟根瘤的全局转录组分析。截短型则表现为胞外多糖合成基因的过度表达和植物防御样反应的轻微抑制。许多RelA依赖的转录物与低渗透压相关的FeuP调节子重叠，或者是应激反应的特征。根据我们的研究结果，我们认为RelA是不是必不可少的，直到共生的后期阶段与M。蒺藜，其中它可能参与优化固氮的过程。
Host specificity in the root-nodule symbiosis between legumes and rhizobia is crucial for the establishment of a successful interaction and ammonia provision to the plant. The specificity is mediated by plant-bacterial signal exchange during early stages of interaction. We observed that aSinorhizobium melilotimutant ∆relA, which is deficient in initiating the bacterial stringent response, fails to nodulateMedicago sativa(alfalfa) but successfully infectsMedicago truncatula. We used biochemical, histological, transcriptomic, and imaging approaches to compare the behavior of theS. meliloti ∆relAmutant and wild type (WT) on the two plant hosts. ∆relAperformed almost WT-like onM. truncatula, except for reduced nitrogen-fixation capacity and a disorganized positioning of bacteroids within nodule cells. In contrast, ∆relAshowed impaired root colonization on alfalfa and failed to infect nodule primordia. Global transcriptome analyses of ∆relAcells treated with the alfalfa flavonoid luteolin and of mature nodules induced by the mutant onM. truncatularevealed normalnodgene expression but overexpression of exopolysaccharide biosynthesis genes and a slight suppression of plant defense-like reactions. Many RelA-dependent transcripts overlap with the hypo-osmolarity–related FeuP regulon or are characteristic of stress responses. Based on our findings, we suggest that RelA is not essential until the late stages of symbiosis withM. truncatula, in which it may be involved in processes that optimize nitrogen fixation.