A Sinorhizobium meliloti osmosensory two-component system required for cyclic glucan export and symbiosis
A Sinorhizobium meliloti osmosensory two-component system required for cyclic glucan export and symbiosis
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DOI：
10.1111/j.1365-2958.2008.06304.x
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发表时间：
2008-07-01
影响因子：
3.6
通讯作者：
Long, Sharon R.
中科院分区：
文献类型：
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作者：
Griffitts, Joel S.;Carlyon, Rebecca E.;Long, Sharon R.
通过对固氮豆类共生菌Sinorhizobium Meliloti新的共生突变体的筛选，发现了可能的反应调节因子FeuP在共生侵染过程中的关键作用。转录组分析表明，FeuP控制着至少16个基因的转录，其中包括编码依赖于ATP的环β-葡聚糖出口商的ndvA。FeuP功能的丧失导致了与环状β-葡聚糖生物合成缺陷相关的特征，包括在低渗透条件下生长和运动能力差，以及在共生感染的早期阶段无法入侵植物组织。对环状葡聚糖的分析表明，feuP突变体能够合成细胞内的环状β-葡聚糖，但不能将其输出。通过ndvA的组成性表达可以将环状β-葡聚糖输出恢复到feuP突变细胞中；同样，异位表达ndvA可以挽救feuP突变的共生表型。我们进一步表明，连接的感受器激酶基因FEUQ对调控ndvA转录也是重要的，并且通过FeuP/FEUQ途径的信号对细胞外渗透条件做出反应，低渗透压刺激ndvA表达。
A screen for novel symbiotic mutants of the nitrogen-fixing legume symbiont Sinorhizobium meliloti uncovered a crucial role for the putative response regulator FeuP in the symbiotic infection process. Transcriptome analysis shows that FeuP controls the transcription of at least 16 genes, including ndvA, which encodes an ATP-dependent exporter of cyclic beta glucans. Loss of feuP function gives rise to traits associated with cyclic beta glucan biosynthetic defects, including poor growth and motility under hypoosmotic conditions, and the inability to invade plant tissue during the early stages of symbiotic infection. Analysis of cyclic glucans indicates that the feuP mutant is able to synthesize intracellular cyclic beta glucans, but is unable to export them. Cyclic beta glucan export can be restored to feuP mutant cells by constitutive expression of ndvA; likewise, the symbiotic phenotype of a feuP mutant is rescued by ectopic ndvA expression. We further show that the linked sensor kinase gene, feuQ, is also important for modulating ndvA transcription, and that signalling through the FeuP/FeuQ pathway is responsive to extracellular osmotic conditions, with low osmolarity stimulating ndvA expression.