A glutamine-amidotransferase-like protein modulates FixT anti-kinase activity in Sinorhizobium meliloti

被引：14

作者：

Bergès H. ^{[1
]}

Checroun C. ^{[1
]}

Guiral S. ^{[1
]}

Garnerone A.-M. ^{[1
]}

Boistard P. ^{[1
]}

Batut J. ^{[1
]}

机构：

[1] Lab. Biol. Molec. Rel. Plantes-M., UMR215 CNRS-INRA, 31326 Castanet-Tolosan Cedex

来源：

BMC Microbiology | / 1卷 / 1期

关键词：

Asparagine Synthetase; Sensor Histidine Kinase; Nitrogen Fixation Activity; Putative Open Reading Frame; Nitrogen Fixation Gene;

D O I：

10.1186/1471-2180-1-6

中图分类号：

学科分类号：

摘要：

Background: Nitrogen fixation gene expression in Sinorhizobium meliloti, the alfalfa symbiont, depends on a cascade of regulation that involves both positive and negative control. On top of the cascade, the two-component regulatory system FixLJ is activated under the microoxic conditions of the nodule. In addition, activity of the FixLJ system is inhibited by a specific anti-kinase protein, FixT. The physiological significance of this negative regulation by FixT was so far unknown. Results: We have isolated by random Tn5 mutagenesis a S. meliloti mutant strain that escapes repression by FixT. Complementation test and DNA analysis revealed that inactivation of an asparagine synthetase-like gene was responsible for the phenotype of the mutant. This gene, that was named asnO, encodes a protein homologous to glutamine-dependent asparagine synthetases. The asnO gene did not appear to affect asparagine biosynthesis and may instead serve a regulatory function in S. meliloti. We provide evidence that asnO is active during symbiosis. Conclusions: Isolation of the asnO mutant argues for the existence of a physiological regulation associated with fixT and makes it unlikely that fixT serves a mere homeostatic function in S. meliloti. Our data suggest that asnO might control activity of the FixT protein, in a way that remains to be elucidated. A proposed role for asnO might be to couple nitrogen fixation gene expression in S. meliloti to the nitrogen needs of the cells.

引用

页码：1 / 9

页数：8

共 32 条

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