RirA is the iron response regulator of the rhizobactin 1021 biosynthesis and transport genes in<i>Sinorhizobium meliloti</i>2011

Viguier, Caroline; Cuív, Páraic Ó; Clarke, Paul; O’Connell, Michael P.

doi:10.1016/j.femsle.2005.04.012

Cited by 51 publications

(61 citation statements)

References 28 publications

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“…Several studies have clearly shown that RirA evolved to carry out typical Fur functions in controlling iron uptake systems (29,30). The inactivation of rirA led to the deregulation of iron uptake, which typically was indicated by the overexpression of siderophore synthesis and transport genes.…”

Section: Resultsmentioning

confidence: 99%

Roles of Agrobacterium tumefaciens RirA in Iron Regulation, Oxidative Stress Response, and Virulence

et al. 2009

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The analysis of genetics and physiological functions of Agrobacterium tumefaciens RirA (rhizobial iron regulator) has shown that it is a transcription regulator and a repressor of iron uptake systems. The rirA mutant strain (NTLrirA) overproduced siderophores and exhibited a highly constitutive expression of genes involved in iron uptake (fhuA, irp6A, and fbpA) compared to that of the wild-type strain (NTL4). The deregulation in the iron control of iron uptake in NTLrirA led to iron overload in the cell, which was supported by the observation that the NTLrirA mutant was more sensitive than wild-type NTL4 to an iron-activated antibiotic, streptonigrin. The NTLrirA mutant was more sensitive than the parental strain to oxidants, including hydrogen peroxide, organic hydroperoxide, and a superoxide generator, menadione. However, the addition of an iron chelator, 2,2-dipyridyl, reversed the mutant hypersensitivity to H 2 O 2 and organic hydroperoxide, indicating the role of iron in peroxide toxicity. Meanwhile, the reduced level of superoxide dismutase (SodBIII) was partly responsible for the menadione-sensitive phenotype of the NTLrirA mutant. The NTLrirA mutant showed a defect in tumorigenesis on tobacco leaves, which likely resulted from the increased sensitivity of NTLrirA to oxidants and the decreased ability of NTLrirA to induce virulence genes (virB and virE). These data demonstrated that RirA is important for A. tumefaciens during plant-pathogen interactions.

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Section: Resultsmentioning

confidence: 99%

Roles of Agrobacterium tumefaciens RirA in Iron Regulation, Oxidative Stress Response, and Virulence

et al. 2009

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“…The sole B. japonicum target gene for which this regulatory function of Fur has been well documented is the irr gene (13), and only indirect evidence suggests Fur-dependent repression also at the hemA (25) and the fegA genes (34). This situation is reminiscent to that in R. leguminosarum and Sinorhizobium meliloti, where RirA, and not Fur, is the general iron regulator (59,62).…”

Section: Vol 188 2006 Iron-controlled Gene Expression In B Japonicmentioning

confidence: 99%

The Iron Control Element, Acting in Positive and Negative Control of Iron-RegulatedBradyrhizobium japonicumGenes, Is a Target for the Irr Protein

Rudolph¹,

Semini²,

Hauser³

et al. 2006

J Bacteriol

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Bradyrhizobium japonicum, the nitrogen-fixing soybean symbiont, possesses a heme uptake system encoded by the gene cluster hmuVUT-hmuR-exbBD-tonB. Transcription of the divergently oriented hmuT and hmuR genes was previously found to be induced by iron limitation and to depend on a 21-bp promoter-upstream iron control element (ICE). Here, we show by deletion analysis that the full-length ICE is needed for this type of positive control. Additional genes associated with ICE-like motifs were identified in the B. japonicum genome, of which bll6680 and blr7895 code for bacterioferritin and rubrerythrin homologs, respectively. Transcription start site mapping revealed that their ICEs directly overlap with either the ؊10 promoter region or the transcription initiation site, suggesting an involvement of the ICE in negative control of both genes. Consistent with this inference was the observed downregulation of both genes under iron limitation, which in the case of bll6680 was shown to require an intact ICE motif. Using a yeast one-hybrid system, we demonstrated in vivo interaction of the iron response regulator (Irr) with all three ICEs. Moreover, specific in vitro binding of purified Irr protein to the ICE motifs of bll6680 and blr7895 was shown in electrophoretic mobility shift experiments. A genome-wide survey for iron-regulated genes with a custom-made Affymetrix gene chip revealed 17 genes to be induced and 68 to be repressed under iron-replete conditions. Remarkably, ICE-like motifs are associated with a large subset of those B. japonicum genes. We propose the ICE as an important cis-acting element in B. japonicum which represents the DNA-binding site for the Irr protein and, depending on its location within promoter regions, is involved in positive or negative control of the associated iron-regulated genes.

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“…The iron response regulator (Irr) is found in most Alphaproteobacteria species, and many within this taxonomic group contain RirA as well (6,23,24). Irr has been studied most intensely in Bradyrhizobium japonicum, where it was initially identified in a screen for mutants defective in the control of heme biosynthesis (11).…”

mentioning

confidence: 99%

TheBradyrhizobium japonicumIrr Protein Is a Transcriptional Repressor with High-Affinity DNA-Binding Activity

2008

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RirA is the iron response regulator of the rhizobactin 1021 biosynthesis and transport genes inSinorhizobium meliloti2011

Cited by 51 publications

References 28 publications

Roles of Agrobacterium tumefaciens RirA in Iron Regulation, Oxidative Stress Response, and Virulence

Roles of Agrobacterium tumefaciens RirA in Iron Regulation, Oxidative Stress Response, and Virulence

The Iron Control Element, Acting in Positive and Negative Control of Iron-RegulatedBradyrhizobium japonicumGenes, Is a Target for the Irr Protein

TheBradyrhizobium japonicumIrr Protein Is a Transcriptional Repressor with High-Affinity DNA-Binding Activity

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