PMID:19168612

Citation	Ngok-Ngam, P, Ruangkiattikul, N, Mahavihakanont, A, Virgem, SS, Sukchawalit, R and Mongkolsuk, S (2009) Roles of Agrobacterium tumefaciens RirA in iron regulation, oxidative stress response, and virulence. J. Bacteriol. 191:2083-90
Abstract	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.
Links	PubMed PMC2655498 Online version:10.1128/JB.01380-08
Keywords	Agrobacterium tumefaciens/genetics; Agrobacterium tumefaciens/metabolism; Agrobacterium tumefaciens/pathogenicity; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Gene Expression Regulation, Bacterial; Hydrogen Peroxide/metabolism; Iron/metabolism; Iron-Regulatory Proteins/genetics; Iron-Regulatory Proteins/metabolism; Oxidative Stress; Plant Tumors/microbiology; Superoxide Dismutase/genetics; Superoxide Dismutase/metabolism; Tobacco/microbiology; Virulence
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
AGRT5:A9CKK6		GO:0045893: transcription regulator activity	ECO:0000315:		F		Figure 4 shows that the gene is not expressed, and Figure 3 shows what happens when it is not expressed.	complete

References

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