title: The ColRS system of Xanthomonas oryzae pv. oryzae is required for virulence and growth in iron-limiting conditions.
abstract: Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice, produces siderophores only under iron-limiting conditions. We screened 15 400 mTn5-induced mutants of X. oryzae pv. oryzae and isolated 27 mutants that produced siderophores even under iron-replete conditions. We found that the mTn5 insertions in 25 of these mutants were in or close to six genes. Mutants with insertions in five of these genes [colS, XOO1806 (a conserved hypothetical protein), acnB, prpR and prpB] exhibited a deficiency for growth on iron-limiting medium and a decrease in virulence. Insertions in a sixth gene, XOO0007 (a conserved hypothetical protein), were found to affect the ability to grow on iron-limiting medium, but did not affect the virulence. Targeted gene disruptants for colR (encoding the predicted cognate regulatory protein for ColS) also exhibited a deficiency for growth on iron-limiting medium and a decrease in virulence. colR and colS mutants were defective in the elicitation of hypersensitive response symptoms on the nonhost tomato. In addition, colR and colS mutants induced a rice basal defence response, suggesting that they are compromised in the suppression of host innate immunity. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that a functional ColRS system is required for the optimal expression of several genes encoding components of the type 3 secretion system (T3SS) of X. oryzae pv. oryzae. Our results demonstrate the role of several novel genes, including colR/colS, in the promotion of growth on iron-limiting medium and the virulence of X. oryzae pv. oryzae.
authors.affiliation: Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad-500 007, Andhra Pradesh, India.
authors.forename: Sujatha
authors.initials: S
authors.lastname: Subramoni
authors.forename: Alok
authors.initials: A
authors.lastname: Pandey
authors.forename: M R
authors.initials: MR
authors.lastname: Vishnu Priya
authors.forename: Hitendra Kumar
authors.initials: HK
authors.lastname: Patel
authors.forename: Ramesh V
authors.initials: RV
authors.lastname: Sonti
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial / Q000235:genetics; D007501:Iron / Q000494:pharmacology*; D018551:Solanum lycopersicum / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D010641:Phenotype; D017422:Sequence Analysis, DNA; D017262:Siderophores / Q000378:metabolism; D014774:Virulence / Q000187:drug effects / Q000235:genetics; D014974:Xanthomonas / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D017262:Siderophores; D007501:Iron