title: RpoH2 sigma factor controls the photooxidative stress response in a non-photosynthetic rhizobacterium, Azospirillum brasilense Sp7.
abstract: Bacteria belonging to the Alphaproteobacteria normally harbour multiple copies of the heat shock sigma factor (known as σ(32), σ(H) or RpoH). Azospirillum brasilense, a non-photosynthetic rhizobacterium, harbours five copies of rpoH genes, one of which is an rpoH2 homologue. The genes around the rpoH2 locus in A. brasilense show synteny with that found in rhizobia. The rpoH2 of A. brasilense was able to complement the temperature-sensitive phenotype of the Escherichia coli rpoH mutant. Inactivation of rpoH2 in A. brasilense results in increased sensitivity to methylene blue and to triphenyl tetrazolium chloride (TTC). Exposure of A. brasilense to TTC and the singlet oxygen-generating agent methylene blue induced several-fold higher expression of rpoH2. Comparison of the proteome of A. brasilense with its rpoH2 deletion mutant and with an A. brasilense strain overexpressing rpoH2 revealed chaperone GroEL, elongation factors (Ef-Tu and EF-G), peptidyl prolyl isomerase, and peptide methionine sulfoxide reductase as the major proteins whose expression was controlled by RpoH2. Here, we show that the RpoH2 sigma factor-controlled photooxidative stress response in A. brasilense is similar to that in the photosynthetic bacterium Rhodobacter sphaeroides, but that RpoH2 is not involved in the detoxification of methylglyoxal in A. brasilense.
authors.affiliation: Laboratory of Bacterial Genetics, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi-221005, India.
authors.forename: Santosh
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Laboratory of Bacterial Genetics, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi-221005, India.
authors.forename: Ashutosh Kumar
authors.initials: AK
authors.lastname: Rai
authors.affiliation: Laboratory of Bacterial Genetics, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi-221005, India.
authors.forename: Mukti Nath
authors.initials: MN
authors.lastname: Mishra
authors.affiliation: Laboratory of Bacterial Genetics, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi-221005, India.
authors.forename: Mansi
authors.initials: M
authors.lastname: Shukla
authors.affiliation: National Botanical Research Institute, Rana Pratap Marg, Lucknow-226001, India.
authors.forename: Pradhyumna Kumar
authors.initials: PK
authors.lastname: Singh
authors.affiliation: Laboratory of Bacterial Genetics, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi-221005, India.
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: Tripathi
mesh_terms: D015806:Azospirillum brasilense / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008751:Methylene Blue / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress; D020543:Proteome / Q000032:analysis; D012242:Rhodobacter sphaeroides / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological; D013778:Tetrazolium Salts / Q000378:metabolism
chemical_list: D006360:Heat-Shock Proteins; D016877:Oxidants; D020543:Proteome; D012808:Sigma Factor; D013778:Tetrazolium Salts; C069774:heat-shock sigma factor 32; C009591:triphenyltetrazolium; D008751:Methylene Blue