title: Evaluation of the virulence of Xanthomonas campestris pv. campestris mutant strains lacking functional genes in the OxyR regulon.
abstract: Xanthomonas campestris pv. campestris causes black rot in cruciferous crops. Hydrogen peroxide (H(2)O(2)) production and accumulation is an important initial response in plant defense against invading microbes. The role of genes involved in the bacterial H(2)O(2) protection system in pathogenicity was evaluated. Mutants of katA (encoding a monofunctional catalase) and, to a lesser extent, katG (encoding a catalase-peroxidase) and oxyR (encoding a H(2)O(2) sensor and a transcription regulator), are hypersensitive to H(2)O(2) treatments that mimic the plant H(2)O(2) burst. These data correlate with the results of pathogenicity testing that show katA, katG, and oxyR mutants are avirulent on a compatible plant. Moreover, exposure to H(2)O(2) (1, 2, and 4 mM) highly induces the expression of genes in the OxyR regulon, including katA, katG, and ahpC. The avirulent phenotype of the oxyR mutant is partly because of its inability to mount an adaptive response upon exposure to an H(2)O(2) burst. Our data provide insights into important roles of a transcription regulator and other genes involved in peroxide stress protection in the virulence of X. campestris pv. campestris.
authors.affiliation: Laboratory of Biotechnology, Chulabhorn Research Institute, Vibhavadee-Rangsit Rd., Lak Si, Bangkok, Thailand.
authors.forename: Nisanart
authors.initials: N
authors.lastname: Charoenlap
authors.forename: Sarinya
authors.initials: S
authors.lastname: Buranajitpakorn
authors.forename: Jintana
authors.initials: J
authors.lastname: Duang-Nkern
authors.forename: Poommaree
authors.initials: P
authors.lastname: Namchaiw
authors.forename: Paiboon
authors.initials: P
authors.lastname: Vattanaviboon
authors.forename: Skorn
authors.initials: S
authors.lastname: Mongkolsuk
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000633:toxicity*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D009195:Peroxidase / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology*; D018085:Regulon; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014774:Virulence; D016959:Xanthomonas campestris / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D050505:Mutant Proteins; D014157:Transcription Factors; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase