title: GacA directly regulates expression of several virulence genes in Pseudomonas syringae pv. tabaci 11528.
abstract: A two-component system comprising GacS and GacA affects a large number of traits in many Gram-negative bacteria. However, the signals to which GacS responds, the regulation mechanism for GacA expression, and the genes GacA controls are not yet clear. In this study, several phenotypic tests and tobacco-leaf pathogenicity assays were conducted using a gacA deletion mutant strain (BL473) of Pseudomonas syringae pv. tabaci 11528. To determine the regulation mechanism for gacA gene expression and to identify GacA-regulated genes, we conducted quantitative RT-PCR and electrophoretic mobility shift assay (EMSA) experiments. The results indicated that virulence traits related to the pathogenesis of P. syringae pv. tabaci 11528 are regulated coordinately by GacA and iron availability. They also revealed that several systems coordinately regulate gacA gene expression in response to iron concentration and bacterial cell density and that GacA and iron together control the expression of several virulence genes. EMSA results provided genetic and molecular evidence for direct control of virulence genes by GacA.
authors.affiliation: Department of Microbiology, College of Natural Science, Pusan National University, Busan 609-735, Republic of Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Cha
authors.forename: Dong Gwang
authors.initials: DG
authors.lastname: Lee
authors.forename: Jun Seung
authors.initials: JS
authors.lastname: Lee
authors.forename: Jeong-Il
authors.initials: JI
authors.lastname: Oh
authors.forename: Hyung Suk
authors.initials: HS
authors.lastname: Baik
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D056426:Genetic Loci; D007501:Iron / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D011401:Promoter Regions, Genetic; D044224:Pseudomonas syringae / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D014026:Nicotiana / Q000382:microbiology*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D007501:Iron