title: The Tzs protein and exogenous cytokinin affect virulence gene expression and bacterial growth of Agrobacterium tumefaciens.
abstract: The soil phytopathogen Agrobacterium tumefaciens causes crown gall disease in a wide range of plant species. The neoplastic growth at the infection sites is caused by transferring, integrating, and expressing transfer DNA (T-DNA) from A. tumefaciens into plant cells. A trans-zeatin synthesizing (tzs) gene is located in the nopaline-type tumor-inducing plasmid and causes trans-zeatin production in A. tumefaciens. Similar to known virulence (Vir) proteins that are induced by the vir gene inducer acetosyringone (AS) at acidic pH 5.5, Tzs protein is highly induced by AS under this growth condition but also constitutively expressed and moderately upregulated by AS at neutral pH 7.0. We found that the promoter activities and protein levels of several AS-induced vir genes increased in the tzs deletion mutant, a mutant with decreased tumorigenesis and transient transformation efficiencies, in Arabidopsis roots. During AS induction and infection of Arabidopsis roots, the tzs deletion mutant conferred impaired growth, which could be rescued by genetic complementation and supplementing exogenous cytokinin. Exogenous cytokinin also repressed vir promoter activities and Vir protein accumulation in both the wild-type and tzs mutant bacteria with AS induction. Thus, the tzs gene or its product, cytokinin, may be involved in regulating AS-induced vir gene expression and, therefore, affect bacterial growth and virulence during A. tumefaciens infection.
authors.affiliation: Department of Life Sciences, National Chung-Hsing University, Taichung, Taiwan, 402. hauhsuan@dragon.nchu.edu.tw
authors.forename: Hau-Hsuan
authors.initials: HH
authors.lastname: Hwang
authors.forename: Fong-Jhih
authors.initials: FJ
authors.lastname: Yang
authors.forename: Tun-Fang
authors.initials: TF
authors.lastname: Cheng
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Ying-Ling
authors.initials: YL
authors.lastname: Lee
authors.forename: Yun-Long
authors.initials: YL
authors.lastname: Tsai
authors.forename: Erh-Min
authors.initials: EM
authors.lastname: Lai
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D017360:Arabidopsis / Q000382:microbiology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism / Q000494:pharmacology; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology*; D018517:Plant Roots / Q000382:microbiology; D010941:Plant Tumors / Q000382:microbiology*; D010957:Plasmids / Q000235:genetics; D017384:Sequence Deletion; D015854:Up-Regulation; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D015026:Zeatin / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000098:Acetophenones; D001426:Bacterial Proteins; D003583:Cytokinins; D010937:Plant Growth Regulators; D037521:Virulence Factors; D015026:Zeatin; C051667:acetosyringone