title: Agrobacterium-produced and exogenous cytokinin-modulated Agrobacterium-mediated plant transformation.
abstract: Agrobacterium tumefaciens is a plant pathogenic bacterium that causes neoplastic growths, called 'crown gall', via the transfer and integration of transferred DNA (T-DNA) from the bacterium into the plant genome. We characterized an acetosyringone (AS)-induced tumour-inducing (Ti) plasmid gene, tzs (trans-zeatin synthesizing), that is responsible for the synthesis of the plant hormone cytokinin in nopaline-type A. tumefaciens strains. The loss of Tzs protein expression and trans-zeatin secretions by the tzs frameshift (tzs-fs) mutant is associated with reduced tumorigenesis efficiency on white radish stems and reduced transformation efficiencies on Arabidopsis roots. Complementation of the tzs-fs mutant with a wild-type tzs gene restored wild-type levels of trans-zeatin secretions and transformation efficiencies. Exogenous application of cytokinin during infection increased the transient transformation efficiency of Arabidopsis roots infected by strains lacking Tzs, which suggests that the lower transformation efficiency resulted from the lack of Agrobacterium-produced cytokinin. Interestingly, although the tzs-fs mutant displayed reduced tumorigenesis efficiency on several tested plants, the loss of Tzs enhanced tumorigenesis efficiencies on green pepper and cowpea. These data strongly suggest that Tzs, by synthesizing trans-zeatin at early stage(s) of the infection process, modulates plant transformation efficiency by A. tumefaciens.
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan. hauhsuan@dragon.nchu.edu.tw
authors.forename: Hau-Hsuan
authors.initials: HH
authors.lastname: Hwang
authors.forename: Ming-Hsuan
authors.initials: MH
authors.lastname: Wang
authors.forename: Ying-Ling
authors.initials: YL
authors.lastname: Lee
authors.forename: Yun-Long
authors.initials: YL
authors.lastname: Tsai
authors.forename: Yi-Ho
authors.initials: YH
authors.lastname: Li
authors.forename: Fong-Jhih
authors.initials: FJ
authors.lastname: Yang
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Liao
authors.forename: Shao-Kai
authors.initials: SK
authors.lastname: Lin
authors.forename: Erh-Min
authors.initials: EM
authors.lastname: Lai
mesh_terms: D016960:Agrobacterium tumefaciens / Q000187:drug effects* / Q000235:genetics* / Q000472:pathogenicity; D017360:Arabidopsis / Q000187:drug effects / Q000382:microbiology; D003583:Cytokinins / Q000096:biosynthesis* / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D009154:Mutation / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000382:microbiology; D035281:Plant Tubers / Q000187:drug effects / Q000382:microbiology; D036741:Plant Tumor-Inducing Plasmids / Q000235:genetics; D010941:Plant Tumors / Q000382:microbiology; D031224:Raphanus / Q000187:drug effects / Q000382:microbiology; D013045:Species Specificity; D014170:Transformation, Genetic / Q000187:drug effects*; D014774:Virulence / Q000187:drug effects; D015026:Zeatin / Q000378:metabolism
chemical_list: D003583:Cytokinins; D004269:DNA, Bacterial; C036483:T-DNA; D015026:Zeatin