Inducible Expression of Cytokinin Biosynthesis in<i>Agrobacterium tumefaciens</i>by Plant Phenolics

Gk, Powell; Ng, Hommes; Kuo, Jen-Tsai; La, Castle; Ro, Morris

doi:10.1094/mpmi-1-235

Cited by 45 publications

(35 citation statements)

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“…Interestingly, the VirB5 protein interacts with the cytokinin biosynthetic enzyme Tzs (trans-zeatin synthesizing) protein in yeast and in vitro (Aly et al, 2008). The tzs gene in the nopaline strains of A. tumefaciens shares significant homology with the ipt gene, is located outside the T-DNA region and is not incorporated into the host plant genome during infection (Akiyoshi et al, 1985(Akiyoshi et al, , 1987Beaty et al, 1986;Powell et al, 1988). The loss of Tzs protein expression and trans-zeatin secretion by the tzs mutants correlates with reduced stable and transient transformation efficiencies on Arabidopsis roots, suggesting the Tzs, by synthesizing trans-zeatin at early stage(s) of the infection process, modulates plant transformation efficiency by A. tumefaciens (Hwang et al, 2010;Hwang et al, 2013b).…”

Section: Transport Of T-dna and Virulence Proteins Via Type IV Secretmentioning

confidence: 99%

Agrobacterium-Mediated Plant Transformation: Biology and Applications

Hwang

Lai

2017

The Arabidopsis Book

198

142

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Section: Transport Of T-dna and Virulence Proteins Via Type IV Secretmentioning

confidence: 99%

Agrobacterium-Mediated Plant Transformation: Biology and Applications

Hwang

Lai

2017

The Arabidopsis Book

198

142

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“…The Tzs gene is located in the virulence region of nopaline-type Ti-plasmids (16). Tzs stimulates T-DNA transfer efficiency (16,17), whereas Tmr, which is encoded in the T-DNA region, induces tumorigenesis in host plant cells (10,18).…”

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confidence: 99%

Structural insight into the reaction mechanism and evolution of cytokinin biosynthesis

Sugawara

Ueda

Kojima

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The phytohormone cytokinin regulates plant growth and development. This hormone is also synthesized by some phytopathogenic bacteria, such as Agrobacterium tumefaciens, and is as a key factor in the formation of plant tumors. The rate-limiting step of cytokinin biosynthesis is catalyzed by adenosine phosphateisopentenyltransferase (IPT). Agrobacterium IPT has a unique substrate specificity that enables it to increase trans-zeatin production by recruiting a metabolic intermediate of the host plant's biosynthetic pathway. Here, we show the crystal structures of Tzs, an IPT from A. tumefaciens, complexed with AMP and a prenyl-donor analogue, dimethylallyl S-thiodiphosphate. The structures reveal that the carbon-nitrogen-based prenylation proceeds by the SN2-reaction mechanism. Site-directed mutagenesis was used to determine the amino acid residues, Asp-173 and His-214, which are responsible for differences in prenyl-donor substrate specificity between plant and bacterial IPTs. IPT and the p loop-containing nucleoside triphosphate hydrolases likely evolved from a common ancestral protein. Despite structural similarities, IPT has evolved a distinct role in which the p loop transfers a prenyl moiety in cytokinin biosynthesis.Agrobacterium tumefaciens ͉ crystal structure ͉ isopentenyltransferase ͉ trans-zeatin ͉ p loop-containing nucleoside triphosphate hydrolases

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“…Cytokinin biosynthesis in A. tumefaciens strain C58 is catalyzed by the enzyme DMA transferase which condenses dimethylallylpyrophosphate and 5'AMP to give the 5' phosphate of isopentenyladenosine (iPMP) (2). Subsequent hydroxylation of iPMP to ZR 5'-monophosphate, dephosphorylation and deribosylation yield Z, which is excreted into the medium at about 0.05 Mm in late log phase cultures (18). Smaller amounts of iP are also produced (20).…”

Section: Resultsmentioning

confidence: 99%

“…Starter cultures were grown overnight in the presence or absence of acetosyringone. Inasmuch as it had been determined that cytokinin production by acetosyringone-induced cultures peaked in stationary phase (18), [3H]adenine (10 iCi) was added at late log phase (A650 = 0.3-0.6), and cultures were harvested after 6.5 h.…”

Section: Strains and Constructsmentioning

confidence: 99%

Rapid Identification of Cytokinins by an Immunological Method

Morris

Jameson²,

Laloue³

et al. 1991

Plant Physiol.

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A method for rapid identification of bacterial cytokinins has been developed in which cultures are fed [3H]adenine, the cytokinins (including 3H-labeled cytokinins) are isolated by immunoaffinity chromatography, and analyzed by HPLC with on-line scintillation counting. Analysis of Agrobacterium tumefaciens strains showed that some produced primarily trans-zeatin, whereas others produced primarily trans-zeatin riboside. Pseudomonas syringae pv savastanoi produced mixtures of transzeatin, dihydrozeatin, 1"-methyl-trans-zeatin riboside, and other unknown cytokinin-like substances. Corynebacterium fascians, produced cis-zeatin, isopentenyladenine and isopentenyladenosine. The technique is designed for qualitative rather than quantitative studies and allows ready identification of bacterial cyto- 'Abbreviations: RIA, radioimmunoassay; "MeZR, 1 "-methyl trans-zeatin riboside; cZ, cis-zeatin; cZR, cis-zeatin riboside; DZ, dihydrozeatin; DZR, dihydrozeatin riboside; iP, isopentenyladenine; iPA, isopentenyladenosine; Z, trans-zeatin; ZR, trans-zeatin riboside.Unfortunately, direct analysis of phytohormones in unfractionated plant extracts by RIA or ELISA can lead to erroneous results. In some cases, crude extracts may contain compounds which cause nonspecific interference; their presence leads to generation of false positives. For example, Cohen et al. (6) showed that ELISA ofIAA in even semipurified plant samples led to high estimates of the IAA content. As successively more pure samples were analyzed, the apparent IAA values approached those determined by rigorous mass spectrometric analysis. Nonspecific interference is, however, not the only problem. When several cross-reacting phytohormone species are present, a composite result will be obtained. A case in point is the analysis of bacterially produced cytokinins. The primary cytokinin produced by Agrobacterium tumefaciens strain C58 has been shown to be zeatin (9). Small amounts of iP are also present, but not in sufficient quantity to interfere with zeatin-specific RIA of supernatants (20). Zeatin determination by ELISA or RIA is therefore likely to give reasonably accurate results. The same is not true for Pseudomonas syringae pv savastanoi strains. Some strains secrete Z, ZR, and 1 "MeZR and, late in stationary phase, these are present in the medium in approximately equal quantities (14). Since the relative cross reactivities of Z, ZR and 1 "MeZR with anti-ZR antibody are approximately 10:50:1 (unpublished data), assays ofunfractionated supernatants will not give meaningful data. For most plant samples, where several cytokinins are usually present, the same considerations apply.The problem can be alleviated by combining immunoaffinity chromatography, to purify the cytokinins from nonspecific interfering substances (13), with HPLC to separate the individual components. RIA or ELISA can then be used to detect each cytokinin in the appropriate HPLC fraction (7,12

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Inducible Expression of Cytokinin Biosynthesis inAgrobacterium tumefaciensby Plant Phenolics

Cited by 45 publications

References 0 publications

Agrobacterium-Mediated Plant Transformation: Biology and Applications

Agrobacterium-Mediated Plant Transformation: Biology and Applications

Structural insight into the reaction mechanism and evolution of cytokinin biosynthesis

Rapid Identification of Cytokinins by an Immunological Method

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