T-DNA integration and expression in a monocot crop plant after induction of Agrobacterium

Schäfer, Willi; Görz, Andrea; Kahl, Günter

doi:10.1038/327529a0

Cited by 136 publications

(39 citation statements)

References 2 publications

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“…A limited range of monocots appear to be susceptible to Agrobacterium infection (8,10,11,12,14,27). Recent reports have attempted to correlate the paucity of vir inducers in monocots with their apparent nonsusceptibility (24,35), although the evidence is conflicting.…”

Section: Discussionmentioning

confidence: 99%

Ti plasmid-specified chemotaxis of Agrobacterium tumefaciens C58C1 toward vir-inducing phenolic compounds and soluble factors from monocotyledonous and dicotyledonous plants

et al. 1988

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Twelve phenolic compounds with related structures were analyzed for their ability to act as chemoattractants for Agrobacterium tumefaciens C58C1 and as inducers of the Ti plasmid virulence operons. The results divided the phenolic compounds into three groups: compounds that act as strong vir inducers and are chemoattractants for A, tumefaciens C58C0 harboring the nopaline Ti plasmid pDUB1003A31, but not the isogenic cured strain; compounds that are at best weak vir inducers and are weak chemoattractants for Ti plasmid-harboring and cured A. tumefaciens C58C'; and compounds that are vir noninducers and are also nonattractants. A strong correlation between vir-inducing ability and Ti plasmid requirement for chemotaxis is thus established. In addition, chemical structure rules for vir induction and chemotaxis are outlined. Positive chemotaxis toward root and shoot homogenates from monocotyledonous and dicotyledonous plants was observed. At low extract concentrations, chemotaxis was enhanced by the presence of Ti plasmid. The chemoattractants do not derive from intact cell walls. Lack of attraction is not responsible for the apparent block to monocot transformation by A. tumefaciens.Plant wounding is a prerequisite for crown gall tumor induction by Ti-plasmid-harboring Agrobacterium tumefaciens. The Ti plasmid virulence operons, induced by wound exudates such as acetosyringone (24,32,33), mediate T-DNA transfer to the plant cell, where neoplastic overgrowth results from its expression (19,20,23).A. tumefaciens C58C1 possesses a highly sensitive chemotaxis system, which responds to a range of sugars and amino acids (19a). For example, the chemotactic peak for sucrose occurs at 10-6 M. Thus, release of these compounds from plant roots and chemotaxis of A. tumefaciens toward them can account for the prevalence of the bacterium in the rhizosphere (15,16).The majority of chemotactic responses in A. tumefaciens appear to be chromosomally encoded (3, 19a, 25). However, chemotaxis toward acetosyringone, one of the major plant phenolic inducers, requires the presence of a Ti plasmid and occurs with a threshold sensitivity of <108 M (3), some 1,000-fold below the maximal vir-inducing concentration (32). Agrobacterium strains harboring either octopine or nopaline Ti plasmids respond at this concentration (29), indicating that chemotaxis is important in guiding virulent A. tumefaciens toward a susceptible plant (30). The Ti plasmid genes involved in this specific chemotactic response are virA and virG (29). virA and virG are also involved in mediating vir induction in response to acetosyringone (18,21,34,37). This suggests a multifunctional role for virA and virG: at low concentrations of acetosyringone they trigger chemotaxis, whereas at high concentrations vir induction is effected.To confirm and extend our previous observations, we embarked upon a survey of the vir-inducing and chemotactic properties of a variety of related phenolic compounds found in plant exudates. We present evidence indicative of a strong correlation bet...

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Section: Discussionmentioning

confidence: 99%

Ti plasmid-specified chemotaxis of Agrobacterium tumefaciens C58C1 toward vir-inducing phenolic compounds and soluble factors from monocotyledonous and dicotyledonous plants

et al. 1988

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“…Activation of the A. tumefaciens virulence genes is the key to plant transformation. Phenolic compounds (such as acetosyringone) have been identified as inducers of virulence genes in case of tobacco and rice (Stachel et al 1985, Schafer et al 1987Chan et al 1992). The results of this paper confirmed that both acetosyringone and glucose could be used as inducers of virulence genes despite the molecular bases for plant transformation are not yet well known.…”

Section: Discussionmentioning

confidence: 99%

Improved Agrobacterium-mediated genetic transformation of GNA transgenic sugarcane

et al. 2007

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Six plasmids carrying a snowdrop lectin (Galanthus nivalis agglutinin, GNA) and one of three selection markers were successfully transferred into two sugarcane cultivars (FN81-745 and Badila) via Agrobacterium-mediated transformation. Agrobacterium strains LBA4404, EHA105 and A281 that harboured a super-binary vector were used for sugarcane transformation. The use of the hygromycin (Hyg) resistance gene (hpt II), phosphinothrincin (PPT) resistance gene (bar) or G418 resistance gene (npt II) as a screenable marker facilitated the initial selection of GNA transgenic sugarcane callus with different efficiencies and helped the rapid segregation of individual transformation events. All the three selective marker genes were controlled by CaMV 35S promoter, while GNA gene was controlled by promoter of RSs-1 (rice sucrose synthase-1) or Ubi (maize ubiquitin). Factors important to successful transformation mediated by Agrobacterium tumefaciens were optimized, which included concentration of A. tumefaciens, medium composition, co-cultivated methods with plant tissue, strain virulence and different selective marker genes. An efficient protocol for sugarcane transformation mediated by A. tumefaciens was established. The GNA gene has been integrated into sugarcane genome as demonstrated by PCR and Southern dot blotting detections. The preliminary results from bioassay demonstrated a significant resistance of the transgenic sugarcane plants to woolly aphid (Ceratovacuna lanigera Zehnther) indicating thus the possibility for obtaining a transgenic sugarcane cultivar with resistance to woolly aphid.

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“…Agrobacterium tumefaciens causes crown gall tumors on a number of dicotyledonous (reviewed in references 4, 9, and 25) and some monocotyledonous (reviewed in reference 30) plants by transferring and expressing the transferred DNA (T-DNA) portion of its tumor-inducing (Ti) plasmid. The T-DNA portion is flanked by similar 25-base-pair (bp) direct repeat sequences designated as borders (3,31,48,51).…”

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confidence: 99%

Virulence genes, borders, and overdrive generate single-stranded T-DNA molecules from the A6 Ti plasmid of Agrobacterium tumefaciens

1988

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Agrobacterium tumefaciens transfers the T-DNA portion of its Ti plasmid to the nuclear genome of plant cells. Upon cocultivation of A. tumefaciens A348 with regenerating tobacco leaf protoplasts, six distinct single-stranded T-DNA molecules (T strands) were generated in addition to double-stranded T-DNA border cleavages which we have previously reported (K. Veluthambi, R.K. Jayaswal, and S.B. Gelvin, Proc. Natl. Acad. Sci. USA 84:1881-1885, 1987). The T region of an octopine-type Ti plasmid has four border repeats delimiting three T-DNA regions defined as T left (TL), T center (TC), and T right (TR). The six T strands generated upon induction corresponded to the TL, TC, TR, TL + TC, TC + TR, and TL + TC + TR regions, suggesting that the initiation and termination of T-strand synthesis can occur at each of the four borders. Most TL + TC + TR T-strand molecules corresponded to the top T-DNA strand, whereas the other five T strands corresponded to the bottom T-DNA strand. Generation of T strands required the virA, virG, and virD operons. Extra copies of vir genes, harbored on cosmids within derivatives of A. tumefaciens A348, enhanced production of T strands. The presence of right and left border repeats in their native orientation is important for the generation of full-length T strands. When a right border repeat was placed in the opposite orientation, single-stranded T-DNA molecules that corresponded to the top strand were generated. Deletion of overdrive, a sequence that flanks right border repeats and functions as a T-DNA transmission enhancer, reduced the level of T-strand generation. Induction of A. tumefaciens cells by regenerating tobacco protoplasts increased the copy number of the Ti plasmid relative to the bacterial chromosome.

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T-DNA integration and expression in a monocot crop plant after induction of Agrobacterium

Cited by 136 publications

References 2 publications

Ti plasmid-specified chemotaxis of Agrobacterium tumefaciens C58C1 toward vir-inducing phenolic compounds and soluble factors from monocotyledonous and dicotyledonous plants

Ti plasmid-specified chemotaxis of Agrobacterium tumefaciens C58C1 toward vir-inducing phenolic compounds and soluble factors from monocotyledonous and dicotyledonous plants

Improved Agrobacterium-mediated genetic transformation of GNA transgenic sugarcane

Virulence genes, borders, and overdrive generate single-stranded T-DNA molecules from the A6 Ti plasmid of Agrobacterium tumefaciens

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