Environmental conditions differentially affect vir gene induction in different Agrobacterium strains. Role of the VirA sensor protein

Turk, Stefan C. H. J.; Melchers, Leo S.; Dulk-Ras, H. den; Regensburg-Tuïnk, A.J.G.; Hooykaas, Paul J. J.

doi:10.1007/bf00016076

Cited by 64 publications

(32 citation statements)

References 35 publications

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“…the two distinct pH values which had been characterized as optimal for induction of nopaline-type or octopine-type vir genes. Indeed, previous investigators (39) had shown that the optimal pH for induction by acetosyringone of the vir genes of pTiC58 and pTiB6 was 5.8 and 5.3, respectively. No induction was noted at pH 6.8 (39).…”

Section: Resultsmentioning

confidence: 96%

Growth inhibition and loss of virulence in cultures of Agrobacterium tumefaciens treated with acetosyringone

1992

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Acetosyringone, a phenolic inducer of the virulence (vir) genes of Agrobacterium tumefaciens, inhibited the growth of the nopaline-type strains T37 and C58 incubated under acidic conditions. In the course of a 6-day incubation with acetosyringone, avirulent clones were produced in different proportions by strains T37 and C58 and also by a spontaneous variant of strain C58, denominated C58F. The proportion of avirulent clones in acetosyringone-treated cultures often exceeded 50%o for strains T37 and C58F and was of the order of 1% for strain C58. Control cultures not exposed to acetosyringone did not yield avirulent clones. Two other vir inducers, sinapinic acid and syringaldehyde, also inhibited growth and promoted accumulation of avirulent clones in cultures of strains C58F and T37. On the other hand, various acetosyringone analogs reported not to induce the vir genes did not act as growth inhibitors. All of the T37 and most of the C58F avirulent clones examined still carried a Ti plasmid. In all instances examined, avirulent clones still carrying a Ti plasmid were mutated in this plasmid. Mutants of strain C58F lacked the capacity to induce a virB::lacZ fusion in the presence of acetosyringone.The causal agent of crown gall, Agrobacterium tumefaciens, infects plant wounds where it detects the presence of specific compounds of plant origin. The virulence (vir) genes present on the Ti plasmids ofA. tumefaciens are then induced. Expression of the vir genes in the bacterium leads to the transfer to host plant cells of a particular region of the Ti plasmids, called the transferred (T-) DNA. This DNA of bacterial origin becomes stably integrated into the nuclear genome of the plant cells.

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Section: Resultsmentioning

confidence: 96%

Growth inhibition and loss of virulence in cultures of Agrobacterium tumefaciens treated with acetosyringone

1992

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“…One aspect of pilus biology that may be important for transformation is its temperature lability. Although vir gene induction is maximal at approximately 25 to 27°C (8,162,323), the pilus of some, but not all, Agrobacterium strains is most stable at lower temperatures (approximately 18 to 20°C) (18,105,188). Early experiments by Riker indicated a temperature effect on transformation (268).…”

Section: How Is T-dna Transferred From Agrobacteriummentioning

confidence: 99%

Agrobacterium -Mediated Plant Transformation: the Biology behind the “Gene-Jockeying” Tool

Gelvin

2003

Microbiol Mol Biol Rev

1,136

687

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SUMMARY Agrobacterium tumefaciens and related Agrobacterium species have been known as plant pathogens since the beginning of the 20th century. However, only in the past two decades has the ability of Agrobacterium to transfer DNA to plant cells been harnessed for the purposes of plant genetic engineering. Since the initial reports in the early 1980s using Agrobacterium to generate transgenic plants, scientists have attempted to improve this “natural genetic engineer” for biotechnology purposes. Some of these modifications have resulted in extending the host range of the bacterium to economically important crop species. However, in most instances, major improvements involved alterations in plant tissue culture transformation and regeneration conditions rather than manipulation of bacterial or host genes. Agrobacterium-mediated plant transformation is a highly complex and evolved process involving genetic determinants of both the bacterium and the host plant cell. In this article, I review some of the basic biology concerned with Agrobacterium-mediated genetic transformation. Knowledge of fundamental biological principles embracing both the host and the pathogen have been and will continue to be key to extending the utility of Agrobacterium for genetic engineering purposes.

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“…However, those studies were done in vitro after pH adjustment of the extracts and so may not reflect the situation in planta. This is especially relevant since Turk et al (41) have shown that octopine-and nopaline-type VirA proteins differ in their pH requirements for optimal vir induction. Thus, it may be that cereal sap is more compatible with the functioning of nopaline-type VirA than octopine-type VirA.…”

Section: Discussionmentioning

confidence: 99%

VirA, the plant-signal receptor, is responsible for the Ti plasmid-specific transfer of DNA to maize by Agrobacterium.

Raineri

Boulton

Davies

et al. 1993

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

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Agrobacteria exhibit marked Ti (tumorinducing)/Ri (root-inducing) plasmid specificity in their interaction with the Gramineae. In this study, we have used the technique of "agroinfection," in which Agrobacterium-mediated delivery of viral genomes into plants is detected by the development of viral disease symptoms, to identify the region of the Ti plasmid which is responsible for the major differences seen in the ability of nopaline-vs. plants (4, 5). However, more recent work reported that certain monocotyledonous plants (monocots) are also susceptible (6-9). Furthermore, although maize and other graminaceous monocots have remained refractory to tumor formation, the agroinfection technique used to study the transfer of viral DNA to dicots (10, 11) has confirmed that Agrobacterium is able to transfer DNA to cereal plants (12)(13)(14)(15)(16)(17). Agroinfection is mediated through the same vir gene pathway as is required for tumor formation in dicots (18).This technique provides a very sensitive assay for Agrobacterium-mediated DNA transfer, as the viral sequences escape from the T-DNA and are amplified as the virus replicates and spreads systemically. DNA transfer is thus detected by the formation of disease symptoms.The ability to agroinfect maize was found to be Ti plasmidspecific (13, 16): octopine-type strains either were unable, or only weakly able (<5%), to transfer maize streak virus (MSV) DNA, while nopaline-type strains infected 80-100%o of the inoculated plants. Agropine-and mannopine-type strains of A. rhizogenes also efficiently agroinfected maize. With appropriate viral DNAs as markers, similar results were obtained for other members of the Gramineae (14,15,17). In contrast, Ti plasmid specificity is not typical of agroinfection-dicot interactions (10, 11).A "disarmed" (T-DNA-less) nopaline strain agroinfected maize as efficiently as the wild type (13). Therefore, Ti plasmid specificity cannot be due to differences in phytohormone production specified by the T-DNA. One explanation for the inability of octopine-type strains to agroinfect maize and other graminaceous monocots is that octopine-type Ti plasmids lack an essential function present in nopaline-, agropine-, and mannopine-type Ti/Ri plasmids. Alternatively, octopine-type Ti plasmids might express a counteractive function.We have used the agroinfection system to characterize the Ti plasmid requirements for transfer of MSV DNA to maize. We observed that a DNA fragment containing the nopalinetype virA locus complemented octopine-type Ti plasmids to high levels of agroinfection. Furthermore, whereas preinduction of octopine-type strains does not promote maize agroinfection, octopine-type virA mutant strains, which express vir genes at high levels in the absence of the inducing compound acetosyringone, efficiently transferred MSV DNA to maize. We discuss here the implications of these observations and possible causes. MATERIALS AND METHODSBacterial Strains, Plasmids, and Media. The MSV-containing binary vectors and other plasmids used in...

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Environmental conditions differentially affect vir gene induction in different Agrobacterium strains. Role of the VirA sensor protein

Cited by 64 publications

References 35 publications

Growth inhibition and loss of virulence in cultures of Agrobacterium tumefaciens treated with acetosyringone

Growth inhibition and loss of virulence in cultures of Agrobacterium tumefaciens treated with acetosyringone

Agrobacterium -Mediated Plant Transformation: the Biology behind the “Gene-Jockeying” Tool

VirA, the plant-signal receptor, is responsible for the Ti plasmid-specific transfer of DNA to maize by Agrobacterium.

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