Promoters of<i>Agrobacterium tumefaciens</i>Ti-plasmid virulence genes

Das, Anath Bandhu; Stachel, Scott E.; Ebert, Paul R.; Allenza, P.; Montoya, Alice L.; Nester, Eugene W.

doi:10.1093/nar/14.3.1355

Cited by 88 publications

(53 citation statements)

References 22 publications

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“…Expression of virG in response to acidic pH does not require VirG protein or any other Ti plasmid-encoded function, indicating that the gene regulating P2 must be located on the chromosome (63). The sequence of P2 is different from those of other identified A. tumefaciens promoters (9), suggesting that transcription of P2 may require an alternative sigma factor.…”

Section: Resultsmentioning

confidence: 95%

“…Although P2 was originally thought to be expressed constitutively (53), deletions which remove this promoter abolish induction of virG by acidic growth media (61), suggesting that P2 may be transcriptionally induced by this stimulus. In addition, the sequence of P2 does not resemble those of the other vir promoters (9) but is very similar at its -10 region to the consensus sequence of Escherichia coli heat shock promoters (8,61).…”

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confidence: 92%

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The Agrobacterium tumefaciens vir gene transcriptional activator virG is transcriptionally induced by acid pH and other stress stimuli

Mantis

Winans

1992

J Bacteriol

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A set of Agrobacterium tumefaciens operons required for pathogenesis is coordinately induced during plant infection by the VirA and VirG proteins. The intracellular concentration of VirG increases in response to acidic media, and this response was proposed to be regulated at the level of transcription at a promoter (P2) that resembles the Escherichia coli heat shock promoters. To test this hypothesis, we first constructed a virG-lacZ transcriptional fusion. A strain containing this fusion had higher levels of I-galactosidase activity in acidic media than in media at neutral pH. Second, primer extension analysis of virG indicated that acidic media stimulated the transcription of this promoter. To determine whether P2 is a member of a heat shock-like regulon in A. tumefaciens, five agents that induce E. coli heat shock genes were tested for their abilities to induce a P2-lacZ fusion in A. tumefaciens. P2 was most strongly induced by low pH, was moderately stimulated by CdCI2 or mitomycin C, and was slightly induced by alkaline pH or ethanol. Heat shock or growth at high temperature did not cause detectable induction of P2 as measured by I-galactosidase activity and primer extension analysis. Induction by these treatments did not require any Ti plasmid-encoded function or the chromosomally encoded RecA protein. We also pulse-labeled cellular proteins after a shift to low pH and detected several proteins whose synthesis was induced by these conditions. We conclude that P2 is primarily induced by acid pH and secondarily by certain other stimuli, each of which is stressful to cell growth. This stress induction is at least partly independent of the heat shock and SOS responses.Establishment of crown gall tumors on plant hosts by Agrobacterium tumefaciens requires the recognition of a plant wound susceptible to infection, transfer of a discrete segment of DNA (T-DNA) to the plant cell nucleus, and integration of T-DNA into the plant genome (for reviews, see references 2, 12, 23, 43, and 66). The genes required for T-DNA transfer (vir genes) are located on a large plasmid, called the Ti plasmid. The vir genes are transcriptionally induced in response to a family of phenolic compounds produced by wounded plant cells (50, 51). Induction also requires acidic growth medium (52) and is potentiated by certain monosaccharides (3,47).Two members of the vir regulon, virA and virG, are required for vir gene induction (44,53,63) and encode proteins that are members of the family of bacterial twocomponent regulatory systems (28, 37, 42, 62). For some vir promoters, VirA and VirG are the only known regulatory proteins (34, 64), while the virC and virD promoters are also controlled by a repressor encoded by the chromosomal ros gene (5, 7). VirA is a transmembrane protein kinase that can phosphorylate itself and VirG (19,21,22,36). VirG specifically binds cis-acting regulatory sequences involved in transcriptional activation of the virulence genes (22,40,41). Recent evidence indicates that vir expression is rate limited by the pool siz...

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Section: Resultsmentioning

confidence: 95%

mentioning

confidence: 92%

The Agrobacterium tumefaciens vir gene transcriptional activator virG is transcriptionally induced by acid pH and other stress stimuli

Mantis

Winans

1992

J Bacteriol

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“…2) has the highest homology with the E. coliconsensus [31]; therefore it seems likely that this is the preferred start codon in this organism. It is not known, however, whether Agrobacterium recognizes other signals as well; a recent report indicates that typical Shine-Delgarno sequences are lacking in some genes from the virulence (Vir) region of Ti plasmids [33]. For translation in Agrobacterium it may therefore be of significance that the potential start codon GUG is flanked by an inverted repeat, suggesting that RNA transcripts could form a stemloop structure with GUG in the loop (IR1 in Fig.…”

Section: Dna Sequence Of the Ocd Region And Deduced Amino Acid Sequenmentioning

confidence: 99%

Ornithine cyclodeaminase from Ti plasmid C58: DNA sequence, enzyme properties and regulation of activity by arginine

Sans

Schindler

Schröder

1988

European Journal of Biochemistry

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Nopaline, an abundant opine in plant cells transformed with nopaline-type Ti plasmids, is catabolized in Agrobacterium by three Ti-plasmid-coded steps via arginine and ornithine to proline. The last enzyme, ornithine cyclodeaminase (OCD), converts ornithine directly into proline with release of ammonia. We describe the DNA sequence of the ocd gene from Ti plasmid C58, antiserum against an OCD fusion protein overexpressed in Escherichia coli, induction and identification of the gene product in Agrobacterium and enzymatic properties of the protein. The DNA sequence suggests a soluble protein with a stretch of some homology with ornithine carbamoyltransferases from other bacteria. OCD activity is subject to substrate inhibition, is stimulated by NAD' @resumably acting as a catalytic cofactor) and is regulated by L-arginine which has pronounced effects on the optima for pH and temperature and on the K,,, for ornithine. The regulation of OCD activity by L-arginine is discussed as part of the mechanisms which integrate the pathway of Ti-plasmid-coded opine utilization with general metabolism in Agrobacterium.Ti-plasmid-mediated gene transfer from Agrobacteria to plants leads to marked changes in the properties of the transformed cells. They proliferate (forming neoplastic overgrowths called crown galls) and they synthesize and secrete novel substances (opines). Both properties are caused by specific transferred-DNA genes (reviewed in [l, 21). Opines can serve as a single source of carbon, nitrogen and energy in Ti-plasmid-containing Agrobacteria: it seems likely that this selective advantage played a role in the evolution of the interaction between these bacteria and plants (opine concept [3,41). An important part of this concept is that opine catabolism is a function of Ti plasmid genes. This basic prediction is supported by many studies, but in most cases neither the genes nor the enzymes have been characterized in any detail.Nopaline [Nz-(l ,3-dicarboxypropyl)-~-arginine] is a predominant opine in plant cells transformed with Ti plasmid pTiC58. We have shown recently [5] that the Noc region of this plasmid codes for at least three enzymes involved in catabolism of nopaline; together they constitute a pathway from nopaline via arginine and ornithine to proline (summarized in Fig. 1). The last enzyme, ornithine cyclodeaminase (OCD), converts ornithine with release of ammonia directly into proline; this type of enzyme reaction appears to be unusual even in bacteria. Apart from Agrobacterium [5 -71, it has been identified only in two Pseudomonas strains [9] and in some anaerobic bacteria [8 - has not yet been reported so we investigated the Ti-plasmidcoded gene and enzyme. Here we describe the DNA sequence, antiserum against a fusion protein over-expressed in Escherichia coli, the induction and identification of the protein in Agrobacterium, and properties of the enzyme. Interestingly, the activity is regulated by L-arginine, a precursor for the reaction catalyzed by OCD in the Ti-plasmid-coded pathway from nopaline to...

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“…Transcription of the virulence genes (vir) on the hairy-root-inducing plasmids (pRi) and tumor-inducing plasmids (pTi) is induced in Agrobacterium cells by plant signals through the VirA-VirG system, which is a two-component regulatory system [14]. VirA is anchored at the cell membrane [5,6] and appears to sense either directly or indirectly plant factors concurrent with autophosphorylation [7].…”

Section: Introductionmentioning

confidence: 99%

“…VirG cooperatively binds to vir promoter regions in which the 6-bp vir boxes are located in a helical phase [lO-121. RNA polymerase and VirG molecules could simultaneously interact with the vir promoter regions without steric hindrance because the helical phase of the vir boxes is nearly opposite to that of the -35 and -10 regions of the promoters [10,13]. However, the -35 and -10 region sequences, particularly the -35 region sequence, show a low degree of similarity to the respective consensus sequences of Escherichia coli promoters; nevertheless Agrobacterium constitutive promoters resemble E. coli promoters [3,14]. Therefore, RNA polymerase seems to be unable to interact with the vir promoters by itself, and the cooperative binding of VirG is likely to guide RNA polymerase to the promoters.…”

Section: Introductionmentioning

confidence: 99%

Transcription in vitro promoted by the Agrobacterium VirG protein

1993

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Expression of the virulence genes (vir) on the hairy-root-inducing plasmid pRiA4 is induced by plant signals in Agrobucterium cells through a two-component regulatory system, the VirA-VirG system. We constructed an in vitro transcription system that consisted of the purified VirG protein and the Agrobacterium RNA polymerase holoenzyme. Both versions of VirG, the non-phosphorylated form and the VirA-phosphorylated form, were active but showed different patterns of the pa-dependency for transcriptional activation.

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Promoters ofAgrobacterium tumefaciensTi-plasmid virulence genes

Cited by 88 publications

References 22 publications

The Agrobacterium tumefaciens vir gene transcriptional activator virG is transcriptionally induced by acid pH and other stress stimuli

The Agrobacterium tumefaciens vir gene transcriptional activator virG is transcriptionally induced by acid pH and other stress stimuli

Ornithine cyclodeaminase from Ti plasmid C58: DNA sequence, enzyme properties and regulation of activity by arginine

Transcription in vitro promoted by the Agrobacterium VirG protein

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