Octopine‐type Ti plasmids code for a mannopine‐inducible dominant‐negative allele of <i>traR</i>, the quorum‐sensing activator that regulates Ti plasmid conjugal transfer

Oger, Philippe; Kim, Kun-Soo; Sackett, Rebecca L.; Piper, Kevin R.; Farrand, Stephen K.

doi:10.1046/j.1365-2958.1998.00671.x

Cited by 88 publications

(113 citation statements)

References 37 publications

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“…Clearly, the availability of opines constitutes the primary determinant for initiating the induction of the conjugal transfer process. Opines trigger conjugation by controlling the expression of traR (15,30,35). Furthermore, the active traR alleles of all Ti plasmids examined to date are expressed as components of opine-regulated operons, suggesting that regulation by these nutrient sources is important to the biology of Ti plasmid transfer (15,30,35; reviewed in reference 12).…”

Section: Discussionmentioning

confidence: 99%

Quorum Sensing but Not Autoinduction of Ti Plasmid Conjugal Transfer Requires Control by the Opine Regulon and the Antiactivator TraM

Piper¹,

Farrand

2000

J Bacteriol

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Conjugal transfer of the Ti plasmids from Agrobacterium tumefaciens is controlled by autoinduction via the transcriptional activator TraR and the acyl-homoserine lactone ligand, Agrobacterium autoinducer (AAI). This control process is itself regulated by opines, which are small carbon compounds produced by the crown gall tumors that are induced by the bacteria. Opines control autoinduction by regulating the expression of traR. Transfer of pTiC58 from donors grown with agrocinopines A and B, the conjugal opines for this Ti plasmid, was detected only after the donors had reached a population level of 10 7 cells per cm 2 . Donors incubated with the opines and AAI transferred their Ti plasmids at population levels about 10-fold lower than those incubated with opines only. Transcription of the tra regulon, as assessed by monitoring a traA::lacZ reporter, showed a similar dependence on the density of the donor population. However, even in cultures at low population densities that were induced with opines and AAI, there was a temporal lag of between 15 and 20 h in the development of conjugal competence. Moreover, even after this latent period, maximal transfer frequencies required several hours to develop. This lag period was independent of the population density of the donors but could be reduced somewhat by addition of exogenous AAI. Quorum-dependent development of conjugal competence required control by the opine regulon; donors harboring a mutant of pTiC58 deleted for the master opine responsive repressor accR transferred the Ti plasmid at maximum frequencies at very low population densities. Similarly, an otherwise wild-type derivative of pTiC58 lacking traM, which codes for an antiactivator that inhibits TraR activity, transferred at high frequency in a population-independent manner in the absence of the conjugal opines. Thus, while quorum sensing is dependent upon autoinduction, the two phenomena are not synonymous. We conclude that conjugal transfer of pTiC58 is regulated in a quorum-dependent fashion but that supercontrol of the TraR-AAI system by opines and by TraM results in a complex control process that requires not only the accumulation of AAI but also the expression of TraR and the synthesis of this protein at levels that overcome the inhibitory activity of TraM.Conjugal transfer of the Ti plasmids from Agrobacterium tumefaciens is regulated directly by the transcriptional activator TraR and its acyl-homoserine lactone (acyl-HSL) ligand, Agrobacterium autoinducer [AAI; N-(3-oxo-octanoyl)-L-homoserine lactone] (16, 34, 40; reviewed in reference 12). TraR, in its interaction with AAI, controls conjugation by autoinduction, a process by which the bacteria induce gene sets in response to signals they themselves produce. This regulatory strategy is believed to tie plasmid transfer to the population density of the donor in what has come to be called the quorumsensing effect (reviewed in reference 18). The acyl-HSL autoinducers, which are produced by the bacteria themselves, are released into the environment, w...

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Section: Discussionmentioning

confidence: 99%

Quorum Sensing but Not Autoinduction of Ti Plasmid Conjugal Transfer Requires Control by the Opine Regulon and the Antiactivator TraM

Piper¹,

Farrand

2000

J Bacteriol

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“…Interestingly, TrlR expression is greatly enhanced in the presence of mannopine, a type of opine synthesized by the host plant. Mannopine is known to strongly inhibit conjugation in A. tumefaciens (100).…”

Section: Homologs Of Transcriptional Regulatorsmentioning

confidence: 99%

Messing with Bacterial Quorum Sensing

Gonzalez

Keshavan

2006

Microbiol Mol Biol Rev

376

232

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SUMMARY Quorum sensing is widely recognized as an efficient mechanism to regulate expression of specific genes responsible for communal behavior in bacteria. Several bacterial phenotypes essential for the successful establishment of symbiotic, pathogenic, or commensal relationships with eukaryotic hosts, including motility, exopolysaccharide production, biofilm formation, and toxin production, are often regulated by quorum sensing. Interestingly, eukaryotes produce quorum-sensing-interfering (QSI) compounds that have a positive or negative influence on the bacterial signaling network. This eukaryotic interference could result in further fine-tuning of bacterial quorum sensing. Furthermore, recent work involving the synthesis of structural homologs to the various quorum-sensing signal molecules has resulted in the development of additional QSI compounds that could be used to control pathogenic bacteria. The creation of transgenic plants that express bacterial quorum-sensing genes is yet another strategy to interfere with bacterial behavior. Further investigation on the manipulation of quorum-sensing systems could provide us with powerful tools against harmful bacteria.

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“…The homologues listed are present on the Ti plasmids specifically. ‡ The trlR gene contains a frameshift mutation in the 3h end of the normal reading frame (Oger et al, 1998 ;Zhu & Winans, 1998). This point mutation was corrected to generate a gene product that more accurately reflects its relationship to other members of the LuxR family.…”

Section: Introductionmentioning

confidence: 99%

The evolution of bacterial LuxI and LuxR quorum sensing regulators

2001

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Quorum sensing is a widespread form of bacterial communication in which individual cells produce and respond to specific N-acyl homoserine lactone signal metabolites. The different autoinducer synthases that generate these signals and the receptor/activator proteins that mediate the cell's response to them constitute evolutionarily conserved families of regulatory proteins known as the LuxI and LuxR families, respectively. We have performed a phylogenetic analysis of 76 individual LuxI and LuxR homologues present in diverse members of the Gram-negative Proteobacteria. The results were consistent with an early origin for these regulators during the evolution of the Proteobacteria, with functional pairs of luxI and luxR genes possibly coevolving as regulatory cassettes. In many cases, specific LuxI and LuxR family members appeared to have been inherited horizontally. In particular, those species containing multiple LuxI and/or LuxR homologues usually appeared to have obtained each individual homologue or functional pair of homologues from an independent source. Because multiple homologues interact to form regulatory cascades, this finding suggests that hierarchical signalling pathways can potentially evolve by the sequential integration of pre-existing regulatory circuits acquired from diverse sources.

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Octopine‐type Ti plasmids code for a mannopine‐inducible dominant‐negative allele of traR, the quorum‐sensing activator that regulates Ti plasmid conjugal transfer

Cited by 88 publications

References 37 publications

Quorum Sensing but Not Autoinduction of Ti Plasmid Conjugal Transfer Requires Control by the Opine Regulon and the Antiactivator TraM

Quorum Sensing but Not Autoinduction of Ti Plasmid Conjugal Transfer Requires Control by the Opine Regulon and the Antiactivator TraM

Messing with Bacterial Quorum Sensing

The evolution of bacterial LuxI and LuxR quorum sensing regulators

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