ORCID Profile
0000-0002-2945-0369
Current Organisations
Université Claude Bernard Lyon 1
,
INRAE
,
Centre National de la Recherche Scientifique
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Publications
Analysis of Quorum-Sensing-Dependent Control of Rhizosphere-Expressed ( rhi ) Genes in Rhizobium leguminosarum bv. viciae
Publisher: American Society for Microbiology
Date: 15-06-1999
DOI: 10.1128/JB.181.12.3816-3823.1999
Abstract: The rhi genes of Rhizobium leguminosarum biovar viciae are expressed in the rhizosphere and play a role in the interaction with legumes, such as the pea. Previously (K. M. Gray, J. P. Pearson, J. A. Downie, B. E. A. Boboye, and E. P. Greenberg, J. Bacteriol. 178:372–376, 1996) the rhiABC operon had been shown to be regulated by RhiR and to be induced by added N -(3-hydroxy-7- cis -tetradecenoyl)- l -homoserine lactone (3OH,C 14:1 -HSL). Mutagenesis of a cosmid carrying the rhiABC and rhiR gene region identified a gene ( rhiI ) that affects the level of rhiA expression. Mutation of rhiI slightly increased the number of nodules formed on the pea. The rhiI gene is (like rhiA ) regulated by rhiR in a cell density-dependent manner. RhiI is similar to LuxI and other proteins involved in the synthesis of N -acyl-homoserine lactones (AHLs). Chemical analyses of spent culture supernatants demonstrated that RhiI produces N -(hexanoyl)- l -homoserine lactone (C 6 -HSL) and N -(octanoyl)- l -homoserine lactone (C 8 -HSL). Both of these AHLs induced rhiA-lacZ and rhiI-lacZ expression on plasmids introduced into an Agrobacterium strain that produces no AHLs, showing that rhiI is positively regulated by autoinduction. However, in this system no induction of rhiA or rhiI with 3OH,C 14:1 -HSL was observed. Analysis of the spent culture supernatant of the wild-type R. leguminosarum bv. viciae revealed that at least seven different AHLs are made. Mutation of rhiI decreased the amounts of C 6 -HSL and C 8 -HSL but did not block their formation, and in this background the rhiI mutation did not significantly affect the expression levels of the rhiI gene or rhiABC genes or the accumulation of RhiA protein. These observations suggest that there are additional loci involved in AHL production in R. leguminosarum bv. viciae and that they affect rhiI and rhiABC expression. We postulate that the previously observed induction of rhiA by 3OH,C 14:1 -HSL may be due to an indirect effect caused by induction of other AHL production loci.
Electrospinning of polymer nanofibers: Effects on oriented morphology, structures and tensile properties
Publisher: Elsevier BV
Date: 05-2010
raiIR Genes Are Part of a Quorum-Sensing Network Controlled by cinI and cinR in Rhizobium leguminosarum<
Publisher: American Society for Microbiology
Date: 15-03-2002
DOI: 10.1128/JB.184.6.1597-1606.2002
Abstract: Analysis of N -acyl- l -homoserine lactones (AHLs) produced by Rhizobium leguminosarum bv. viciae indicated that there may be a network of quorum-sensing regulatory systems producing multiple AHLs in this species. Using a strain lacking a symbiosis plasmid, which carries some of the quorum-sensing genes, we isolated mutations in two genes ( raiI and raiR ) that are required for production of AHLs. The raiIR genes are located adjacent to dad genes (involved in d -alanine catabolism) on a large indigenous plasmid. RaiR is predicted to be a typical LuxR-type quorum-sensing regulator and is required for raiI expression. The raiR gene was expressed at a low level, possibly from a constitutive promoter, and its expression was increased under the influence of the upstream raiI promoter. Using gene fusions and analysis of AHLs produced, we showed that expression of raiI is strongly reduced in strains carrying mutations in cinI or cinR , genes which determine a higher-level quorum-sensing system that is required for normal expression of raiIR . The product of CinI, N -(3-hydroxy-7- cis tetradecenoyl) homoserine lactone, can induce raiR -dependent raiI expression, although higher levels of expression are induced by other AHLs. Expression of raiI in a strain of Agrobacterium that makes no AHLs resulted in the identification of N -(3-hydroxyoctanoyl)- l -homoserine lactone (3OH,C 8 -HSL) as the major product of RaiI, although other AHLs that comigrate with N -hexanoyl-, N -heptanoyl-, and N -octanoyl-homoserine lactones were also made at low levels. The raiI gene was strongly induced by 3OH,C 8 -HSL (the product of RaiI) but could also be induced by other AHLs, suggesting that the raiI promoter can be activated by other quorum-sensing systems within a network of regulation which also involves AHLs determined by genes on the symbiotic plasmid. Thus, the raiIR and cinIR genes are part of a complex regulatory network that influences AHL biosynthesis in R. leguminosarum .
The cin and rai Quorum-Sensing Regulatory Systems in Rhizobium leguminosarum Are Coordinated by ExpR and Ci
Publisher: American Society for Microbiology
Date: 05-2009
DOI: 10.1128/JB.01650-08
Abstract: To understand how the Rhizobium leguminosarum raiI-raiR quorum-sensing system is regulated, we identified mutants with decreased levels of RaiI-made N -acyl homoserine lactones (AHLs). A LuxR-type regulator, ExpR, is required for raiR expression, and RaiR is required to induce raiI . Since raiR (and raiI ) expression is also reduced in cinI and cinR quorum-sensing mutants, we thought CinI-made AHLs may activate ExpR to induce raiR . However, added CinI-made AHLs did not induce raiR expression in a cinI mutant. The reduced raiR expression in cinI and cinR mutants was due to lack of expression of cinS immediately downstream of cinI. cinS encodes a 67-residue protein, translationally coupled to CinI, and cinS acts downstream of expR for raiR induction. Cloned cinS in R. leguminosarum caused an unusual collapse of colony structure, and this was delayed by mutation of expR . The phenotype looked like a loss of exopolysaccharide (EPS) integrity mutations in cinI, cinR, cinS , and expR all reduced expression of plyB , encoding an EPS glycanase, and mutation of plyB abolished the effect of cloned cinS on colony morphology. We conclude that CinS and ExpR act to increase PlyB levels, thereby influencing the bacterial surface. CinS is conserved in other rhizobia, including Rhizobium etli the previously observed effect of cinI and cinR mutations decreasing swarming in that strain is primarily due to a lack of CinS rather than a lack of CinI-made AHL. We conclude that CinS mediates quorum-sensing regulation because it is coregulated with an AHL synthase and demonstrate that its regulatory effects can occur in the absence of AHLs.
Quorum-sensing in Rhizobium
Publisher: Springer Science and Business Media LLC
Date: 2002
Abstract: Quorum-sensing signals are found in many species of legume-nodulating rhizobia. In a well-characterized strain of R. leguminosarum biovar viciae, a variety of autoinducers are synthesised, and all have been identified as N-acyl-homoserine lactones. One of these N-acyl-homoserine lactones, is N-(3-hydroxy-7-cis-tetradecenoyl)-L-homoserine lactone, previously known as small bacteriocin, which inhibits the growth of several R. leguminosarum strains. The cinRI locus is responsible for the production of small bacteriocin. CinR induces cinl in response to the AHL made by Cinl, thus forming a positive autoregulatory induction loop. A complex cascade of quorum-sensing loops was characterized, in which the cinMR locus appears to be the master control for three other AHL-dependent quorum-sensing control systems. These systems include the rail/raiR, trallyriR and rhiI/rhiR. Other rhizobial strains appear to share some of these quorum sensing loci, but not all loci are found in all strains. Small bacteriocin along with the other N-acyl-homoserine lactones produced by these three AHL-based control systems regulate (i) growth inhibition of sensitive strains, (ii) transfer of the symbiotic plasmid pRL1JI, and (iii) expression of the rhizosphere-expressed (rhi) genes that influence nodulation. Some of the genes regulated by these systems have been identified. While the functions of some, such as the trb operon regulated by triR are clear, several of the regulated genes have no homologues of known function. It is anticipated that several other genes regulated by these systems have yet to be identified. Therefore, despite the regulation of one of the most complex quorum-sensing cascade being understood, several of the functions regulated by the quorum-sensing genes remain to be elucidated.
N -Acyl-Homoserine Lactone Inhibition of Rhizobial Growth Is Mediated by Two Quorum-Sensing Genes That Regulate Plasmid Transfer
Publisher: American Society for Microbiology
Date: 15-08-2002
DOI: 10.1128/JB.184.16.4510-4519.2002
Abstract: The growth of some strains of Rhizobium leguminosarum bv. viciae is inhibited by N -(3-hydroxy-7- cis tetradecenoyl)- l -homoserine lactone (3OH-C 14:1 -HSL), which was previously known as the small bacteriocin before its characterization as an N -acyl homoserine lactone (AHL). Tn 5 -induced mutants of R. leguminosarum bv. viciae resistant to 3OH-C 14:1 -HSL were isolated, and mutations in two genes were identified. These genes, bisR and triR , which both encode LuxR-type regulators required for plasmid transfer, were found downstream of an operon containing trb genes involved in the transfer of the symbiotic plasmid pRL1JI. The first gene in this operon is traI , which encodes an AHL synthase, and the trbBCDEJKLFGHI genes were found between traI and bisR . Mutations in bisR , triR , traI , or trbL blocked plasmid transfer. Using gene fusions, it was demonstrated that bisR regulates triR in response to the presence of 3OH-C 14:1 -HSL. In turn, triR is then required for the induction of the traI-trb operon required for plasmid transfer. bisR also represses expression of cinI , which is chromosomally located and determines the level of production of 3OH-C 14:1 -HSL. The cloned bisR and triR genes conferred 3OH-C 14:1 -HSL sensitivity to strains of R. leguminosarum bv. viciae normally resistant to this AHL. Furthermore, bisR and triR made Agrobacterium tumefaciens sensitive to R. leguminosarum bv. viciae strains producing 3OH-C 14:1 -HSL. Analysis of patterns of growth inhibition using mutant strains and synthetic AHLs revealed that maximal growth inhibition required, in addition to 3OH-C 14:1 -HSL, the presence of other AHLs such as N -octanoyl -l- homoserine lactone and/or N -(3-oxo-octanoyl) -l- homoserine lactone. In an attempt to identify the causes of growth inhibition, a strain of R. leguminosarum bv. viciae carrying cloned bisR and triR was treated with an AHL extract containing 3OH-C 14:1 -HSL. N-terminal sequencing of induced proteins revealed one with significant similarity to the protein translation factor Ef-Ts.
The regulatory locus cinRI in Rhizobium leguminosarum controls a network of quorum-sensing loci
Publisher: Wiley
Date: 07-2000
DOI: 10.1046/J.1365-2958.2000.01960.X
Abstract: N-(3-hydroxy-7-cis-tetradecenoyl)-L-homoserine lactone (3OH, C14:1-HSL) is a quorum-sensing signalling molecule produced by Rhizobium leguminosarum. It is unusual in that it inhibits the growth of several strains of R. leguminosarum and was previously known as 'small bacteriocin'. The cinRI locus responsible for the production of 3OH,C14:1-HSL has been characterized it is predicted to be on the chromosome, based on DNA hybridization. The cinR and cinI genes are in different transcriptional units, separated by a predicted transcription terminator. CinR regulates cinI expression to a very high level in a cell-density dependent manner, and cinI expression is positively autoregulated by 3OH,C14:1-HSL, the only identified N-acyl homoserine lactone (AHL) produced by CinI. No other AHLs were identified that strongly induced cinI expression. Mutation of cinI or cinR abolishes the production of 3OH,C14:1-HSL and also reduces the production of several other AHLs. This is thought to result from the expression of three other AHL production loci being affected by the absence of 3OH,C14:1-HSL. AHLs produced by these other loci include N-hexanoyl- and N-octanoyl-L-homoserine lactones and, unexpectedly, N-heptanoyl-L-homoserine lactone (C7-HSL). The expression of the rhiI gene on the symbiotic plasmid is greatly reduced in a cinI mutant, and the major regulatory effect appears to be mediated at least in part as a result of an effect on expression of RhiR, the regulator of rhiI. Thus, cinR and cinI appear to be at the top of a regulatory cascade or network that influences several AHL-regulated quorum-sensing loci. The expression of cinI-lacZ fusions is significantly reduced (but not abolished) when the symbiosis plasmid pRL1JI is present, resulting in a reduction in the level of 3OH,C14:1-HSL produced. Mutation of cinI had little effect on growth or nodulation. However, plasmid transfer was affected, and the results obtained indicate that 3OH,C14:1-HSL produced by either the donor or the recipient in mating experiments can stimulate transfer of pRL1JI.
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No related grants have been discovered for Florence Wisniewski-Dyé.