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Differential regulation of interchromosomal copies of ToxR-induced genes

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In Vibrio cholerae, ToxR transcriptionally activates a number of virulence genes in response to various environmental signals. In the present study, transcription profiling by macroarray was carried out with 13 pairs of genes, one copy of which is present in each chromosome under ToxR-inducing (pH6.5, osmolarity 66mmol/L, 30°C) and ToxR-repressing (pH8.5, osmolarity 300mmol/L, 37°C) conditions followed by high pH (8.5) and low pH (6.5) conditions to eliminate pH effect. The genes dacAII, tagEII, secDII, pmmI, pmmII, and immII showed increased expression in the ToxR-inducing conditions, but not at low pH, suggesting that the expression of these genes might be regulated by ToxR. The expression of pmmII, dacAII, tagEII, secDII, and immII genes decreased significantly in the toxR insertion mutant as determined by RT–PCR, whereas the expression of the chromosomeI copy of pmm increased in toxR mutant compared with wild-type cells. Thus, the chromosomeII copy of these genes, which show increased expression under ToxR-inducing conditions, are all regulated by ToxR in V.cholerae, whereas the chromosomeI copy of pmm may be regulated by other factors under ToxR-inducing conditions.

ToxR active la transcription d’un certain nombre de gènes de virulence en réponse à différents signaux environnementaux chez Vibrio cholerae. Dans cette étude, nous avons réalisé un profil par micropuce de la transcription de treize paires de gènes, une copie de chacun étant présente sur chaque chromosome, sous des conditions d’induction (pH 6,5, osmolarité de 66 mmol/L, 30°C) ou de répression de Tox-R (pH 8,5, osmolarité 300 mmol/L, 37 °C), suivies de conditions de pH élevé (pH 8,5) ou faible (pH 6,5) afin d’éliminer les effets dus au pH. L’expression des gènes dacAII, tagEII, secDII, pmmI, pmmII et immII a augmenté sous des conditions d’induction de ToxR mais pas à faible pH, ce qui suggère que l’induction de ces gènes puisse être régulée par ToxR. L’expression des gènes pmmII, dacAII, tagEII, secDII et immII a diminué de façon significative chez des mutants d’insertion toxR tel que déterminé par RT–PCR, alors que l’expression de la copie de pmm du chromosome I a plutôt augmenté chez le mutant toxR comparativement aux cellules sauvages. Ainsi, les copies de ces gènes présentes sur le chromosome II, dont l’expression est augmentée sous des conditions d’induction de ToxR, sont toutes régulées par ToxR chez V.cholerae alors que la copie de pmm présente sur le chromosome I pourrait être régulée par d’autres facteurs sous les conditions d’induction de ToxR.

Document Type: Research Article

Publication date: 2007-08-01

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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