Dataset Information

Expression of two members of the pMGA gene family of Mycoplasma gallisepticum oscillates and is influenced by pMGA-specific antibodies.

ABSTRACT: Certain monoclonal antibodies and polyclonal antisera directed to pMGA, the major protein of Mycoplasma gallisepticum, were tested for the ability to influence the surface phenotype of the cell population which resulted from their inclusion in growth medium. The polyclonal antiserum and one monoclonal antibody (MAb 66) resulted in an alteration of surface phenotype; specifically, populations of cells grown either on plates or in broth cultures which contained these reagents ceased the expression of pMGA and instead expressed an antigenically unrelated new polypeptide (p82). Upon the removal of antibody, the progeny of these cells regained pMGA expression and produced antigenically sectored colonies. The basis of this switch between pMGA+ and pMGA- states was shown to be transcriptional. The p82 polypeptide, the expression of which resulted from growth of cells in antibodies, was another member of the pMGA gene family and was located just downstream from the pMGA gene normally expressed by the M. gallisepticum cells used. Collectively the results of this work suggest that this organism has evolved an unusual means of altering the antigenic composition of its surface in response to antibodies or to other environmental cues.

SUBMITTER: Markham PF

PROVIDER: S-EPMC108280 | biostudies-literature | 1998 Jun

REPOSITORIES: biostudies-literature

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Expression of two members of the pMGA gene family of Mycoplasma gallisepticum oscillates and is influenced by pMGA-specific antibodies.

Markham P F PF Glew M D MD Browning G F GF Whithear K G KG Walker I D ID

Infection and immunity 19980601 6

Certain monoclonal antibodies and polyclonal antisera directed to pMGA, the major protein of Mycoplasma gallisepticum, were tested for the ability to influence the surface phenotype of the cell population which resulted from their inclusion in growth medium. The polyclonal antiserum and one monoclonal antibody (MAb 66) resulted in an alteration of surface phenotype; specifically, populations of cells grown either on plates or in broth cultures which contained these reagents ceased the expression ...[more]

PMID: 9596758

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Project description:Mycoplasma gallisepticum, the cause of chronic respiratory infections in the avian host, possesses a family of M9/pMGA genes encoding an adhesin(s) associated with hemagglutination. Nucleotide sequences of M9/pMGA gene family members indicate extensive sequence similarity in the promoter regions of both the transcribed and silent genes. The mechanism that regulates M9/pMGA gene expression is unknown, but studies have revealed an apparent correlation between gene expression and the number of tandem GAA repeat motifs located upstream of the putative promoter. In this study, transposon Tn4001 was used as a vector with the Escherichia coli lacZ gene as the reporter system to examine the role of the GAA repeats in M9/pMGA gene expression in M. gallisepticum. A 336-bp M9 gene fragment (containing the GAA repeat region, the promoter, and the translation start codon) was amplified by PCR, ligated with a lacZ gene from E. coli, and inserted into the Tn4001-containing plasmid pISM2062. This construct was transformed into M. gallisepticum PG31. Transformants were filter cloned on agar supplemented with 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) to monitor lacZ gene expression on the basis of blue/white color selection. Several cycles of filter cloning resulted in cell lineages in which lacZ gene expression alternated between the On and Off states in successive generations of progeny clones. The promoter regions of the M9-lacZ hybrid genes of individual progeny clones were amplified by PCR and sequenced. The only differences between the promoter regions of the blue and white colonies were in the number of GAA repeats. Clones that expressed lacZ had exactly 12 tandem copies of the GAA repeat. Clones that did not express lacZ invariably had either more than 12 (14 to 16) or fewer than 12 (5 to 11) GAA repeats. Southern analysis of M. gallisepticum chromosomal DNA confirmed that the phase-variable expression of the lacZ reporter gene was not caused by Tn4001 transposition. These data strongly indicate that changes in the length of the GAA repeat region are responsible for regulating M9/pMGA gene expression.

Dataset Information

Expression of two members of the pMGA gene family of Mycoplasma gallisepticum oscillates and is influenced by pMGA-specific antibodies.

Publications

Expression of two members of the pMGA gene family of Mycoplasma gallisepticum oscillates and is influenced by pMGA-specific antibodies.

Similar Datasets

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