A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator
ICEMlSymR7A of Mesorhizobium loti is an integrative and conjugative element (ICE) that confers the ability to form a nitrogen-fixing symbiosis with Lotus species. Horizontal transfer is activated by TraR and N-acyl-homoserine lactone (AHL), which can stimulate ICE excision in 100% of cells. However,...
| Main Authors: | , , , , , , , |
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| Format: | Journal Article |
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BLACKWELL PUBLISHING
2013
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| Online Access: | http://hdl.handle.net/20.500.11937/32760 |
| _version_ | 1848753752777949184 |
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| author | Ramsay, Joshua Major, A. Komarovsky, V. Sullivan, J. Dy, R. Hynes, M. Salmond, G. Ronson, C. |
| author_facet | Ramsay, Joshua Major, A. Komarovsky, V. Sullivan, J. Dy, R. Hynes, M. Salmond, G. Ronson, C. |
| author_sort | Ramsay, Joshua |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | ICEMlSymR7A of Mesorhizobium loti is an integrative and conjugative element (ICE) that confers the ability to form a nitrogen-fixing symbiosis with Lotus species. Horizontal transfer is activated by TraR and N-acyl-homoserine lactone (AHL), which can stimulate ICE excision in 100% of cells. However, in wild-type cultures, the ICE is excised at low frequency. Here we show that QseM, a widely conserved ICE-encoded protein, is an antiactivator of TraR. Mutation of qseM resulted in TraR-dependent activation of AHL production and excision, but did not affect transcription of traR. QseM and TraR directly interacted in a bacterial two-hybrid assay in the presence of AHL. qseM expression was repressed by a DNA-binding protein QseC, which also activated qseC expression from a leaderless transcript. QseC differentially bound two adjacent operator sites, the lower affinity of which overlapped the -35 regions of the divergent qseCqseM promoters. QseC homologues were identified on ICEs, TraR/TraM-regulated plasmids and restriction-modification cassettes, suggesting a conserved mode of regulation. Six QseC variants with distinct operators were identified that showed evidence of reassortment between mobile elements. We propose that QseC and QseM comprise a bimodal switch that restricts quorum sensing and ICEMlSymR7A transfer to a small proportion of cells in the population. |
| first_indexed | 2025-11-14T08:29:31Z |
| format | Journal Article |
| id | curtin-20.500.11937-32760 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:29:31Z |
| publishDate | 2013 |
| publisher | BLACKWELL PUBLISHING |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-327602017-09-13T15:27:37Z A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator Ramsay, Joshua Major, A. Komarovsky, V. Sullivan, J. Dy, R. Hynes, M. Salmond, G. Ronson, C. ICEMlSymR7A of Mesorhizobium loti is an integrative and conjugative element (ICE) that confers the ability to form a nitrogen-fixing symbiosis with Lotus species. Horizontal transfer is activated by TraR and N-acyl-homoserine lactone (AHL), which can stimulate ICE excision in 100% of cells. However, in wild-type cultures, the ICE is excised at low frequency. Here we show that QseM, a widely conserved ICE-encoded protein, is an antiactivator of TraR. Mutation of qseM resulted in TraR-dependent activation of AHL production and excision, but did not affect transcription of traR. QseM and TraR directly interacted in a bacterial two-hybrid assay in the presence of AHL. qseM expression was repressed by a DNA-binding protein QseC, which also activated qseC expression from a leaderless transcript. QseC differentially bound two adjacent operator sites, the lower affinity of which overlapped the -35 regions of the divergent qseCqseM promoters. QseC homologues were identified on ICEs, TraR/TraM-regulated plasmids and restriction-modification cassettes, suggesting a conserved mode of regulation. Six QseC variants with distinct operators were identified that showed evidence of reassortment between mobile elements. We propose that QseC and QseM comprise a bimodal switch that restricts quorum sensing and ICEMlSymR7A transfer to a small proportion of cells in the population. 2013 Journal Article http://hdl.handle.net/20.500.11937/32760 10.1111/mmi.12079 BLACKWELL PUBLISHING restricted |
| spellingShingle | Ramsay, Joshua Major, A. Komarovsky, V. Sullivan, J. Dy, R. Hynes, M. Salmond, G. Ronson, C. A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator |
| title | A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator |
| title_full | A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator |
| title_fullStr | A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator |
| title_full_unstemmed | A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator |
| title_short | A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator |
| title_sort | widely conserved molecular switch controls quorum sensing and symbiosis island transfer in mesorhizobium loti through expression of a novel antiactivator |
| url | http://hdl.handle.net/20.500.11937/32760 |