Genome-Wide Sensitivity Analysis of the Microsymbiont
The model legume species Medicago truncatula expresses more than 700 nodule-specific cysteine-rich (NCR) signaling peptides that mediate the differentiation of Sinorhizobium meliloti bacteria into nitrogen-fixing bacteroids. NCR peptides are essential for a successful symbiosis in legume plants of t...
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| Format: | Article |
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American Society for Microbiology
2018
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| Online Access: | http://hdl.handle.net/1721.1/114305 https://orcid.org/0000-0002-1515-3582 https://orcid.org/0000-0002-3104-5856 https://orcid.org/0000-0001-7243-8261 |
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| author | Boehme, Kevin L. Griffitts, Joel S. Shabab, Mohammed Penterman, Jon Arnold, Markus F. F. Walker, Graham C. |
| author2 | Massachusetts Institute of Technology. Department of Biology |
| author_facet | Massachusetts Institute of Technology. Department of Biology Boehme, Kevin L. Griffitts, Joel S. Shabab, Mohammed Penterman, Jon Arnold, Markus F. F. Walker, Graham C. |
| author_sort | Boehme, Kevin L. |
| collection | MIT |
| description | The model legume species Medicago truncatula expresses more than 700 nodule-specific cysteine-rich (NCR) signaling peptides that mediate the differentiation of Sinorhizobium meliloti bacteria into nitrogen-fixing bacteroids. NCR peptides are essential for a successful symbiosis in legume plants of the inverted-repeatlacking clade (IRLC) and show similarity to mammalian defensins. In addition to signaling functions, many NCR peptides exhibit antimicrobial activity in vitro and in vivo. Bacterial resistance to these antimicrobial activities is likely to be important for symbiosis. However, the mechanisms used by S. meliloti to resist antimicrobial activity of plant peptides are poorly understood. To address this, we applied a global genetic approach using transposon mutagenesis followed by high-throughput sequencing (Tn-seq) to identify S. meliloti genes and pathways that increase or decrease bacterial competitiveness during exposure to the well-studied cationic NCR247 peptide and also to the unrelated model antimicrobial peptide polymyxin B. We identified 78 genes and several diverse pathways whose interruption alters S. meliloti resistance to NCR 247. These genes encode the following: (i) cell envelope polysaccharide biosynthesis and modification proteins, (ii) inner and outer membrane proteins, (iii) peptidoglycan (PG) effector proteins, and (iv) non-membrane-associated factors such as transcriptional regulators and ribosomeassociated factors. We describe a previously uncharacterized yet highly conserved peptidase, which protects S. meliloti from NCR247 and increases competitiveness during symbiosis. Additionally, we highlight a considerable number of uncharacterized genes that provide the basis for future studies to investigate the molecular basis of symbiotic development as well as chronic pathogenic interactions. IMPORTANCE Soil rhizobial bacteria enter into an ecologically and economically important symbiotic interaction with legumes, in which they differentiate into physiologically distinct bacteroids that provide essential ammonia to the plant in return for carbon sources. Plant signal peptides are essential and specific to achieve these physiological changes. These peptides show similarity to mammalian defensin peptides which are part of the first line of defense to control invading bacterial populations. A number of these legume peptides are indeed known to possess antimicrobial activity, and so far, only the bacterial BacA protein is known to protect rhizobial bacteria against their antimicrobial action. This study identified numerous additional bacterial factors that mediate protection and belong to diverse biological pathways. Our results significantly contribute to our understanding of the molecular roles of bacterial factors during legume symbioses and, second, provide insights into the mechanisms that pathogenic bacteria may use to resist the antimicrobial effects of defensins during infections. KEYWORDS: antimicrobial peptides, host-microbe interactions, symbiosis |
| first_indexed | 2024-09-23T10:39:13Z |
| format | Article |
| id | mit-1721.1/114305 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T10:39:13Z |
| publishDate | 2018 |
| publisher | American Society for Microbiology |
| record_format | dspace |
| spelling | mit-1721.1/1143052022-09-30T22:03:39Z Genome-Wide Sensitivity Analysis of the Microsymbiont Boehme, Kevin L. Griffitts, Joel S. Shabab, Mohammed Penterman, Jon Arnold, Markus F. F. Walker, Graham C. Massachusetts Institute of Technology. Department of Biology Arnold, Markus Shabab, Mohammed Penterman, Jon Walker, Graham C The model legume species Medicago truncatula expresses more than 700 nodule-specific cysteine-rich (NCR) signaling peptides that mediate the differentiation of Sinorhizobium meliloti bacteria into nitrogen-fixing bacteroids. NCR peptides are essential for a successful symbiosis in legume plants of the inverted-repeatlacking clade (IRLC) and show similarity to mammalian defensins. In addition to signaling functions, many NCR peptides exhibit antimicrobial activity in vitro and in vivo. Bacterial resistance to these antimicrobial activities is likely to be important for symbiosis. However, the mechanisms used by S. meliloti to resist antimicrobial activity of plant peptides are poorly understood. To address this, we applied a global genetic approach using transposon mutagenesis followed by high-throughput sequencing (Tn-seq) to identify S. meliloti genes and pathways that increase or decrease bacterial competitiveness during exposure to the well-studied cationic NCR247 peptide and also to the unrelated model antimicrobial peptide polymyxin B. We identified 78 genes and several diverse pathways whose interruption alters S. meliloti resistance to NCR 247. These genes encode the following: (i) cell envelope polysaccharide biosynthesis and modification proteins, (ii) inner and outer membrane proteins, (iii) peptidoglycan (PG) effector proteins, and (iv) non-membrane-associated factors such as transcriptional regulators and ribosomeassociated factors. We describe a previously uncharacterized yet highly conserved peptidase, which protects S. meliloti from NCR247 and increases competitiveness during symbiosis. Additionally, we highlight a considerable number of uncharacterized genes that provide the basis for future studies to investigate the molecular basis of symbiotic development as well as chronic pathogenic interactions. IMPORTANCE Soil rhizobial bacteria enter into an ecologically and economically important symbiotic interaction with legumes, in which they differentiate into physiologically distinct bacteroids that provide essential ammonia to the plant in return for carbon sources. Plant signal peptides are essential and specific to achieve these physiological changes. These peptides show similarity to mammalian defensin peptides which are part of the first line of defense to control invading bacterial populations. A number of these legume peptides are indeed known to possess antimicrobial activity, and so far, only the bacterial BacA protein is known to protect rhizobial bacteria against their antimicrobial action. This study identified numerous additional bacterial factors that mediate protection and belong to diverse biological pathways. Our results significantly contribute to our understanding of the molecular roles of bacterial factors during legume symbioses and, second, provide insights into the mechanisms that pathogenic bacteria may use to resist the antimicrobial effects of defensins during infections. KEYWORDS: antimicrobial peptides, host-microbe interactions, symbiosis National Institutes of Health (Grant GM31030) 2018-03-27T14:04:08Z 2018-03-27T14:04:08Z 2017-08 2017-06 2018-02-23T19:15:06Z Article http://purl.org/eprint/type/JournalArticle 2150-7511 http://hdl.handle.net/1721.1/114305 Arnold, Markus F. F., et al. “Genome-Wide Sensitivity Analysis of the Microsymbiont Sinorhizobium Meliloti to Symbiotically Important, Defensin-Like Host Peptides.” MBio, edited by Frederick M. Ausubel, vol. 8, no. 4, Sept. 2017, pp. e01060-17. © 2017 Arnold et al. T https://orcid.org/0000-0002-1515-3582 https://orcid.org/0000-0002-3104-5856 https://orcid.org/0000-0001-7243-8261 http://dx.doi.org/10.1128/MBIO.01060-17 mBio Attribution 4.0 International (CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ application/pdf American Society for Microbiology |
| spellingShingle | Boehme, Kevin L. Griffitts, Joel S. Shabab, Mohammed Penterman, Jon Arnold, Markus F. F. Walker, Graham C. Genome-Wide Sensitivity Analysis of the Microsymbiont |
| title | Genome-Wide Sensitivity Analysis of the Microsymbiont |
| title_full | Genome-Wide Sensitivity Analysis of the Microsymbiont |
| title_fullStr | Genome-Wide Sensitivity Analysis of the Microsymbiont |
| title_full_unstemmed | Genome-Wide Sensitivity Analysis of the Microsymbiont |
| title_short | Genome-Wide Sensitivity Analysis of the Microsymbiont |
| title_sort | genome wide sensitivity analysis of the microsymbiont |
| url | http://hdl.handle.net/1721.1/114305 https://orcid.org/0000-0002-1515-3582 https://orcid.org/0000-0002-3104-5856 https://orcid.org/0000-0001-7243-8261 |
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