MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1
When grown under standard conditions, Sinorhizobium meliloti EFB1 simultaneously produces two acidic exopolysaccharides, succinoglycan and galactoglucan, yielding very mucoid colonies. In this strain, MucR is essential for galactoglucan synthesis. A mutation in the mucS gene resulted in less mucoid...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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The American Phytopathological Society
2002-01-01
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| Series: | Molecular Plant-Microbe Interactions |
| Online Access: | https://apsjournals.apsnet.org/doi/10.1094/MPMI.2002.15.1.54 |
| _version_ | 1811277725207363584 |
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| author | Javier Lloret Marta Martín Roke I. Oruezabal Ildefonso Bonilla Rafael Rivilla |
| author_facet | Javier Lloret Marta Martín Roke I. Oruezabal Ildefonso Bonilla Rafael Rivilla |
| author_sort | Javier Lloret |
| collection | DOAJ |
| description | When grown under standard conditions, Sinorhizobium meliloti EFB1 simultaneously produces two acidic exopolysaccharides, succinoglycan and galactoglucan, yielding very mucoid colonies. In this strain, MucR is essential for galactoglucan synthesis. A mutation in the mucS gene resulted in less mucoid colonies than in the wild-type EFB1. This mucS¯ strain was complemented to the wild-type phenotype by the cloned mucS gene, indicating that mucS is necessary for a wild-type level of galactoglucan production. Reverse transcription-polymerase chain reaction analysis of exp genes, which encode the pathway for galactoglucan production, in EFB1 and in the mutants affected in mucS, mucR, and both genes simultaneously, showed that MucS is a transcriptional activator of the exp genes but does not affect its own transcription. Furthermore, MucR is necessary for mucS transcriptional activation. As introduction of a cloned mucS gene in a mucR¯ strain yielded colonies less mucoid than the wild type, MucR could also activate exp genes transcription through other pathways. Deletion analysis of the expE promoter showed a region important for transcription and MucS activation. This region, containing a palindrome, is present in the putative expA, expC, expD, and expE promoters but not in the mucS promoter, suggesting that it is the target for MucS. A mucR¯mucS¯ mutant, which does not produce galactoglucan, was impaired in competitive nodulation of alfalfa in soil microcosms, indicating another possible role for this exopolysaccharide in symbiosis. |
| first_indexed | 2024-04-13T00:21:56Z |
| format | Article |
| id | doaj.art-148cf09ea029444fbc07c8078691d1d1 |
| institution | Directory Open Access Journal |
| issn | 0894-0282 1943-7706 |
| language | English |
| last_indexed | 2024-04-13T00:21:56Z |
| publishDate | 2002-01-01 |
| publisher | The American Phytopathological Society |
| record_format | Article |
| series | Molecular Plant-Microbe Interactions |
| spelling | doaj.art-148cf09ea029444fbc07c8078691d1d12022-12-22T03:10:44ZengThe American Phytopathological SocietyMolecular Plant-Microbe Interactions0894-02821943-77062002-01-01151545910.1094/MPMI.2002.15.1.54MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1Javier LloretMarta MartínRoke I. OruezabalIldefonso BonillaRafael RivillaWhen grown under standard conditions, Sinorhizobium meliloti EFB1 simultaneously produces two acidic exopolysaccharides, succinoglycan and galactoglucan, yielding very mucoid colonies. In this strain, MucR is essential for galactoglucan synthesis. A mutation in the mucS gene resulted in less mucoid colonies than in the wild-type EFB1. This mucS¯ strain was complemented to the wild-type phenotype by the cloned mucS gene, indicating that mucS is necessary for a wild-type level of galactoglucan production. Reverse transcription-polymerase chain reaction analysis of exp genes, which encode the pathway for galactoglucan production, in EFB1 and in the mutants affected in mucS, mucR, and both genes simultaneously, showed that MucS is a transcriptional activator of the exp genes but does not affect its own transcription. Furthermore, MucR is necessary for mucS transcriptional activation. As introduction of a cloned mucS gene in a mucR¯ strain yielded colonies less mucoid than the wild type, MucR could also activate exp genes transcription through other pathways. Deletion analysis of the expE promoter showed a region important for transcription and MucS activation. This region, containing a palindrome, is present in the putative expA, expC, expD, and expE promoters but not in the mucS promoter, suggesting that it is the target for MucS. A mucR¯mucS¯ mutant, which does not produce galactoglucan, was impaired in competitive nodulation of alfalfa in soil microcosms, indicating another possible role for this exopolysaccharide in symbiosis.https://apsjournals.apsnet.org/doi/10.1094/MPMI.2002.15.1.54 |
| spellingShingle | Javier Lloret Marta Martín Roke I. Oruezabal Ildefonso Bonilla Rafael Rivilla MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1 Molecular Plant-Microbe Interactions |
| title | MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1 |
| title_full | MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1 |
| title_fullStr | MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1 |
| title_full_unstemmed | MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1 |
| title_short | MucR and MucS Activate exp Genes Transcription and Galactoglucan Production in Sinorhizobium meliloti EFB1 |
| title_sort | mucr and mucs activate exp genes transcription and galactoglucan production in sinorhizobium meliloti efb1 |
| url | https://apsjournals.apsnet.org/doi/10.1094/MPMI.2002.15.1.54 |
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