Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum
Symbiosis between Rhizobium leguminosarum and Pisum sativum requires tight control of redox balance in order to maintain respiration under the microaerobic conditions required for nitrogenase, whilst still producing the eight electrons and sixteen molecules of ATP needed for nitrogen fixation. FixAB...
| Main Authors: | , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
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American Phytopathological Society
2021
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| _version_ | 1797054151947976704 |
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| author | Webb, I Xu, J Sánchez-Cañizares, C Karunakaran, R Ramachandran, V Rutten, P East, A Huang, W Watmough, NJ Poole, P |
| author_facet | Webb, I Xu, J Sánchez-Cañizares, C Karunakaran, R Ramachandran, V Rutten, P East, A Huang, W Watmough, NJ Poole, P |
| author_sort | Webb, I |
| collection | OXFORD |
| description | Symbiosis between Rhizobium leguminosarum and Pisum sativum requires tight control of redox balance in order to maintain respiration under the microaerobic conditions required for nitrogenase, whilst still producing the eight electrons and sixteen molecules of ATP needed for nitrogen fixation. FixABCX, electron transfer flavoproteins essential for nitrogen fixation, are encoded on the Sym plasmid (pRL10), immediately upstream of nifA, which encodes the general transcriptional regulator of nitrogen fixation. There is a symbiotically-regulated NifA-dependent promoter upstream of fixA (PnifA1), as well as an additional basal constitutive promoter driving background expression of nifA (PnifA2). These were confirmed by 5’-end mapping of transcription start sites using differential (d) RNA-seq. Complementation of polar fixAB and fixX mutants (Fix- strains) confirmed expression of nifA from PnifA1 in symbiosis. Electron microscopy combined with single-cell Raman microspectroscopy characterization of fixAB mutants revealed previously unknown heterogeneity in bacteroid morphology within a single nodule. Two morphotypes of mutant fixAB bacteroids were observed. One was larger than wild-type bacteroids and contained high levels of polyhydroxy-3-butyrate, a complex energy/reductant storage product. A second bacteroid phenotype was morphologically and compositionally different and resembled wild-type infection thread cells. From these two characteristic fixAB mutant bacteroid morphotypes, inferences can be drawn on the metabolism of wild-type nitrogen-fixing bacteroids. |
| first_indexed | 2024-03-06T18:53:10Z |
| format | Journal article |
| id | oxford-uuid:10ef8fbc-f34f-4c35-bc9a-79cfa1695629 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T18:53:10Z |
| publishDate | 2021 |
| publisher | American Phytopathological Society |
| record_format | dspace |
| spelling | oxford-uuid:10ef8fbc-f34f-4c35-bc9a-79cfa16956292022-03-26T09:59:23ZRegulation and characterization of mutants of fixABCX in Rhizobium leguminosarumJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:10ef8fbc-f34f-4c35-bc9a-79cfa1695629EnglishSymplectic ElementsAmerican Phytopathological Society2021Webb, IXu, JSánchez-Cañizares, CKarunakaran, RRamachandran, VRutten, PEast, AHuang, WWatmough, NJPoole, PSymbiosis between Rhizobium leguminosarum and Pisum sativum requires tight control of redox balance in order to maintain respiration under the microaerobic conditions required for nitrogenase, whilst still producing the eight electrons and sixteen molecules of ATP needed for nitrogen fixation. FixABCX, electron transfer flavoproteins essential for nitrogen fixation, are encoded on the Sym plasmid (pRL10), immediately upstream of nifA, which encodes the general transcriptional regulator of nitrogen fixation. There is a symbiotically-regulated NifA-dependent promoter upstream of fixA (PnifA1), as well as an additional basal constitutive promoter driving background expression of nifA (PnifA2). These were confirmed by 5’-end mapping of transcription start sites using differential (d) RNA-seq. Complementation of polar fixAB and fixX mutants (Fix- strains) confirmed expression of nifA from PnifA1 in symbiosis. Electron microscopy combined with single-cell Raman microspectroscopy characterization of fixAB mutants revealed previously unknown heterogeneity in bacteroid morphology within a single nodule. Two morphotypes of mutant fixAB bacteroids were observed. One was larger than wild-type bacteroids and contained high levels of polyhydroxy-3-butyrate, a complex energy/reductant storage product. A second bacteroid phenotype was morphologically and compositionally different and resembled wild-type infection thread cells. From these two characteristic fixAB mutant bacteroid morphotypes, inferences can be drawn on the metabolism of wild-type nitrogen-fixing bacteroids. |
| spellingShingle | Webb, I Xu, J Sánchez-Cañizares, C Karunakaran, R Ramachandran, V Rutten, P East, A Huang, W Watmough, NJ Poole, P Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum |
| title | Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum |
| title_full | Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum |
| title_fullStr | Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum |
| title_full_unstemmed | Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum |
| title_short | Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum |
| title_sort | regulation and characterization of mutants of fixabcx in rhizobium leguminosarum |
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