Infection of legume roots with Rhizobium species results in the development of a root nodule structure in which the bacteria form an intracellular symbiosis with the plant. It is reported here that the infection of soybean (Glycine max L.) roots with Rhizobium japonicum results in the synthesis by the plant of at least 18-20 polypeptides other than leghemoglobin during the development of root nodules. Identification of these "nodule-specific" host polypeptides (referred to as nodulins) was accomplished by two-dimensional gel analysis of the immunoprecipitates formed by a "nodule-specific" antiserum with in vitro translation products of root nodule polysomes that are free of bacteroidal contaminations. Nodulins account for 7-11% of the total ('35)S-methionine-labeled protein synthesized in the host cell cytoplasm, and the majority of them are of 12,000-20,000 molecular weight. These proteins are absent from the uninfected roots, bacteroids and free-living Rhizobium, and appear to be coded for by the plant genes that may be obligatory for the development of symbiosis in the legume root nodules. Analysis of nodulins in ineffective (unable to fix nitrogen) nodules developed due to Rhizobium strains SM5 and 61A24 showed that their synthesis is reduced and their expression differentially influenced by mutations in rhizobia. / Apart from the low molecular weight nodulins, a 35,000 MW polypeptide present in the nodule cytoplasm was also identified as "nodule-specific". This protein, referred to as nodulin-35, represents about 4% of the total cytoplasmic protein in root nodules, and its appearance is not affected by mutations in several nodulating strains of Rhizobium. Nodulin-35 was not detected in uninfected soybean, bacteroids or free-living Rhizobium, and it appears to be synthesized by the plant during the formation of root nodules. / Whereas the transformation of free-living Rhizobium into bacteroids is accompanied by substantial changes within the population of cytoplasmic proteins, the majority of plant polypeptides from nodules are also present in uninfected (non-nodulated) roots. Hence, to further identify and isolate the "nodule-specific" proteins, it was essential to develop several immunological procedures, including a preparative adsorption of antibodies with antigens, the multiple immunoreplica technique, and isolation of a single-copy mRNA by immunoprecipitation of the nascent peptide-polysome complex, which are described in this thesis. / In addition, two polypeptides of bacterial origin were found to be cross-reactive with the "nodule-specific" antiserum, suggesting that they are secreted into the host cell cytoplasm during symbiotic nitrogen fixation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.68628 |
| Date | January 1982 |
| Creators | Legocki, Roman Przemyslaw. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000139594, proquestno: AAINK58133, Theses scanned by UMI/ProQuest. |
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