Thesis (Ph. D.)--University of Wisconsin--Madison, 1948. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [30-32]).

In order to identify plant genes involved in the Rhizobium/legume root nodule symbiosis, host gene expression during soybean nodule development was studied. The hybridization of complementary DNA (cDNA) probes with homologous and heterologous polyadenylated polysomal RNAs showed that most of the 20,000-25,000 RNA sequences expressed were common to uninfected root and nodule tissues. There was a marked increase in the relative concentration of leghaemoglobin and moderately abundant nodule sequences following infection by Rhizobium. A nodule-specific cDNA probe (NS-cDNA), prepared by eliminating common root sequences by cascade hydroxylapatite chromatography, was used to characterize a small population of nodule-specific sequences. Hybridization of NS-cDNA to DNA from soybean embryos and not to Rhizobium demonstrated that these sequences are encoded by the host genome. Hybridization with nuclear RNA from uninfected tissues showed that the primary mode of regulation of these sequences is at the level of transcription. Expression of these small nodule-specific-mRNAs is differentially modulated by ineffective strains of Rhizobium. The relative concentration of nodule-specific and common moderately abundant sequences increased to varying extents, in parallel with leghaemoglobin, reaching a peak when nitrogen fixation commences. These data suggest that host gene expression is coordinately regulated during early nodule development. Indoleacetic acid appeared to modulate the expression of common moderately abundance sequences, but had no detectable effect upon leghaemoglobin or nodule-specific sequences. Preliminary characterization of 26 cDNA clones indicated that, in addition to leghaemoglobin and other positively regulated sequences, there were two clones whose mRNA concentration decreased during nodule development.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1954. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [56]-60).

No description available.

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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.

No description available.

Thesis (Ph.D.)--University of Western Australia, 2006.