published_or_final_version / abstract / toc / Zoology / Master / Master of Philosophy

published_or_final_version / abstract / toc / Surgery / Master / Master of Philosophy

To identify a model legume experimental system for studying low temperature signaling and cold acclimation, cold-induced expression and regulation of homologues of alfalfa (Medicago sativa) cold acclimation-specific genes cas15 and cas30 were examined in M. arborea (relatively frost tolerant) and M. truncatula (relatively frost sensitive). Both cas15 and cas30 genes are present in the genomes of both species but whereas both genes are cold-induced in M. arborea, only cas15 is induced in M. truncatula. Cold-induced expression of these genes is inhibited by calcium chelators and channel blockers and by the membrane fluidizer benzyl alcohol. Treatment of leaves with dimethylsulfoxide, a membrane rigidifier, induced both genes at 25°C. A cold-activated MAP kinase activity was expressed in both species. These results suggest that M. truncatula, an annual, self-pollinated species may be successfully used as model experimental systems in studies of cold signaling and role of cas genes in cold acclimation in legumes.

Thesis (Ph. D.)--University of Missouri--Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves : 131-150). Also available on the Internet.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Biological Sciences, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri--Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 123-133). Also issued on the Internet.

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 70 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 63-68).

Title from second page of PDF document. Includes bibliographical references (p. Xx-Xx).

A principal fonte de proteínas para alimentação humana e animal é fornecida pelas sementes de cereais e leguminosas. O conteúdo de aminoácidos solúveis em endospermas de milho normal e mutantes opaco-2 e floury foram determinadas por HPLC. A análise indicou que a concentração total de aminoácidos solúveis variou entre os mutantes e seus tipos selvagens. Nos mutantes o10, o11 e o13, as concentrações foram aumentadas significativamente quando comparadas ao tipo selvagem W22, enquanto os mutantes o1, o2, o13, fl1 e fl2 exibiram baixas concentrações em relação ao seu respectivo tipo selvagem Oh43. Resultados similares foram obtidos para os mutantes o5, o7 e fl3 em relação aos seus tipos selvagens (B79, B37 e WT3, respectivamente). Para metionina, o mutante o2 e o tipo selvagem Oh43 apresentaram as mais altas concentrações deste aminoácido. Diferenças significativas não foram observadas para os outros aminoácidos analisados, tais como lisina e treonina. Os resultados sugerem que as altas concentrações sugeridas originalmente para estes mutantes devem ser devidas aos níveis destes aminoácidos incorporados nas proteínas de reserva, mas não na forma solúvel. / For human nutrition the main source of vegetable proteins are cereal and legume seeds. The content of total soluble amino acids in mature endosperms of wildtype and maize opaque and floury mutants have been determined by HPLC. The total absolute concentration of soluble amino acids among the mutants and their wild-type counterparts varied depending on the mutant. In the o10, o11 and o13 mutants the concentrations were significantly increased when compared to their wild-type counterpart W22, whereas the mutants o1, o2, o13, fl1 and fl2 exhibited lower concentrations when compared to the wild-type Oh43, Similar results were observed for o5, o7 and fl3 in relation to their specific wild-type counterparts (B79, B37 and WT3, respectively). For soluble methionine content, o2 and Oh43 exhibited the highest concentrations. Significant differences were not observed for other amino acids such as lysine and threonine. The results suggest that the high-lysine concentrations indicated originally for these mutants must be due to the amino acids incorporated into storage proteins, but not in the soluble form.

This thesis investigates the effect of Russian wheat aphid (RWA; Diuraphis noxia) infestation on the defence responses of the bread wheat line, PI 137739, on a molecular level. PI 137739 is known to contain the RWA resistance gene, Dn1. The study was conducted by utilising and combining a vast array of molecular biological techniques. Chapter 1 introduces the reader to a summary of the resistance responses observed within infested plants. A detailed description of the Russian wheat aphid follows and the genes responsible for RWA resistance in wheat is discussed. A brief report of research performed on the bread wheat genome is given and the biochemical defence responses of plants against insect infestation are discussed. This is followed by a concise description of resistance (R) genes and resistance gene categories in plants. The last discussion concerns microarray technology, a molecular tool utilised during this study. Chapter 2 aims at identifying genes involved in resistance against RWA infestation; specifically, genes containing the conserved nucleotide binding site¬leucine rich repeat (NBS-LRR) motif. Genomic, as well as complementary DNA (cDNA), was utilised in order to compare functional gene expression in wheat infested with the RWA. This was executed by employing PCR-based methods, single-pass sequencing and basic local alignment search tool (BLAST) analyses. Chapter 3 introduces suppression subtractive hybridisation (SSH) as a tool to further identify NBS-LRR or other resistance-related sequences in RWA infested wheat plants. SSH allows the comparative analysis of differential gene expression in RWA infested and uninfested wheat in order to identify resistance-¬related genes expressed in the infested, resistant wheat plants. The effect of RWA infestation on wheat resistance responses was examined further in chapter 4 through microarray analysis. The aim was the introduction and establishment of the microarray technique and to test the feasibility of using microarrays for differential gene expression and regulation studies. Microarray slides were assembled in order to monitor the up- and down¬regulation of genes at different time intervals - day 2, day 5 and day 8 - of RWA infestation. Clones isolated throughout this study were assembled on microarray slides and probed with control and RWA infested RNA. Differential gene regulation was assessed and further confirmed through Northern blot analyses, as well as quantitative real-time PCR. The thesis concludes with a general summary of the results obtained in chapter 5 and future prospects are outlined. / Thesis (PhD(Genetics))--University of Pretoria, 2005. / Genetics / unrestricted