Clitellate annelids display conserved mechanisms of segmental ectodermal and mesodermal patterning. These tissues are generated by asymmetric divisions of large stem cells called teloblasts, elongating the ectoderm and mesoderm of the embryo. Each teloblast-derived lineage makes highly stereotyped contributions to the leech: the N, O, P, and Q contribute specific neurons, epidermis, and other ectodermal tissues along the ventral-to-dorsal axis of the embryo, respectively. The N and Q ectodermal lineages appear to be specified autonomously, but specification of the O and P lineages depends upon interactions with other, neighboring teloblast lineages. Until quite recently, there have been precious few teloblast lineage-specific markers, and virtually no molecular candidates for genes influencing the proper differentiation of any of these lineages. Here, I explore the possibility that members of the Pax-Six-Eyes absent-Dachshund network are involved in leech ectodermal patterning. I show that the leech Helobdella sp. Austin has two Pax6 paralogs, and demonstrate that Hau-Pax6A is expressed early in a subset of N-derived cells and O-derived cells. Next, I demonstrate that an ortholog of the six gene family, Hau-six1/2a, is expressed in the P lineage. I show through a series of cell ablations that Hau-six1/2a expression is regulated by neighboring teloblasts in a manner consistent with P fate induction, hinting that this transcription factor may be involved in P specification. The identification of these genes is a first step towards dissecting the molecular mechanisms of ectodermal teloblast differentiation in the leech embryo. The evolutionary context of the deployment of these genes is also discussed. In the appendices, I present two projects on the evolution of pigment patterns in Danio rerio and its relatives. In the first, I show that the larval melanin-containing pigment cells of Danio nigrofasciatus are uniquely redeployed into the adult pigment pattern, in contrast to seven related fishes. In the second, I show that variation in yellow pigment cell populations in different danio species may be dependent on variable signaling through the receptor tyrosine kinase fms pathway. / text

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.