Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 111-113). Available also in a digital version from Dissertation Abstracts.

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Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Stanley J. Roux, Jr. Vita. Includes bibliographical references.

The life cycle of land plants alternates between the haploid gametophyte and the diploid sporophyte generations. Asexual reproductive strategies, that bypass meiosis and fertilization, have evolved in diverse land plant taxa. Apogamy is one such strategy that produces a sporophyte directly from a gametophyte cell. The genes that drive the process of apogamy are unknown. Knowledge of these genes and their functions will provide insight into the evolution of asexual reproduction, the sporophyte body plan and the alternation of generations in land plants. My Ph. D. research has focused on identifying the genes function in apogamy commitment, and understanding the functions of their counterparts in angiosperms. First, I successfully induced apogamy from the fern Ceratopteris richardii and discovered that the gametophytes begin to become committed to apogamy after 10 days of culture on inductive medium. I then created a cDNA library that represents genes with enhanced expression during commitment. Comparison of the Gene Ontology terms mapped to this cDNA library with that of the gametophyte transcriptome of the fern Pteridium aquilinum showed that this library is enriched in genes that function in stress response and metabolism. This library contains many sequences whose homologues in Arabidopsis are specifically expressed or upregulated in flower organs or seed structures, both of which are absent in ferns. One of these genes, UNC93-like, is expressed in the eggs of C. richardii gametophytes, as evidenced by in situ hybridization. Functional egg cells are implicated as necessary for C. richardii gametophytes to undergo apogamy. In Arabidopsis, an AtUNC93-like mutant, which produces a partial AtUNC93-like transcript, has vegetative and reproductive defects. Embryo abortion and gametophyte lethality contribute to a small seed set in these plants. Reciprocal crosses indicate that the mutant allele does not affect gametophyte function but cause a maternal failure to maintain viability of all gametophytes. Thus, the AtUNC93-like gene is necessary for normal sporophyte vegetative growth and reproductive success, but is dispensable for the direct function of gametophytes. My research has provided insight into the mechanisms that induce apogamy in a fern. The apogamy library is a valuable resource for future investigations into apogamy.

Spores from a weakly salt tolerant strain of Ceratopteris richardii containing the mutation stl1 were irradiated and sown on nutrient medium supplemented with 200 m M NaCl. A single highly salt tolerant gametophyte was recovered and selfed to generate a homozygous sporophyte. Spores from this strain, 10α23, were used to document the sexual transmission of the trait and to monitor the inheritance of tolerance in crosses to both the wild type and to the parental salt tolerant strain. Genetic analysis showed the 10α23 strain to possess both the original stl1 mutation and an additional semi-dominant nuclear mutation, stl2, that individually conferred a high level of tolerance to gametophytes. In combination, both mutations had additive effects. Tolerance was also evident in sporophytes, but at a lower level than in gametophytes.

The life cycle of all land plants is characterized by the alternation between two multicellular generations: haploid gametophytes and diploid sporophytes. Whereas meiotic recombination and fertilization via sexual reproduction is known to confer adaptive evolutionary benefits, some plant species can reproduce asexually bypassing meiosis and fertilization yet still undergo alternation of generations. In ferns, the two asexual reproductive pathways are termed apogamy and apospory, i.e. the asexual reproduction of sporophytes and gametophytes, respectively. Although understanding the process of asexual reproduction in flowering plants would be of considerable agricultural value, the molecular mechanisms underlying this process have yet to be identified. Similarly, the genes in ferns that underlie apogamy and apospory are unknown. Knowledge of such genes will provide invaluable information not only for the evolutionary study of asexual reproduction in land plants, but also insight into the developmental program for each generation. My PhD research focuses on the investigation of candidate genes involved in asexual reproduction in the model fern Ceratopteris richardii. Though the molecular mechanisms underlying asexual reproduction are not understood, it is hypothesized that asexual reproduction is the result of altered regulation of certain sexual reproduction-related genes. Therefore, I selected candidate genes for asexual reproduction in C. richardii, CrEMS1, CrKNOX3 and CrANT, based on the functions of their respective homologs during sexual reproduction in two other model systems: Arabidopsis thaliana and Physcomitrella patens. I showed that, in C. richardii, CrEMS1 is expressed during key events of sexual reproduction, including sporogenesis, gametogenesis and embryo development; CrKNOX3 expression is specific for the mature egg cells and CrANT expression is restricted to sperm cells. The presence of CrEMS1 during early embryo development made it a suitable candidate for an embryonic marker for future research. To study the function of the candidate genes, I overexpressed CrKNOX3 and BnBBM, a flowering plant BBM gene that has similar expression patterns in Brassica to CrANT. The overexpression of CrKNOX3 results in unique cell outgrowth from the antheridia, and overexpression of BnBBM results in spontaneous apogamy induction. Whole mount in situ also showed CrEMS1 expression, marking embryonic identity, in pre-apogamous cells undergoing sugar-induced and overexpression of BnBBM-induced apogamy. The results of my PhD research provides, for the first time, insight into the molecular mechanisms underlying asexual reproduction in the model fern C. richardii, and invaluable tools, transient and stable Agrobacterium-mediated transformation protocols, for functional genomics research in this fern. The spontaneous apogamy induction on BnBBM-expressing gametophytes and the presence of CrEMS1 in pre-apogamous cells confirm the hypothesis that asexual reproduction is the result of the alteration in expression of sexual-related genes, verifying that the two pathways share a common set of genes.

O aerênquima é um tecido vegetal com grandes lacunas de ar que podem ter função de circulação de gases e/ou sustentação de órgãos, estando presente nas raízes e órgãos aéreos de plantas aquáticas ou sob alagamento, podendo ainda ser formado em decorrência de algum estresse. Ceratopteris richardii é uma planta aquática, de hábito anfíbio que apresenta aerênquima em seus órgãos vegetativos. Dessa forma, esse trabalho buscou analisar a formação de aerênquima nas raízes e pecíolo desta espécie frente a uma situação de restrição hídrica e verificar sua plasticidade fenotípica. Vinte indivíduos de C. richardii foram cultivados e submetidos a um tratamento com diferentes concentrações de PEG 6000. Em todas as amostras analisadas, foi observada a formação de aerênquima. A análise qualitativa mostrou diferença entre os tratamentos, porém, a análise estatística revelou que as diferenças não são significativas para o número amostral empregado. Variações de crescimento do esporófito revelaram que a espécie de estudo modificou algumas características de desenvolvimento em resposta a restrição hídrica. Tais resultados revelam importantes características para esta espécie, que parece aclimatar-se a situação de estresse a qual foi submetida. Com base nisso, sugere-se ampliar estes estudos para elucidar questões relacionadas a formação de aerênquima e o ambiente, seja para esta espécie ou de outro grupo taxonômico. / Aerenchyma is a plant tissue with large air gaps that may have gas circulation function and / or sustain organs. This structure is present in roots and aerial organs of water plants and in plants under flooding it may also be formed during some stress. Ceratopteris richardii is an aquatic plant, with amphibious habit that has aerenchyma in their vegetative organs. Thus, the aim of this study is analyze the aerenchyma formation in roots and stem of this specie under water restriction situation and verify their phenotypic plasticity. Twenty specimen of C. richardii were cultured and subjected to treatment with different concentrations of PEG 6000. In all samples, were observed aerenchyma formation. Qualitative analysis showed differences among treatments, however, the statistical analysis revealed that the differences are not significant for the sample size. Sporophyte growth variations revealed that the specie of study modified some growth characteristics in response to water restriction. These results reveal important characteristics for C. richardii, which seems to acclimatize the stress situation which has submitted. On the base that, it is suggested further studies to become clearer the relation between aerenchyma formation and environment, even to either this species or another taxonomic group.

O aerênquima é um tecido vegetal com grandes lacunas de ar que podem ter função de circulação de gases e/ou sustentação de órgãos, estando presente nas raízes e órgãos aéreos de plantas aquáticas ou sob alagamento, podendo ainda ser formado em decorrência de algum estresse. Ceratopteris richardii é uma planta aquática, de hábito anfíbio que apresenta aerênquima em seus órgãos vegetativos. Dessa forma, esse trabalho buscou analisar a formação de aerênquima nas raízes e pecíolo desta espécie frente a uma situação de restrição hídrica e verificar sua plasticidade fenotípica. Vinte indivíduos de C. richardii foram cultivados e submetidos a um tratamento com diferentes concentrações de PEG 6000. Em todas as amostras analisadas, foi observada a formação de aerênquima. A análise qualitativa mostrou diferença entre os tratamentos, porém, a análise estatística revelou que as diferenças não são significativas para o número amostral empregado. Variações de crescimento do esporófito revelaram que a espécie de estudo modificou algumas características de desenvolvimento em resposta a restrição hídrica. Tais resultados revelam importantes características para esta espécie, que parece aclimatar-se a situação de estresse a qual foi submetida. Com base nisso, sugere-se ampliar estes estudos para elucidar questões relacionadas a formação de aerênquima e o ambiente, seja para esta espécie ou de outro grupo taxonômico. / Aerenchyma is a plant tissue with large air gaps that may have gas circulation function and / or sustain organs. This structure is present in roots and aerial organs of water plants and in plants under flooding it may also be formed during some stress. Ceratopteris richardii is an aquatic plant, with amphibious habit that has aerenchyma in their vegetative organs. Thus, the aim of this study is analyze the aerenchyma formation in roots and stem of this specie under water restriction situation and verify their phenotypic plasticity. Twenty specimen of C. richardii were cultured and subjected to treatment with different concentrations of PEG 6000. In all samples, were observed aerenchyma formation. Qualitative analysis showed differences among treatments, however, the statistical analysis revealed that the differences are not significant for the sample size. Sporophyte growth variations revealed that the specie of study modified some growth characteristics in response to water restriction. These results reveal important characteristics for C. richardii, which seems to acclimatize the stress situation which has submitted. On the base that, it is suggested further studies to become clearer the relation between aerenchyma formation and environment, even to either this species or another taxonomic group.

O aerênquima é um tecido vegetal com grandes lacunas de ar que podem ter função de circulação de gases e/ou sustentação de órgãos, estando presente nas raízes e órgãos aéreos de plantas aquáticas ou sob alagamento, podendo ainda ser formado em decorrência de algum estresse. Ceratopteris richardii é uma planta aquática, de hábito anfíbio que apresenta aerênquima em seus órgãos vegetativos. Dessa forma, esse trabalho buscou analisar a formação de aerênquima nas raízes e pecíolo desta espécie frente a uma situação de restrição hídrica e verificar sua plasticidade fenotípica. Vinte indivíduos de C. richardii foram cultivados e submetidos a um tratamento com diferentes concentrações de PEG 6000. Em todas as amostras analisadas, foi observada a formação de aerênquima. A análise qualitativa mostrou diferença entre os tratamentos, porém, a análise estatística revelou que as diferenças não são significativas para o número amostral empregado. Variações de crescimento do esporófito revelaram que a espécie de estudo modificou algumas características de desenvolvimento em resposta a restrição hídrica. Tais resultados revelam importantes características para esta espécie, que parece aclimatar-se a situação de estresse a qual foi submetida. Com base nisso, sugere-se ampliar estes estudos para elucidar questões relacionadas a formação de aerênquima e o ambiente, seja para esta espécie ou de outro grupo taxonômico. / Aerenchyma is a plant tissue with large air gaps that may have gas circulation function and / or sustain organs. This structure is present in roots and aerial organs of water plants and in plants under flooding it may also be formed during some stress. Ceratopteris richardii is an aquatic plant, with amphibious habit that has aerenchyma in their vegetative organs. Thus, the aim of this study is analyze the aerenchyma formation in roots and stem of this specie under water restriction situation and verify their phenotypic plasticity. Twenty specimen of C. richardii were cultured and subjected to treatment with different concentrations of PEG 6000. In all samples, were observed aerenchyma formation. Qualitative analysis showed differences among treatments, however, the statistical analysis revealed that the differences are not significant for the sample size. Sporophyte growth variations revealed that the specie of study modified some growth characteristics in response to water restriction. These results reveal important characteristics for C. richardii, which seems to acclimatize the stress situation which has submitted. On the base that, it is suggested further studies to become clearer the relation between aerenchyma formation and environment, even to either this species or another taxonomic group.

Understanding the movement behavior and foraging strategies of individuals across multiple spatial and temporal scales is essential not only for understanding the biological requirements of individuals but also for linking individual strategies to population level effects. Glacial fjords scattered throughout south-central and southeastern Alaska host some of the largest seasonal aggregations of harbor seals (Phoca vitulina richardii) in the world, and an estimated 15% of the harbor seal population in Alaska is found seasonally at these glacial ice sites. Over the last two decades, the number of harbor seals has declined at two of the primary glacial fjords, in Aialik Bay in south-central Alaska and in Glacier Bay in southeastern Alaska, thus raising concerns regarding the viability of seal populations in glacial fjord environments. From 2004-2009, the foraging ecology, diving behavior, and migration patterns of harbor seals from Glacier Bay National Park, Alaska were examined in relation to prey availability and oceanographic features in Glacier Bay and the surrounding regions of southeastern Alaska. Time-depth recorders, very high frequency transmitters, and satellite-linked transmitters were used to quantify the vertical and horizontal movement patterns of harbor seals in the marine environment. Specifically, (1) I characterized the diving behavior, foraging areas, and foraging strategies of female harbor seals from terrestrial and glacial ice sites relative to prey availability during the breeding season (May-June) in Glacier Bay, (2) I quantified the intra-population variation in at-sea post-breeding season (September-April) distribution and movement patterns of female harbor seals in relation to oceanographic features, (3) I quantified the post-breeding season migration patterns of female harbor seals relative to the boundaries of the marine protected area of Glacier Bay National Park, and (4) I characterized the use of the continental shelf region of the eastern Gulf of Alaska by female harbor seals from Glacier Bay, both as a foraging area and as a migratory corridor in relation to oceanographic features. During the breeding season, there was a substantial degree of intra-population variation in the diving behavior and foraging areas of juvenile and adult female seals from glacial ice and terrestrial sites in Glacier Bay. The presence of multiple diving strategies suggests that differences in the relative density and depth of prey fields in glacial ice and terrestrial habitats in addition to seal age and reproductive status may influence diving and foraging behavior of harbor seals. During the post-breeding season, juvenile and adult female harbor seals ranged extensively beyond the boundaries of the marine protected area of Glacier Bay National Park, throughout the northern inshore waters of southeastern Alaska and the continental shelf region of the eastern Gulf of Alaska between Cross Sound and Prince William Sound, Alaska (up to 900 kilometers away). Seals exhibited a relatively high degree of intra-population variation in their at-sea post-breeding season distribution patterns that may be a function of extrinsic factors such as oceanographic characteristics, which can influence prey availability as well as intrinsic factors including previous experience with foraging areas and seal condition and age. Use of the continental shelf region of the eastern Gulf of Alaska by harbor seals as a foraging area may be due to enhanced biological productivity which may be associated with ephemeral hydrographic and/or static bathymetric features. Despite extensive migrations of seals from Glacier Bay during the post-breeding season, there was a high degree of inter-annual site fidelity of seals to Glacier Bay the following breeding season after seals were captured. / Graduation date: 2012