Evolution of developmental genes is an important mechanism for plant morphological evolution. The LRL genes are an ancient group of bHLH transcription factors that positively regulate root hair development in angiosperms. Here I show that, in the moss Physcomitrella patens, two LRL genes are present and they positively regulate rhizoid and caulonema (a rhizoid-like cell type) development. GUS-transcriptional reporter plants show that both PpLRL1 and PpLRL2 are expressed in tissues giving rise to caulonemata. Loss-of-function mutants in either PpLRL1 or PpLRL2 led to defective rhizoid and caulonema development, and the Pplrl1 Pplrl2 double loss-of-function mutants completely lack rhizoids and caulonemata. Consistent with this, gain-of-function mutants show enhanced rhizoid and caulonema development. In addition, I show that the stimulatory effects of auxin and low phosphate on the development of rhizoids and/or caulonemata required PpLRL gene function. Together, these results show that LRL genes are conserved, positive regulators in tip-growing rooting cell development in land plants. To elucidate whether LRL genes belong to part of a conserved gene network, I use qRT-PCR to determine the transcriptional interaction between LRL genes and the Class I RSL genes, which is another group of conserved regulators of rhizoids and root hairs. Comparing the LRL-RSL network between P. patens and A. thaliana reveals that LRL and Class I RSL genes are transcriptionally independent of each other in P. patens but one LRL gene is transcriptionally downstream of Class I RSL genes in A. thaliana. This suggests that the gene network controlling tip-growing rooting cell development has changed since mosses and angiosperms last shared a common ancestor.

published_or_final_version / abstract / toc / Biochemistry / Master / Master of Philosophy

Those epiphytes which are inhabited by ants are reviewed; they comprise nine genera in four families. All are tropical and most are from the Far East. They probably all gain mineral nutrients from material brought by the ants. This contrasts with myrmecophytic trees and shrubs which are defended against insect herbivores by ants collecting food produced by the plant. five of the nine genera of ant-epiphytes belong to the Rubiaceae; two of these, Hydnophytum and Myrmecodia are highly diversified and specialized. They are found throughout the tropical Far East in a range of habitats, but are most abundant in open canopies. Ants (Iridomymex cordatus and I. cf. scrutator) occupy cavities in the enlarged hypocotyl. The 'tuber' cavities and other unusual morphological features are elaborated in Myrmecodia. For instance, spines of different types are derived from adventitious roots; internodes are condensed and covered by outgrowths at each leaf-base; stipules are enlarged and differ in their splitting. The inflorescence rachis is progressively reduced in Hydnophytum, and the flowers sunk in the stem in Myrmecodia. These structural changes possibly benefit the ants, but may have reduced the frequency of crosspollination, though some heterostyly is present. The morphology of the satellite genera (Myrrnephytum, Anthorhiza and Squamellaria) shows some parallels with that of Myrmecodia. The five genera are united as a subtribe - the Hydnophytinae. Detailed taxonomic treatment of Myrmecodia and the satellite genera, but not Hydnophytum, is given. Myrmecodia is reduced from 43 to 18 species. One is a variable, widespread, lowland species which is divided into informal categories. One is polytypic with three subspecies, four are variable, but not divided, and the rest are monotypic, geographically restricted, mostly montane species. The pattern of variation is often reticulate, and a hierarchy or infrageneric grouping was not identified. Myrmecodia and the satellite genera appear to have evolved independently from Hydnophytum-like ancestors. Structures probably advantageous to the ants have arisen repeatedly, but may also have led to inbreeding and taxonomic difficulty. The more sophisticated symbiosis in Myrmecodia may be reflected by the more mesomorphic nature of that genus, and is a prime example of coevolution between higher plants and animals.

Florida’s sea turtle populations are increasing due to conservation efforts; however, sea turtle species are vulnerable to climate change. Turtles exhibit temperaturedependent sex determination, in which nest environment influences sex. Environmental changes may produce altered sex ratios that limit reproduction potential; therefore hatchling sex ratios should be monitored. Hatchlings are not externally sexually dimorphic, making sex identification difficult. This study established baseline plasma hormone concentrations in hatchling and post-hatchling green (Chelonia mydas) and loggerhead (Caretta caretta) sea turtles using High Performance Liquid Chromatography. Five hormones were assayed and were present in the majority of samples (testosterone: N.D.-10.12, progesterone: N.D.-0.43, estradiol: N.D.-4.78, estriol: N.D.-5.55 and estrone: N.D.-1.67 μg/mL). Plasma hormones did not distinguish hatchling sex because male and female ranges overlapped. Hormone concentrations varied with sex but also with incubation temperature, indicating that climate change could impact hatchling and posthatchling hormone profiles and thus could impact future fitness. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

The Annual Killifish, Austrofundulus limnaeus, survives the seasonal drying of their pond habitat in the form of embryos entering diapause midway through development. The diapause trajectory is one of two developmental phenotypes. Alternatively, individuals can "escape" entry into diapause and develop continuously until hatching. The alternative phenotypes of A. limnaeus are a form of developmental plasticity that provides this species with a physiological adaption for surviving stressful environments. The developmental trajectory of an embryo is not distinguishable morphologically upon fertilization and phenotype is believed to be influenced by maternal provisioning within the egg based on observations of offspring phenotype production. However, incubation temperature may override any such maternal pattern suggesting an environmental influence on the regulation of developmental trajectory. We hypothesize that maternally packaged gene products coordinate the cellular events prior to the maternal-to-zygotic transition (MTZ) that determine developmental trajectory in embryos of A. limnaeus. In addition, we propose that environmentally responsive gene expression after the MTZ can sustain or override any such maternal provisioning. Using high-throughput RNA-sequencing, we have generated transcriptomic profiles of protein-coding messenger RNA and noncoding RNA during development in A. limnaeus. Embryos destined for either the diapause or escape phenotypes display unique expression profiles immediately upon fertilization that support hormone synthesis, well before the stage when phenotypes are morphologically distinct. At stages when the trajectories diverge from one another, differential expression of the vitamin D receptor signaling pathway suggests that vitamin D signaling may be a key regulator of developmental phenotype in this species. These data provide a critical link between maternal and environmental influences on the genetic regulation of phenotypic plasticity. These results will not only impact our understanding of the genetic mechanisms that regulate entrance into diapause, but also provide insight into the epigenetic regulation of gene expression and development. Uncovering genetic mechanisms in a system exhibiting alternative developmental trajectories will elucidate the role of maternal packaging in regulating developmental decisions, and in sustaining metabolic depression during diapause.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 201-225). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 201-225). Also available on the Internet.

Copies of author's previously published articles inserted. / Bibliography: leaves 117-130. / v, 130, [51] leaves, [33] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The general aim of this thesis is to develop methods for the identification of markers for pluripotent cell subpopulations in the developing mouse embryo. A screen for mouse embryonic stem (ES) cell markers is carried out, to identify transcripts that are differentially expressed between ES cells and X cells, and to investigate pluripotent cell heterogeneity during early development. The study demonstrates the potential to identify and characterise molecular heterogeneity within the developing pluripotent cell pool in vivo, via the controlled progression and analysis of pluripotent cells in vitro. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1997

Thesis (M.Sc.)--Memorial University of Newfoundland, Faculty of Medicine, 1999. / Typescript. Bibliography: p. 115-134.

Temperature plays a crucial role in the constant interaction between organisms and the environment. It affects development and rates of physiological functions as well as survival of organisms.