Doctor of Philosophy, The Ohio State University, 1985, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Doctor of Philosophy, The Ohio State University, 1958, Graduate School

Committee: Not Provided (Other) Subjects: Health Sciences

Doctor of Philosophy, The Ohio State University, 1959, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Doctor of Philosophy (PhD), Ohio University, 2008, Molecular and Cellular Biology (Arts and Sciences)

Plants with both open, out-crossing chasmogamous and closed, self-pollinating cleistogamous flowers are distributed over 50 angiosperm families. The chasmogamous-cleistogamous mixed breeding system is a successful reproductive strategy because it can ensure seed output over a range of environmental and pollinator conditions and maintain sexually produced progeny even in the absence of pollination agents. Many ecologists and biologists have conducted research on the mixed breeding system, but the underlying molecular mechanisms remain largely unknown. The research presented here examined the molecular biology of flower development in a widespread North American violet, Viola pubescens. The plant growth regulator gibberellic acid (GA) was reported to induce chasmogamous flowers from cleistogamous ones in some species. Two genes, VGA20ox and VGA3ox, which encode key enzymes (GA20 oxidase and GA3 oxidase) in the biosynthesis of GA, were identified by reverse transcriptase polymerase chain reactions (RT-PCR) from V. pubescens. Semi-quantitative RT-PCR indicated that both genes exhibited increased expression in chasmogamous flowers compared to cleistogamous flowers. Exogenous application of GA3, however, did not induce cleistogamous flowers to open. Thus, GA is involved in the mixed breeding system, but it is not sufficient to convert the closed status of cleistogamous flowers in V. pubescens. GA was demonstrated to target the floral meristem identity gene LEAFY (LFY) in Arabidopsis. Two LFY orthologs (VLFY1 and VLFY2) were obtained by screening a genomic library of V. pubescens. Semi-quantitative RT-PCR suggested the two LFY orthologs function together in the early stages of development of both flower types. Analysis of their promoters indicated they might be differentially regulated. The ABCE floral organ identity genes come into play once the floral meristems are determined. Two A class genes (VAP1 and VAP2), two B class genes (VAP3 and VPI), one C class gene (VAG) and (open full item for complete abstract)

Committee: Sarah E. Wyatt (Advisor); Ballard E. Harvey Jr. (Advisor); Showalter Allan (Committee Member); Susan Evans (Committee Member) Subjects: Biology; Botany; Molecular Biology

Master of Science (MS), Ohio University, 2003, Plant Biology (Arts and Sciences)

The enzyme invertase contributes to sugar unloading, pathogen defense,differentiation and development in plants. One soluble invertase cDNA was cloned using RACE in this study. Its sequence structure and its sequence similarity to that of other invertases suggest that the full-length 2237bp cDNA (PsI-1 cDNA), represents a functional vacuolar invertase. It is strongly expressed in sink organs such as young stem,root tip, and flower buds. Its expression is up-regulated by GA. Two genomic clones(clone 8 and clone 4) were identified. Clone 8 is believed to contain the PsI-1 gene based on sequence similarity. The presence of an array of potential cis-acting elements in the 5'upstream sequence of PsI-1 suggest that its expression can be adjusted to suit a variety of developmental and environmental needs. Comparison of sequence similarities and gene structure suggests that the invertase-homologous sequence in clone 4 may have originated from an invertase gene/pseudogene different from PsI-1.

Committee: John Mitchell (Advisor) Subjects: Biology, Plant Physiology