Biology Commons^™

Role Of Pseudomonas Produced Hydrogen Cyanide In Biological Control Of Plant-Parasitic Nematodes, Haytham Aly

Dissertations

Plant-parasitic nematodes are among the most devastating pests world-wide, causing extensive damage to important agriculture crops. The management of nematodes is challenging. Current methods used for nematode control rely mostly on using chemical nematicides and naturally resistant plants. Because of serious health and environmental problems associated with chemical control and over use of resistant plants resulting in resistant breaking strains of nematodes, alternative nematode-control methods are needed. Several potential nematode-biocontrol agents, including bacteria and fungi, have been studied for their antagonistic effect toward plant-parasitic nematodes. However, a concise picture about the biological agent’s mechanisms used to antagonize nematodes remains elusive. …

Effects Of The Exotic Shrub Lonicera Maackii On The Plant Animal Interactions In The Invaded Habitat, Humberto De Paula Dutra

Dissertations

Invasive plants are an economical, political, social, and ecological problem. Some invasive species are a serious concern for society because some of them are diseases, some are agricultural pests, and some become major threats to the ecosystems. Most studies with invasive species are limited because they measure only the impact of the invasion via direct pathways. Unfortunately, the potential for non-native plant species to alter ecosystem functions via indirect pathways mediated by interactions with animals just recently became broadly recognized. This research investigates the interactions of Amur honeysuckle with native fauna and how these interactions indirectly affect other trophic levels …

Elucidating Matrix Protein Import And Beta-Oxidation Pathways In Plant Peroxisomes, Bibi Rafeiza Khan

Dissertations

Plant peroxisomes function in fatty acid β-oxidation, jasmonic acid (JA) synthesis, and conversion of indole-3-butyric acid (IBA) to indole-3-acetic acid (IAA). Peroxisomes lack genetic material; proteins required for peroxisomal processes are imported posttranslationally. The PEX5 and PEX7 receptors import proteins containing one of two peroxisomal targeting signals (PTS1 or PTS2). I took a genetic approach to better understand protein import and to elucidate the role of Acyl-CoA Oxidase (ACX) enzymes in the model plant Arabidopsis thaliana. ACX enzymes catalyze the first step in β-oxidation. There are six ACX genes in Arabidopsis and each ACX enzyme acts on specific chain-length targets, …

Movement Ecology Of An Intercontinental Migratory Bird During Spring Stopover, Emily Beth Cohen

Dissertations

Movement ecology is a component of nearly all aspects of animal behavior and an animal’s decision to move is likely influenced by a complex combination of exogenous and endogenous factors. Therefore, an examination of the causes and consequences of organismal movement provides a conceptual framework for understanding complex behavioral strategies. My dissertation research is focused on the movement ecology of an intercontinental migratory songbird during spring migration. I adopted experimental approaches to study the factors influencing how a songbird migrant, red-eyed vireos (Vireo olivaceus), makes decisions in unfamiliar landscapes from the initiation of spring stopover.

I simulated the …

Functional Characterization Of Putative Non-Specific Phospholipase C (Npc) In Arabidopsis Thaliana, Carlotta Antonetta Peters

Dissertations

Abstract Phospholipases are enzymes that hydrolyze phospholipids. In terms of the position of bond hydrolysis, phospholipases are classified into four major types: phospholipase C (PLC), phospholipase D (PLD), phospholipase A1 (PLA1) and phospholipase A2 (PLA2). PLC hydrolyzes phospholipids at the first phosphodiester bond, producing diacylglycerol (DAG) and a phosphorylated head group. Based on substrate specificity, PLC is divided into two distinctively different groups: phosphoinositide-specific phospholipase C (PI-PLC) and non-specific phospholipase C (NPC). There are six members of the NPC family in Arabidopsis, designated NPC1 through 6 that bears sequence homology to bacterial phosphatidylcholine hydrolyzing PLC (PC-PLC). However, their function remains …

Understanding The Origin And Rapid Diversification Of The Genus Anthurium Schott (Araceae), Integrating Molecular Phylogenetics, Morphology And Fossils, Monica Maria Carlsen

Dissertations

Anthurium is a strictly neotropical genus of Araceae ranging from southern Mexico to northern Argentina, including ca. 900 species and displaying an enormous variation in leaf morphology, growth habit, leaf venation pattern and inflorescence and fruit colors. Despite its immense diversity, its ecological importance in Neotropical forests, and a very long history of botanical collection, cultivation, and taxonomical research, Anthurium had been almost neglected in molecular phylogenies. This study combines chloroplast (trnG intron, trnH-psbA and trnC-ycf6 intergenic spacers) and nuclear (CHS first intron) DNA sequence data for 102 Anthurium species and uses maximum parsimony, likelihood and Bayesian phylogenetic analysis to …

The Relations Among Laterality, Cortisol, And Approach-Avoidance Behavior In Garnett's Bushbaby (Otolemur Garnettii), David Burton Hanbury

Dissertations

Many studies to date have demonstrated that approach and avoidance behaviors are processed asymmetrically in the brain and may be reflected in measures such as handedness. The purpose of this study was to extend work in primates on this topic to Garnett’s bushbaby, a prosimian species. Furthermore, to determine whether measures in addition to handedness relate to approach-avoidance behavior, lateralized differences in tympanic membrane temperature were assessed. Cortisol measures were also obtained to determine whether it was related approach-avoidance behavior and handedness. Eleven captive-born Garnett’s bushbabies (Otolemur garnettii) were evaluated for handedness and responsiveness to novelty. Moreover, the …

Transcriptional Regulation Of Nitrogenase And Identification Of A Fructose Transport System In Anabaena Variabilis, Justin Lynn Ungerer

Dissertations

Little is known about the regulation of nitrogenase genes in cyanobacteria. Transcription of the nifH1 and vnfH genes, encoding dinitrogenase reductases for the heterocyst-specific Mo-nitrogenase and the alternative V-nitrogenase, respectively, was studied using a lacZ reporter. Two promoters were found to be responsible for expression of nifHDK; a weak promoter within nifU1 and a strong promoter upstream of nifB (the nifB1 promoter). The region immediately upstream of vnfH did not drive expression of lacZ, however the region that included the promoter for the upstream gene, ava4055 did. Characterization of the previously reported nifH1 and vnfH transcriptional start sites by 5' …

Phylogenetics And Diversification Of Escallonia (Escalloniaceae), Felipe Zapata

Dissertations

Despite a large accumulation of evidence on the high richness of plant species in the mountains of South America, little is known about the historical underpinnings of this diversity. To contribute to our understanding of the origin and diversification of plant species in these mountains, I analyzed geographic patterns of variation in molecular and phenotypic characters for the genus Escallonia L.f. (Escalloniaceae), a group of shrubs widespread in montane habitats in South America. Molecular phylogenetic analyses using chloroplast and nuclear loci revealed i) that Escallonia is monophyletic, ii) a remarkable level of geographical phylogenetic structure, and iii) a widespread absence …

Neuroprotective Effects Of A Nicotinic Acetylcholine Receptor Agonist And Modulator In The Rodent Retina, Kazuhiro Iwamoto

Dissertations

The purpose of this dissertation is to assess the potential neuroprotective effect of an alpha7 nAChR agonist, PNU-282987, and modulator, PNU-120596, in an in vitro model of excitotoxicity and an in vivo model of acute glaucoma. In in vitro studies, retinas obtained from Long Evans rats were cultured using various concentrations of the PNU compounds to analyze neuroprotection against glutamate-induced excitotoxicity. After 3 days in culture, RGCs were identified using an antibody against Thy 1.1, visualized using a fluorescent dye and quantified. In culture, glutamate significantly decreased the number of RGCs. However, if either PNU compound was introduced before the …

Molecular, Cellular And Systemic Effects Of Atrazine On The Xenopus Laevis Tadpole, Renee Maryanne Zaya

Dissertations

Atrazine is one of the two most commonly used herbicides in the US and it is the most studies are among the first to link physiological effects of atrazine to changes in tissue and gene expression in Xenopus laevis tadpoles. These studies provide the groundwork for future studies into the mechanisms behind responses to chemical stressors generating data resulting in a better understanding of how these chemicals affect us all. commonly found herbicide in ground water. As a result, a great deal of attention has been placed on its use and safety. It has also been implicated to play a …