Life Sciences Commons^™

A Novel Transcription Factor In Arabidopsis Thaliana Abiotic Stress Response, Achira S. Weerathunga Arachchilage

University of New Orleans Theses and Dissertations

Plants respond to environmental stress by altering their gene expression. Under stress conditions some genes are activated and some genes are repressed. Even though a lot of work has been done to understand mechanisms of gene activation under abiotic stress very little information is available on how stress responsive genes are kept repressed under normal growth conditions. Recent work has revealed that plants use transcriptional repression as common mechanism of gene repression. Transcriptional repression is achieved by recruitment co-repressor complexes to the target genes. Recent studies have revealed that the co-repressor LUH complexes with SLK1 and SLK2 to silence Arabidopsis …

Functional Analysis Of The Mir156 Regulatory Network In Arabidopsis Siliques, Zhishuo Wang

Electronic Thesis and Dissertation Repository

Siliques are photosynthetically active seed capsules and their development is strongly influenced by embryo development. MicroRNA156 (miR156)-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) network is involved in regulating plant growth and development, but the downstream genes of this network are still not fully elucidated. Here, I show that the miR156/SPL2 pathway controls the development of floral organs, regulates pollen production, and thus affects male fertility in Arabidopsis thaliana. I present evidence that SPL2 binds to the 5’UTR of the ASYMMETRIC LEAVES 2 (AS2) gene in vivo, indicating that AS2 acts downstream of SPL2. When compared to wild-type plants, AS2 loss-of-function mutants …

Characterization Of Sbip68: A Putative Tobacco Glucosyltransferase Protein And Its Role In Plant Defense Mechanisms, Abdulkareem O. Odesina

Electronic Theses and Dissertations

Plant secondary metabolites are essential for normal growth and development in plants ultimately affecting crop yield. They play roles ranging from appearance of the plants to defending against pathogen attack and herbivory. They have been used by humans for medicinal and recreational purposes amongst others. Glycosyltransferases catalyze the transfer of sugars from donor substrates to acceptors. Glucosyltransferases are a specific type of glycosyltransferases known to transfer glucose molecules from a glucose donor to a glucose acceptor (aglycone) producing the corresponding glucose secondary metabolite or glycone, in this case glucosides. It was hypothesized that SBIP68, a tobacco putative glucosyltransferase-like protein glucosylated …

Storage Of Round And Square Switchgrass Bales: Effect Of Storage Time And Fungal Inoculation On Saccharification Efficiency, Noaa Frederick

Graduate Theses and Dissertations

To produce fermentable sugars from lignocellulosic biomass feedstock, severe pretreatment conditions are needed (either high acid concentration, temperature, or retention times). High severities can produce toxic byproducts which inhibit enzymatic hydrolysis or fermentation. In order to reduce pretreatment severities (and thus increase enzyme and fermentation efficiency), the white-rot fungus Pleurotus ostreastus was seeded into square and round bales of Kanlow switchgrass (Panicum virgastum L.) and left in the field over a period of 9 month. The laccase producing fungus is believed to selectively degrade lignin, a common plant structural polymer, which can function as an enzymatic inhibitor. Samples were taken …

Rare Occurrences Of Free-Living Bacteria Belonging To Sedimenticola From Subtidal Seagrass Beds Associated With The Lucinid Clam, Stewartia Floridana, Aaron M. Goemann

Masters Theses

Lucinid clams and their sulfur-oxidizing endosymbionts comprise two compartments of a three-stage, biogeochemical relationship among the clams, seagrasses, and microbial communities in marine sediments. A population of the lucinid clam, Stewartia floridana, was sampled from a subtidal seagrass bed at Bokeelia Island Seaport in Florida to test the hypotheses: (1) S. floridana, like other lucinids, are more abundant in seagrass beds than bare sediments; (2) S. floridana gill microbiomes are dominated by one bacterial operational taxonomic unit (OTU) at a sequence similarity threshold level of 97% (a common cutoff for species level taxonomy) from 16S rRNA genes; …

Field Screening Of Diverse Soybean Cultivars For Flood Tolerance, Jane Achando Khatenje Mokua

Graduate Theses and Dissertations

Flooding can significantly reduce soybean growth, development, and yield. Therefore, screening and identification of flood-tolerant soybeans will enhance development of cultivars that are well suited for flood-prone areas. Sets of screening tests were conducted in Stuttgart, Arkansas using three separate but related experiments, with the purpose of establishing effective flood tolerance screening protocol that can identify tolerant and sensitive cultivars. Each experiment was completely randomized with three replications. The first experiment involved screening of 256 maturity group (IV and V) cultivars. Flooding was imposed at the fifth-node (V5) or first-bloom (R1) stage for ten days. Post-flood visual ratings and stand …

Optimizing A Luciferase-Based Tool For Studying The Effects Of Fatty Acid Desaturase 7 On Singlet Oxygen Accumulation In Arabidopsis Thaliana, Abeer Muhammedali Alnasrawi

Graduate Theses and Dissertations

In plants, reactive oxygen species (ROS) are generated as a byproduct of normal metabolism, as well as in response to adverse conditions such as light stress, extreme temperatures, and exposure to pests and pathogens. Singlet oxygen (1O2) is a ROS that is formed during photosynthesis in photosystem II (PSII) of the chloroplasts. Levels of 1O2 and other ROS are tightly controlled in healthy plants, but some studies suggest that levels of fatty acid desaturase (FAD) activity in Arabidopsis thaliana can influence constitutive and/or stress-responsive ROS accumulation. In this study, a luciferase-based reporter gene that is selectively stimulated by 1O2 (AAA-ATPase: …

The Effects Of Foliar Nutrient Applications On Split, Yield, And Internal Fruit Quality Of 'Wonderful' Pomegranate (Punica Granatum L.), John Matthew Chater

Master's Theses

Fruit split is the most important physiological disorder in pomegranate production, causing devastating crop losses worldwide. Foliar nutrient applications have been used experimentally to mitigate pomegranate fruit split but none have been conducted using the industry standard cultivar, Wonderful, and little is known about the effects of foliar nutrient applications on pomegranate. Additionally, investigations into putative health benefits of pomegranate fruit have increased interest in its production but limited evidence exists regarding effects of agricultural practices such as foliar fertilizer applications on internal fruit quality. ‘Wonderful’ pomegranate trees at 2 commercial orchards were treated with foliar applications of ZnSO_{4 …}

Production And Harvest Of Microalgae In Wastewater Raceways With Resource Recycling, Alexander Colin Roberts

Master's Theses

Microalgae can be grown on municipal wastewater media to both treat the wastewater and produce feedstock for algae biofuel production. However the reliability of treatment must be demonstrated, as well as high areal algae productivity on recycled wastewater media and efficient sedimentation harvesting. This processes was studied at pilot scale in the present research.

A pilot facility was operated with nine CO₂-supplemented raceway ponds, each with a 33-m² surface area and a 0.3-m depth, continuously from March 6, 2013 through September 24, 2014. The ponds were operated as three sets of triplicates with two sets continuously fed …

Demography And Disease Of The Rare Shrub Buckleya Distichophylla (Santalaceae) In Northeastern Tennessee, William Seth Ratliff

Undergraduate Honors Theses

Piratebush (Buckleya distichophylla (Nutt.) Torr.) is a rare, hemiparasitic shrub with the only extant populations in western North Carolina, northeastern Tennessee, and southwestern Virginia. The preferred natural hosts of piratebush, Carolina and eastern hemlocks, have seen sharp declines over the last decade due to the invasive hemlock woolly adelgid. Virginia pine, another important host of piratebush, is also susceptible to disease, specifically Cronartium appalachianum, a rust fungus for which piratebush is the secondary host. This study described and analyzed current demographic parameters of three Tennessee piratebush populations. Additionally, spatial patterns of disease and demographic characters were analyzed. These …

Plant Community Responses To Invasive Shrub And Vine Removal In An Urban Park Woodland., Eric Richard Moore

Electronic Theses and Dissertations

Counter to what some people think, urban areas can be biodiversity hotspots. Maintaining this biodiversity can be challenging, since exotic shrubs and vines block sunlight and threaten native plant regeneration. Since 2007, the Louisville Olmsted Parks Conservancy (LOPC) has spent $2 million on invasive plant management in Cherokee Park. Before the project began, long-term transects were established by the LOPC to collect baseline presence/absence data on 11 invasive plant species. In 2014, I revisited these transects and documented presence/absence data on the entire plant community. I found that four species (garlic mustard, winter creeper, Japanese honeysuckle, and English ivy) have …

Evaluation Of Spring Frost Control Methods And An Assessment Of Cold Hardiness In Cranberry (Vaccinium Macrocarporn Ait.), Faith Ndlovu

Doctoral Dissertations

The American cranberry (Vaccinium macrocarpon Ait.) is an important temperate woody shrub crop whose fruit has human health benefits. Cranberry acquires cold hardiness in the autumn and loses it in spring, following deacclimation. Frost protection is necessary in cranberry production as a means to reduce bud damage due to low spring temperatures. The objectives of the field studies were to evaluate two methods of sprinkler irrigation for frost protection, the conventional approach consisting of continuous irrigation throughout the night (CON) and intermittent cycling of sprinklers (INT) incorporating cycling on and off throughout the night, by (i) assessing bud damage …

Effects Of Overexpression Of Sap12 And Sap13 In Providing Tolerance To Multiple Abiotic Stresses In Plants, Parul R. Tomar

Doctoral Dissertations

Environmental stresses are the one of the main reasons for the decline of crop production worldwide. In the past years, a major focus has been on improving plant species and their tolerance towards these stresses but not much has been achieved because of the limited knowledge of the gene/network of genes that might be involved in providing tolerance to such multiple abiotic stresses. Recently, members of Stress Associated Protein (SAP) family in plants have been shown to impart tolerance to multiple abiotic stresses. There are 14 SAP genes in Arabidopsis thaliana and these proteins contain A20, AN1 and C2H2 zinc …

Inferring Plastid Metabolic Pathways Within The Nonphotosynthetic Free-Living Green Algal Genus Polytomella, Sara Asmail

Electronic Thesis and Dissertation Repository

The advent of photosynthesis facilitated the evolution of aerobic life on Earth. However, species such as Prototheca wickerhamii and Plasmodium falciparum, among many others, have lost photosynthesis and opted for a free-living/parasitic lifestyle. Despite this loss, these species have retained the plastid for its metabolic pathways, without which they would die. Polytomella is a nonphotosynthetic free-living alga, closely related to the photosynthetic model organism Chlamydomonas reinhardtii, and has been shown to lack a plastid genome. I set out to determine Polytomella plastid metabolic pathways using bioinformatics to look for mRNA and DNA homologous sequences matching pathway enzymes in model organisms. …

Planting The Chalcone Reductase Family Tree: Identification And Characterization Of Chalcone Reductase Genes In Soybean, Caroline Julia Sepiol

Electronic Thesis and Dissertation Repository

Soybean (Glycine max [L.] Merr) is an important crop grown in Canada, generating $2.4 billion in sales. Though this number may be promising, soybean farmers lose about $50 million worth of yield annually due to root and stem rot disease caused by Phytophthora sojae. Many strategies have been developed to combat the infection; however, these methods are prohibitively expensive. A ‘cost effective’ approach to this problem is to select a trait naturally found in soybean that can increase resistance. One such trait is the increased production of root glyceollins. One of the key enzymes exclusively involved in glyceollin …

Genetic Analysis Of A Non-Germinating Mutant Of Arabidopsis Thaliana, Md Jakir Hossan

Electronic Thesis and Dissertation Repository

Seed germination is partially controlled by plant hormone gibberellins (GAs). Chemical mutagenesis yielded an Arabidopsis thaliana mutant gm11, which has an absolute gibberellin requirement for seed germination. This mutant exhibited phenotypes of GA-rescuable dwarfs, including dark-green leaves, and reduced fertility. However, with repeated GA treatment, gm11 develops into fertile plants with a nearly wild type phenotype. Bulked-segregant analysis mapped gm11 to the bottom arm of chromosome 1, and subsequent next-generation mapping revealed that the mutation is a G → A transition in At1g79460 (GA2), creating a premature stop codon. This gene encodes an ent-kaurene synthase (KS) which catalyzes …

Calmodulin-Like Protein 38: A Component Of Ribonucleoprotein Particles During Hypoxic Stress Responses In Arabidopsis, Ansul Lokdarshi

Doctoral Dissertations

Waterlogging stress leads to a crisis in energy metabolism and the accumulation of toxic metabolites due to the hypoxic and/or anoxic environment associated with this condition. To respond and adapt to this situation, higher plants employ an integrated genetic program that leads to the induction of anaerobic response polypeptide genes that encode metabolic and signaling proteins involved in altering metabolic flow and other adaptive responses. The study presented here shows that the Arabidopsis thaliana calmodulin-like protein CML38 is calcium sensor protein that serves as a member of the core anaerobic response gene family and is involved in modulating the survival …

Transport Regimes And Spread Of The Common Reed, Phramites Australis, In The Saco River, Me, Usa, Michelle A. Slater

All Theses And Dissertations

Allee effects are important to species invasions because population growth may be limited by low outcrossing potential in newly founded populations leading to depressed levels of fitness. Non-native Phragmites australis (common reed) has been present in the United States for over 200 years, but has been slow to reach some areas, possibly owing to the Allee phenomenon, whereby young or isolated Phragmites patches with initially low genotypic richness are slow to recruit viable seedlings due to inbreeding, which limits the rate of patch expansion. In order to explore the importance of the Allee effect in a recently invaded system, the …

Ginsenosides, Glycosidases And The Ginseng-Pythium Interaction, Dimitre A. Ivanov

Electronic Thesis and Dissertation Repository

Ginsenosides, the triterpenoid saponins produced by American ginseng (Panax quinquefolius L.), have been extensively studied for their medicinal value, however, their function in the rhizosphere remains largely unknown. Like other saponins, ginsenosides possess mild fungitoxic activity toward some common ginseng pathogens. However, numerous oomycete root pathogens of ginseng, most notably Pythium irregulare Buisman, are able to partially deglycosylate the 20 (S)-protopanaxadiol ginsenosides Rb1, Rd and gypenoside XVII via extracellular glycosidases (ginsenosidases), leading to the formation of a common product, ginsenoside F2. In this thesis the potential role(s) of these extracellular ginsenosidases and the ginsenoside products they produce (ie. ginsenoside …

Rnai Mediated Silencing Of Cell Wall Invertase Inhibitors To Increase Sucrose Allocation To Sink Tissues In Transgenic Camelina Sativa Engineered With A Carbon Concentrating Mechanism, Joshua Zuber

Masters Theses

Plant invertases are a class of proteins that have enzymatic function in cleaving sucrose to fructose and glucose. Cell wall invertase, located on the exterior of the cell wall of plant cells, plays a key role in the unloading of sucrose from the apoplast to the sink tissues. Cell wall invertase interacts with an inhibitor, cell wall invertase inhibitor, post-transcriptionally to regulate its activity. The inhibitor is constitutively expressed in pollen development, early developing seeds, and senescing leaves: indicative of sucrose allocation being a limiting factor at these stages of development. We introduced algal bicarbonate transporters LCIA/CCP1 to Camelina sativa …

Pythium: Characterization Of Resistance In Soybean And Population Diversity, Keiddy Esperanza Urrea Romero

Graduate Theses and Dissertations

Pythium spp. are an important group of pathogens causing stand losses in Arkansas soybean production. New inoculation methods and advances in molecular techniques allow a better understanding of cultivar resistance and responses of Pythium communities to cultural practices. The objectives of this research were to i) characterize the resistance of soybean to P. aphanidermatum with two phenotyping assays that evaluated the seed rot phase of the disease; and ii) understand the effect of long term crop rotation on species diversity and iii) to determine the effect of location, temperature and continuous soybean and soybean-rice rotation on Pythium spp. diversity in …

Investigations Of Ethylene And Ethylene Inhibition, Ball Lie, And Synthetic Turf Color, William Daniel Strunk

Graduate Theses and Dissertations

This dissertation is comprised of several studies over three unrelated areas of focus. Chapters two and three investigate the role of the hormone ethylene on growth of creeping bentgrass through (1) exposure of turf to exogenous ethylene and (2) testing an ethylene inhibiting compound for use to alleviate stress related injury. Previous research demonstrated a correlation of stress injury and ethylene and lessening of injury through ethylene inhibition, but little work has been conducted evaluating the direct effects of ethylene. These studies failed to confirm findings in previous research. Chapters four and five aim to illustrate the impact of turfgrass …

Temperature In The Cotton (Gossypium Hirsutum L.) Canopy And Effects On Cotton Leaf And Boll Growth, Maria Soledad Berlangieri Costa

Graduate Theses and Dissertations

Cotton development and yield are negatively influenced by extremes temperatures, mainly during reproductive stage. Ambient air temperature is used to evaluate temperature stress effect on yield under field conditions; however, there is evidence that actual temperatures in the canopy where bolls develop are different. In terms of cotton responses, there is limited research about the effects of elevated day and night temperatures upon boll carbohydrate content, size, and boll respiration. Field and growth chamber experiments were performed during 2014-2015 using the cotton (Gossypium hirsutum L.) cultivar DP0912B2RF. Field studies for determining temperature gradients through the canopy consisted of two planting …

The Impact Of Herbicide-Resistant Rice And Hybrid Rice Technology On Weedy Rice Evolution, Vijay Singh

Graduate Theses and Dissertations

Weedy rice (Oryza sativa L.) competes aggressively with rice, reducing yields and grain quality. ClearfieldTM rice, is nontransgenic herbicide-resistant (HR) rice introduced in 2002 to control weedy rice, has resulted in ALS-resistant weedy rice due to gene flow. Volunteers of ClearfieldTM rice (F2) accelerate the HR weedy rice evolution by acting as agents of gene flow. Weedy rice (89) collected from 11 counties in Arkansas were screened for resistance in a field experiment in Stuttgart (2011). Seventy-nine percent of accessions were resistant to imazethapyr and harbored S653N mutation. These HR weedy accessions were outcrosses of ClearfieldTM rice and weedy rice. …

Alliaria Petiolata (M.Bieb.) Cavara & Grande [Brassicaceae], An Invasive Herb In The Southern Ozark Plateaus: A Comparison Of Species Composition And Richness, Soil Properties, And Earthworm Composition And Biomass In Invaded Versus Non-Invaded Sites, Jennifer D. Ogle

Graduate Theses and Dissertations

Invasive species are widely recognized as organisms that severely alter ecosystem processes in the habitats to which they are introduced. Alliaria petiolata is one of the most important invasive plants in forests of the northern United States. This study examined the geographic distribution of the plant in the southern Ozarks, as well as the effect that it may be having on natural processes within forests of the region by comparing plant species richness, plant cover, and soil properties in invaded and non-invaded plots. It was found that A. petiolata is not significantly altering species richness, cover, or soil properties in …

Identification Of Putative Plant Defense Genes Using A Novel Hydroponic Co-Cultivation Technique For Studying Plant-Pathogen Interaction, Naeem Nathoo

Electronic Thesis and Dissertation Repository

Previous work on identifying the molecular mechanisms mediating plant-pathogen interactions and reciprocal host responses have little emphasis on developing models that closely resemble host-microbe interaction in planta. This work establishes an amalgamated model of interaction wherein successful pathogens elicit and overcome host defenses activated by microbial signatures and virulence factors. Using a hydroponic co-cultivation model, we assessed the responses of Arabidopsis thaliana Col-0 to Agrobacterium tumefaciens C58 to ameliorate limitations of previous approaches. Comparisons of differential gene expression between directly and indirectly affected host sites by microarray analysis revealed both reactive and pro-active defense responses, respectively. Selected homozygous single-gene …

Descriptive Analyses Of Pollen Surface Morphologies In The Model Systems Brassica Rapa And Arabidopsis Thaliana And Three Arabidopsis Pollen Wall Mutants By Scanning Electron Microscopy, Andrew B. Kirkpatrick

Theses and Dissertations

The mechanisms behind the construction of the pollen wall are equally elaborate and mysterious. Previous studies primarily used sectioned tissue to elucidate the events involved in proper pollen development. This study proposed and evaluated a protocol for exposing developing microspores to be examined by Scanning Electron Microscopy (SEM). Utilizing this protocol, comparative analyses of the superficial features present at the early, middle, and late tetrad as well as at released microspore stages of the model plants Brassica rapa and Arabidopsis thaliana were conducted. The utility of the technique was then evaluated through the examination of three Arabidopsis pollen wall mutants …

Rice Grain Yield And Nitrogen Uptake And Ammonia Volatilization From Urea As Affected By Urea Amendment And Simulated Rainfall, Randy Dempsey

Graduate Theses and Dissertations

The effect of rainfall between urea application and flood establishment on N loss and grain yield of rice (Oryza sativa L.) has not been studied. The first research objective was to compare the effects of simulated rainfall amounts and N-(n-butyl) thiophosphoric triamide (NBPT) urease inhibitor rate on NH3 volatilization and rice growth. Three field experiments were conducted and NH3 volatilization was measured in two experiments for 11 days after urea application (DAU) in semi-open chambers. Urea or NBPT-treated urea (NBPT-Urea) was subjected to six simulated rainfall amounts (0-25 mm) applied 5 to 15 h after urea application and flooded 7 …

A Microhabitat Assessment Of Five Species Of Invasive Plants In The Ozarks And Appalachians, Eric Hearth

Graduate Theses and Dissertations

Invasive species present a threat to native communities and their introduction and expansion can alter community structure and dynamics. Multiple approaches can be employed for invasive species management including prevention and detection. In this study, microhabitat assessments were conducted on colonies of five species of invasive plants, Alliaria petiolata (M. Bieb.) Cavara & Grande, Lespedeza cuneata (Dum. Cours.) G. Don, Lonicera japonica Thunb., Microstegium vimineum (Trin.) A. Camus, and Rosa multiflora Thunb. in the Ozark Plateau and Appalachians. Elevation, soil moisture, soil pH, light ratio, slope, aspect, distance to disturbance, as well as soil nutrient levels were recorded for each …

Phylogenetic Relationships Of Samydaceae And Taxonomic Revision Of The Species Of Casearia In South-Central Asia, Tharangamala Samarakoon

Dissertations

The flowering plant family Samydaceae was recently reinstated to include 14 genera and about 256 species of tropical trees and shrubs. Preliminary analyses of relationships in the family, however, indicated that the largest genus in the family, Casearia, is not monophyletic and that several smaller groups are probably misplaced. In order to affirm or refute those hypotheses, additional DNA sequence data with broader taxon sampling from the Old World were gathered for phylogenetic analysis. In particular, rapidly evolving plastid (matK, ndhF, psbA-trnH, trnL, and trnL-F) and nuclear (EMB2765 and GBSSI) DNA …