Life Sciences Commons^™

The Evolution And Development Of Awns In The Grass Subfamily Pooideae, Erin L. Patterson

Doctoral Dissertations

This research focuses on a specific example of replicated evolution: the grass awn. Awns are typically extensions of the lemma, but may also appear on glumes or paleas. The lemma is a leaf-like organ on the exterior of the grass flower, the glumes are a pair of bracts subtending the basic unit of grass inflorescences, the spikelet, and the palea is the floral organ opposite the lemma. Awns are often described as "hair-" or "bristle-" like, but appear in many different shapes. Many awns are “twisted & geniculate", in which the awn has two sections, a lower twisted column, and …

Assessing Warm-Season Annual Grasses To Increase Forage Inventory, Andrea Marroquin

Masters Theses

Summers are expected to continue to increase in heat/dryness in the Northeast, causing issues pertaining to forage production during the summer to worsen. Many pastures grow cool season grasses, even during the summer. These grasses enter a dormant period and slowdown in production during the months of July and August, leading to what is referred to as “summer slump”. Some farms grow corn silage during the summer, and while corn silage is a valuable crop, its cultivation often does not support soil biology. This research addresses solutions for both summer slump foraging and more sustainable silage. Summer annuals grow more …

Root Growth Dynamics In Response To Moderate Temperatures, Maura J. Zimmermann

Doctoral Dissertations

Temperature can impact growth in plants though both physical and biological means. Plants physically respond to temperature by scaling their enzyme reaction rate to temperature, such as seen in the redox reactions of photosynthesis. Biologically, a plant can respond to temperature more specifically, such as adjusting its flowering time. Recently, the Baskin lab discovered that cell division in the root of the model plant Arabidopsis thaliana is temperature acclimated (Yang et al., 2017). Between the non-extreme temperatures of 15 and 25˚C cell division and growth zone length are constant. While the rate of cell division increases with temperature, the number …

Investigation Of Basil Downy Mildew Pathogen Survival, New Pathotype Development And Sources Of Quantitative, Kelly S. Allen

Doctoral Dissertations

Basil downy mildew (BDM) caused by the oomycete pathogen Peronospora belbahrii, threatens sweet basil (Ocimum basilicum) production worldwide. Chemical and cultural control options for BDM are limited, and resistant cultivars have only recently become available for commercial production. To address this challenging agricultural disease, this research investigates BDM epidemiology, occurrences of new pathotypes, and molecular plant-pathogen interactions leading to host resistance or susceptibility. A reproducible low-resource inoculation protocol was developed to harvest P. belbahrii inoculum and propagate BDM for further research. The survival of P. belbahrii sporangia was examined using an in vitro assay to assess germination …

Diterpene Synthases Of The Rice Blast Fungus: Phylogenetic Analysis And Biochemical Characterization, Ayousha Shahi

Masters Theses

Plant-pathogenic fungi harbor various specialized metabolites including diterpenoids that function as hormones and virulence factors. The fungus Magnaporthe oryzae is the causal agent of rice blast disease and can infect over 50 grass species. We demonstrate that the rice blast fungus encodes two diterpene synthases that produce normal pimara-8,15-diene and manoyl oxide scaffolds. Phylogenetic analysis of diterpene synthases among rice blast pathotypes showed functional conservation of the two core diterpene synthases amongst all pathotypes and suggests further expansion in select grass species. These insights into the blast fungal terpenome may inform efforts to counteract deleterious phytopathogens in crucial food crops.

Screening For Binding Partners And Protein-Protein Interactions Of A Fungal Transcription Factor- Xdr1, Nishadi Punsara Gallala Gamage

Masters Theses

Clarireedia spp. (formerly Sclerotinia homoeocarpaF.T. Bennett) is the causal agent dollar spot, the most economically important turfgrass disease impacting golf courses in North America. The most effective strategy for dollar spot control is repeated application of multiple classes of fungicides. However, reliance on chemical application has led to resistance to four classes of fungicides as well as multidrug resistance (MDR). Fungi are known to detoxify xenobiotics, like fungicides, through transcriptional regulation of three detoxification phases: modification, conjugation and secretion. Little is known, however, of the protein-protein interactions that facilitate these pathways. Following next-generation RNA sequencing of Clarireedia spp., a …

Genetic And Environmental Regulation Of Plant Growth, Kirk J-M Mackinnon

Doctoral Dissertations

Field grown crops are continually exposed to a variety of external stimuli that influence plant responses. Light, temperature, and water availability interact to affect many economically important traits including growth rate, size, and lifespan. My research is focused on the intersection of genetic and environmental factors influencing plant growth. Specifically, I am interested in elucidating the regulation of rhythmic genes in response to photo- and thermocycles and identifying novel candidate genes associated with growth and drought traits. Understanding the gene regulatory networks that mediate time-of-day signaling is vital to identifying candidate genes across the pan-genome associated with traits of interest.

Plants, Pipettes And Pcr, Elizabeth Vierling

Science and Engineering Saturday Seminars

Plants are amazing organisms that provide us with food, building materials, the pleasure of gardens, as well as providing the foundation of critical world ecosystems. Although they may look like they are just stuck in one place and doing not more than growing, they have many, many complex ways in which they respond to the environment. The goal of this STEM Ed session will be to discuss ways that plants can respond to the environment with hands on exercises and exploration of possible classroom activities. Participants will engage in state-of-the art methods of testing plant DNA composition using the polymerase …

The Characterization Of Traits Associated With Freezing Tolerance In Perennial Ryegrass, Rachael Preston Bernstein

Doctoral Dissertations

Plants are constantly subjected to adverse environmental conditions that alter their growth and productivity, with an estimation that approximately 50% of annual average crop yields are reduced due to abiotic stresses. Freezing stress causes desiccation and ice damage in plants and is becoming more important as temperatures and unpredictable weather patterns increase. Normally, plants acclimate to cold temperatures as winter approaches and deacclimate as temperatures warm in the spring. Cold acclimation in fall is required for plants to build up their cellular defenses against desiccation and intracellular ice formation, while deacclimation is the process in which plants metabolize protective compounds …

Trait Variation And Long-Term Population Dynamics Of The Invasive Alliaria Petiolata (Garlic Mustard) Across Three Microhabitats In Its Invaded Range, Laura Hancock

Masters Theses

Long-term population dynamics across heterogeneous environments can be a major factor in determining species’ ability to expand their ranges and persist in novel environments. Whether and how the relative performance of populations in different microsites over time impacts invasion into new microsites is poorly understood. Though largely restricted to disturbed semi-shaded microhabitats in its home range, the invasive herb Alliaria petiolata (garlic mustard) successfully invades intact forest understories – a novel microhabitat – in its introduced range, where it is known to impact above and below ground community composition. To test the hypothesis that source-sink metapopulation dynamics may be promoting …

Assessing Stress Tolerance Of Organelle Small Heat Shock Protein Mutants In Arabidopsis Thaliana, Parth Patel

Masters Theses

Molecular chaperones are proteins found in virtually every organism and are essential to cell survival. When plants are heat stressed, they upregulate and downregulate multiple genes, many of which are associated with the heat shock response. Small heat shock proteins (sHSPs) are one class of molecular chaperones that are upregulated during heat shock. They are proposed to act as the first line of defense by binding to heat sensitive proteins and preventing their irreversible aggregation. However, many details of sHSP function remain to be discovered and exactly what proteins they protect is unresolved. In addition to cytosolic sHSPs found in …

Origin Of Gene Specificity In The Nitrogen-Fixing Symbiosis, Christina Marie Stonoha-Arther

Doctoral Dissertations

Many legumes form a symbiosis with nitrogen-fixing bacteria found in the soil. This relationship is beneficial to both the plant and the bacteria; the plant receives nitrogen that is otherwise limited, and the bacteria receive fixed carbon. Upon sensing the bacteria, the plant forms a new organ (the nodule) where the bacteria are housed within the cells. Many genes are required for the proper formation and function of nodules; this dissertation is broadly focused on how genes required for nitrogen-fixing symbiosis are co-opted from other cellular processes and how they are specialized for symbiosis. Protein trafficking from the plant to …

Investigating The Transcriptional Regulation Of Secondary Cell Wall Synthesis And Thigmomorphogenesis In The Model Grass Brachypodium Distachyon, Joshua Coomey

Doctoral Dissertations

A key aspect of plant growth is the synthesis and deposition of cell walls. In specific tissues and cell types including xylem and fiber, a thick secondary wall composed of cellulose, hemicellulose, and lignin is deposited. Secondary cell walls provide a physical barrier that protects plants from pathogens, promotes tolerance to abiotic stresses, and fortifies cells to withstand the forces associated with water transport and the physical weight of plant structures. Grasses have numerous cell wall features that are distinct from eudicots and other plants. Study of the model species Brachypodium distachyon has helped us begin to understand the internal …

Brachypodium Distachyon Gnrf, Swam1 And Swam4 Are Transcriptional Regulators Of Secondary Cell Wall Biosynthesis, Sandra Romero-Gamboa

Doctoral Dissertations

Plant cell walls are complex structures that contain a matrix of cellulose, lignin and hemicellulose. The regulation of the biosynthesis of these components has been well-studied in the eudicot plant Arabidopsis thaliana, and a transcriptional network has been elucidated. Several NAC and MYB family transcription factors are key regulators of secondary cell wall biosynthesis, and their functional characterization provides significant insight into the complex underlying transcriptional network. Genetic and structural evidence suggests that genes controlling this process might be different between eudicots and monocots. Here, the model grass Brachypodium distachyon has been selected to characterize the function of GNRF …

The Good, The Bad, And The Ugly: Pollinators As Vectors Of Mummy Berry Disease In Highbush Blueberry, Matthew Boyer

Doctoral Dissertations

Background: Many plants must balance the need for pollination services with mediating the risk of pollinator-vectored pathogens. Vaccinium corymbosum, highbush blueberry, is negatively affected by an insect-vectored, fungal plant pathogen, Monilinia vaccinii-corymosi (MVC), the cause of mummy berry disease, in which the asexual spore mimics pollen grains and is transferred from blighted tissue to flowers via pollinators, resulting in inedible, hardened fruits. Highbush blueberry plants require outcrossed pollen for maximum yield and fecundity. Therefore, yield of blueberry plants rely on a balance between adequate pollination service and disease avoidance. Approach: To explore the relationship between pollinator community and infection …

Variation And Evolution Of Fruit Ripening Traits In Tomato Species, Ian M. Gillis

Doctoral Dissertations

As angiosperm seeds mature within their ovaries, ovary tissue tends to grow and transform itself into fruit, which aids the success of the seeds. Fruits that are fleshy provide numerous ways to aid in the protection and the dispersal of seeds. First, they keep seeds hidden, encased in hard walls, surrounded by poisons and unpalatable compounds, and second, they undergo developmental changes that facilitate seeds’ release. Tomatoes, a model fleshy fruit, have all these protective traits, and over the course of ripening they become the familiar fruit that is a staple crop around the world. The wild relatives of cultivated …

Grass-Specific Mechanisms Of Iron Uptake: Investigation Of Phytosiderophore Transporters And Discovery Of Novel Iron Deficiency Loci, David Chan Rodriguez

Doctoral Dissertations

Iron-deficiency anemia is one of the most prevalent forms of malnutrition worldwide, affecting 1.62 billion people, with the population in developing countries being the most affected. Iron is equally vital in plants to perform essential functions such as photosynthesis. Crop grasses form part of everyday human nutrition, contribute fundamentally to human caloric intake, and, in some parts of the world, are the primary source of food. Grasses acquire iron from the soil by secreting chelator molecules called phytosiderophores to solubilize iron, making it available to be transported by the Yellow Stripe1 (YS1) transporter. In this dissertation, I studied aspects of …

The Interplay Between Polarity Regulators, Calcium, And The Actin Cytoskeleton During Tip Growth, Carlisle Bascom Jr

Doctoral Dissertations

Plant cell growth is a meticulously regulated process whereby the cell wall is selectively loosened to allow for turgor-pressure driven expansion. The rate of expansion must equal delivery of new material, or the cell will lyse. In many plant cells, this process happens diffusely around the cell. However, a number of plant cells have anisotropic shapes that require exquisite spatial control of secretion. One simple example of anisotropic patterning is tip growth; highly polarized cell expansion utilized by pollen tubes, root hairs, and moss protonemata. Investigating the role various molecules have in tip growth sheds light on how plant cells …

Uncovering Tasselsheath3. A Genomic And Phenotypic Analysis Of A Maize Floral Mutant., Thompson Zhang

Masters Theses

In the modern era, maize has become the most successful crop grown in the United States. According to the USDA over 90 million acres of land are planted to corn and 96.2% of the U.S feed grain production is made up of the cereal. Part of the success of maize is due to its floral architecture, and its pollination technique in which the flower opens, exposing stamens containing pollen into the air. A unique organ called the lodicule functions as a release mechanism, forcing the flower to open. Lodicules from grasses and eudicot petals are homologous, yet there is little …

The Key Question In Symbiotic Nitrogen Fixation: How Does Host Maintain A Bacterial Symbiont?, Onur Oztas

Doctoral Dissertations

The fact that plants cannot use nitrogen in the gaseous form makes them dependent on the levels of usable nitrogen forms in the soil. Legumes overcome nitrogen limitation by entering a symbiotic association with rhizobia, soil bacteria that convert atmospheric nitrogen into usable ammonia. In root nodules, bacteria are internalized by host plant cells inside an intracellular compartment called the symbiosome where they morphologically differentiate into nitrogen-fixing forms by symbiosome-secreted host proteins. In this project, I explained the host proteins required to maintain bacterial symbionts and described their delivery to the symbiosome. I showed that the SYNTAXIN 132 (SYP132) gene …

Comparative Transcriptome Analysis Of Wild Tomato Species During Fruit Development, Altynay Zhanayeva

Masters Theses

Fleshy fruits in different species can display large variation in color. A link between fruit color and seed dispersal success is suggested by previous studies showing that high intensity of fruit color increases the visitation rate in seed-dispersing birds. Wild tomato species (Solanum spp.) are excellent model organisms for research on genetic basis of differential fruit color development during the ripening process. Despite polymorphism in fruit color, all tomato species have yellow flowers due to accumulation of carotenoid pigments, which suggests that the carotenoid pathway is intact. Thus, regulatory changes controlling enzymes activity during fruit maturation are likely …

Iron Signaling In Arabidopsis Thaliana, Celina Abundis

Masters Theses

Iron is among the essential micronutrients for all living organisms and is a cofactor for many cellular redox reactions. Although iron is a highly abundant metal element found in the earth’s crust, it is also a limiting factor in plant development when it is present as insoluble ferric oxides. Plants have evolved two strategies to acquire soluble iron referred to as Strategy I and Strategy II. Our lab has focused on the Arabidopsis thaliana double mutant ysl1ysl3. The mutants display a chlorotic phenotype and are unable to correctly respond to iron deficiency.

Grafting is a common method for joining …

Chemically Mediated Interactions Between Hosts, Parasitic Plants And Insect Herbivores, Muvari C. Tjiurutue

Doctoral Dissertations

Species interactions, by changing phenotypic traits, can alter the outcome of subsequent interactions. Plant-mediated responses to herbivores have been extensively studied, but little is known about plant-mediated responses involving parasitic plants within a broader community context that also includes herbivores. Because parasitic plants are important components of many ecosystems and can shape community structure, it is important to understand how host-mediated interactions influence parasite preference and success. The goal of this thesis is to examine interactions between hosts, parasitic plants and herbivores mediated by chemical traits. We first examined the effects of dodder (Cuscuta sp.) parasitism on induced defenses …

Variations In The Invertebrate Communities Of Wild Cape Cod Cranberry Bogs, Barbara Wagner

Masters Theses

As a species domesticated only in the last century, agricultural cranberry plants (Vaccinium macrocarpon) remain little removed from their wild relatives. Thus, it is a potential model species for studies of the earliest stages of domestication; however, there is little available quantitative information on its wild population biology and ecology. As such information is vital to studies of the ecological changes occurring during domestication, the purpose of this study was to consolidate the relevant knowledge available and conduct a preliminary search for patterns in the invertebrate communities of wild bogs. The alpha diversity was found to be greater …

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 …

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 …

Thermocycle-Regulated Wall Regulator Interacting Bhlh Encodes A Protein That Interacts With Secondary-Cell-Wall-Associated Transcription Factors, Ian P. Whitney

Masters Theses

Lignocellulosic biomass is one of the most abundant raw materials on earth that can be utilized to created carbon-neutral biofuels as a replacement for conventional fossil fuels. In order to create ideal energy crops, the regulation and deposition of cell wall polysaccharides must first be fully understood. Improved understanding of cell wall regulation will enable selection of traits that can optimize biofuel feedstocks. Herein, I utilize the grass model system Brachypodium distachyon in order to understand the transcriptional regulation of secondary cell wall deposition. Gene expression profiling was used to elucidate transcription factors that regulate secondary cell wall biosynthesis. Through …

Understanding The Transcriptional Regulation Of Secondary Cell Wall Biosynthesis In The Model Grass Brachypodium Distachyon, Pubudu Handakumbura

Doctoral Dissertations

Secondary cell wall synthesis occurs in specialized cell types following completion of cell enlargement. By virtue of mechanical strength provided by a wall thickened with cellulose, hemicelluloses, and lignin, these cells can function as water-conducting vessels and provide structural support. Several transcription factor families regulate genes encoding wall synthesis enzymes. Certain NAC and MYB proteins directly bind upstream of structural genes and other transcription factors. The most detailed model of this regulatory network is established predominantly for a eudicot, Arabidopsis thaliana. In grasses, both the patterning and the composition of secondary cell walls are distinct from that of eudicots. …

Volatile Profiles And Resistance To Herbivory In Eastern Hemlock, Elizabeth A. Mckenzie

Masters Theses

Eastern hemlock hosts the hemlock woolly adelgid, an introduced sap-feeding insect that causes rapid deterioration of the host. Like most conifers, eastern hemlock produces a variety of constitutive and induced defenses, primarily terpenoids. To explore the relationship of terpenoid defenses with adelgid infestations, we artificially infested hemlocks at a forest site and a plantation site, and compared their terpenoid concentrations to those in control trees. Infested trees showed lower terpenoid concentrations than control trees, suggesting that eastern hemlock not only fails to induce production of terpenoids in response to adelgid infestation, but becomes less able to produce carbon-based defenses due …