Agriculture Commons^™

Virus-Induced Changes In Nuclear Proteins And Membranes In Nicotiana Benthamiana Cells, Caleb Mathias

Theses and Dissertations--Plant Pathology

Viruses rely on host proteins to complete their life cycles. This results in alterations to normal cell physiology to processes which benefit viral processes such as replication and movement to other cells. This may involve the relocalization of host proteins away from their original subcellular targets to sites which may benefit the virus, a process that is not as well understood as it relates to the nucleus. To identify nuclear proteins that may be involved in such processes, a library of random Nicotiana benthamiana cDNAs were expressed as GFP fusions in a transgenic marker lines expressing a histone 2B:RFP nuclear …

Extracting Secondary Metabolites From Bacterial Endophytes To Suppress Or Promote Sweet Sorghum And Weeds, Mohammad R. Alsabri

Theses and Dissertations--Plant and Soil Sciences

Endophytic bacteria are ubiquitous in agricultural settings and have the potential to drastically affect plant growth both positively and negatively. These complex relationships play a key role in plant nutrition and are therefore of great interest to the agricultural community and beyond. With my dissertation work, I have had the opportunity to examine the relationship between endophytic bacteria and plants in various ways. The first part of my dissertation investigated how the microbial diversity found in soil affects the below- and above-ground traits of Sorghum bicolor. In the second section, I focused on a particular strain of bacteria that …

Host Restriction Factors In The Replication Of Tombusviruses: From Rna Helicases To Nucleocytoplasmic Shuttling, Cheng-Yu Wu

Theses and Dissertations--Plant Pathology

Positive-stranded (+)RNA viruses replicate inside cells and depend on many cellular factors to complete their infection cycle. In the meanwhile, (+)RNA viruses face the host innate immunity, such as cell-intrinsic restriction factors that could block virus replication.

Firstly, I have established that the plant DDX17-like RH30 DEAD-box helicase conducts strong inhibitory function on tombusvirus replication when expressed in plants and yeast surrogate host. This study demonstrates that RH30 blocks the assembly of viral replicase complex, the activation of RNA-dependent RNA polymerase function of p92pol and viral RNA template recruitment.

In addition, the features rendering the abundant plant DEAD-box helicases either …

Bacterial Inoculants, Endophytic Bacteria And Their Influence On Nicotiana Physiology, Development And Microbiome, Andrea Marisa Sanchez Barrios

Theses and Dissertations--Plant and Soil Sciences

Soil and root microbial communities have been studied for decades, and the incorporation of high-throughput techniques and analysis has allowed the identification of endophytic/non-culturable organisms. This has helped characterize and establish the core microbiome of many model plant species which include underground and aboveground organs. Unfortunately, the information obtained from some of these model plants is not always transferable to other agronomic species. In this project, we decided to study the microbiome of the Nicotiana genus because of its importance in plant physiological and plant-microbe interactions studies. The data obtained was used as baseline information that allowed us to better …

Identifying Mechanisms Of Host Plant Specialization In Aphis Craccivora And Its Bacterial Symbionts, Thorsten Hansen

Theses and Dissertations--Entomology

Many insects form close relationships with microbial symbionts. Insect symbionts can provide novel phenotypes to their hosts, including influencing dietary breadth. In the polyphagous cowpea aphid, Aphis craccivora, the facultative symbiont Arsenophonus improves aphid performance on one host plant (locust), but decreases performance on other plants. The goal of my thesis was to investigate the mechanism by which Arsenophonus facilitates use of locust. First, I assembled an Aphis craccivora-Arsenophonus-Buchnera reference transcriptome to conduct RNAseq analysis, comparing gene expression in aphids feeding on locust and fava, with and without Arsenophonus infection. Overall, few transcripts were differentially …

Understanding The Molecular Mechanisms Underlying Rsv1 Mediated Resistance To Smv In Soybean, Mohammed Ali Ahmed Eid

Theses and Dissertations--Plant Pathology

Like humans, viral diseases also affect plants. Of these, viruses belonging to the potyvirus genus are the most prolific. The potyvirus soybean mosaic virus (SMV) is an important pathogen of the crop plant soybean. SMV causes mosaic symptoms (yellow areas alternate with dark green areas on the leaves of the plant) and can affect yield by reducing seed quality. Few cultivars from soybean can resist different SMV strains. To understand soybean defense mechanisms to SMV, I identified soybean proteins that interact with the helper component protease (HC-Pro) of SMV, which also functions as the suppressor of host RNA silencing and …

Toxicity Of Engineered Nanomaterials To Plant Growth Promoting Rhizobacteria, Ricky W. Lewis

Theses and Dissertations--Plant and Soil Sciences

Engineered nanomaterials (ENMs) have become ubiquitous in consumer products and industrial applications, and consequently the environment. Much of the environmentally released ENMs are expected to enter terrestrial ecosystems via land application of nano-enriched biosolids to agricultural fields. Among the organisms most likely to encounter nano-enriched biosolids are the key soil bacteria known as plant growth promoting rhizobacteria (PGPR). I reviewed what is known concerning the toxicological effects of ENMs to PGPR and observed the need for high-throughput methods to evaluate lethal and sublethal toxic responses of aerobic microbes. I addressed this issue by developing high-throughput microplate assays which allowed me …

Nuclear Import And Interactions Of Potato Yellow Dwarf Virus Nucleocapsid, Matrix, And Phosphoprotein, Gavin Lloyd Franklin Anderson

Theses and Dissertations--Plant Pathology

Potato yellow dwarf virus (PYDV) is the type species of the genus Nucleorhabdovirus and, like all members of this genus, replication and morphogenesis occurs inside the nuclei of infected cells. Protein localization prediction algorithms failed to identify a nuclear localization signal (NLS) in PYDV nucleocapsid (N) protein, although PYDV-N has been shown to localize exclusively to the nucleus when expressed as a green fluorescent protein (GFP):N fusion in plant cells. Deletion analysis and alanine-scanning mutagenesis identified two amino acid motifs, ⁴¹⁹QKR⁴²¹ and ⁴³²KR⁴³³, that were shown to be essential for nuclear import and interaction with …

The Role Of Surface Chemistry In The Toxicity Of Manufactured Cerium Dioxide Nanomaterials To Caenorhabditis Elegans, Emily Kay Oostveen

Theses and Dissertations--Plant and Soil Sciences

Manufactured CeO₂ nanomaterials (CeO₂-MNMs) are used for a wide variety of applications including diesel fuel additives and chemical/mechanical planarization media. To test the effects of CeO₂-MNM surface coating charge on to model organism Caenorhabditis elegans, we synthesized 4 nm CeO₂ with cationic (DEAE-), anionic (CM-), and neutral (DEX) coatings. In L3 nematodes exposed for 24 hours, DEAE-CeO₂ induced lethality at lower concentrations than CM- or DEX-CeO₂. Feeding slightly decreased CeO₂ toxicity, regardless of coating. In L2 nematodes exposed for 48 hours with feeding, DEAE-CeO₂ caused lethality at the …

The Effects Of Slow Release Urea On Nitrogen Metabolism In Cattle, Vaughn B. Holder

Theses and Dissertations--Animal and Food Sciences

The objective of this research was to investigate the effects of slow release urea on N metabolism in cattle. The ruminal behavior of Optigen®II and the effect of basal diet on the in situ degradability of urea and Optigen®II were evaluated. The effect of slow release urea and its interaction with degradable intake protein (DIP) level in the diet on N retention and excretion was evaluated utilizing 8 Holstein steers in a 4 x 4 Latin square experiment. In addition, the effect of slow release urea and DIP level on ruminal and systemic urea kinetics was evaluated using stable isotope …

Soil Microbial Community Response To Climate Change: Results From A Temperate Kentucky Pasture, Lindsey C. Slaughter

Theses and Dissertations--Plant and Soil Sciences

Climate change is likely to alter plant species composition and interactions between plants and soil microbes that together dictate the quantity and quality of forage produced in pastures, the base of animal production in central Kentucky. This study assessed the seasonal dynamics of soil microbes and their response to increased temperature (+3^oC) and growing season precipitation (+30% of the mean annual). Total soil microbial biomass, community composition, enzyme activities, potential carbon mineralization, and catabolic responses to selected substrates were measured seasonally in the different climate treatments. In this system, seasonal variability was a dominant driving factor for all …