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- Title
- Systematics of the genus Rhagoletis (Diptera : Tephritidae : new species, phylogeny, and justifications
- Creator
- Hulbert, Daniel Lloyd
- Date
- 2018
- Collection
- Electronic Theses & Dissertations
- Description
-
Flies of Rhagoletis (Diptera: Tephritidae) are economically important fruit pests (infesting specialty fruit crops including apples, blueberries and cherries), which also serve as models for studying modes of speciation and coevolutionary relationships with their hymenopteran parasitoids. There are new species within the genus which have not been previously formally described. One of these species is within the tabellaria species group. I describe the morphology of Rhagoletis bushi Hulbert &...
Show moreFlies of Rhagoletis (Diptera: Tephritidae) are economically important fruit pests (infesting specialty fruit crops including apples, blueberries and cherries), which also serve as models for studying modes of speciation and coevolutionary relationships with their hymenopteran parasitoids. There are new species within the genus which have not been previously formally described. One of these species is within the tabellaria species group. I describe the morphology of Rhagoletis bushi Hulbert & Smith, its geographic distribution, host association, phylogenetic relationships, and identify an associated species of parasitoid wasp. The new species infests the fruit of buffaloberry (Shepherdia argentea) in the Northern Great Plains of North America. There is a suite of morphological characters, and a unique host plant association, that are diagnostic of R. bushi. Further evidence for the validity of R. bushi and its placement within the tabellaria species group comes from DNA sequence data from multiple genetic loci. The phylogenetic relationships among Rhagoletis species groups remain unresolved despite analyses based on morphology, allozymes, and mitochondrial DNA. Most Nearctic Rhagoletis belong to one of five species groups (pomonella, tabellaria, cingulata, suavis , and ribicola groups), with two unplaced species (R. fausta and R. juniperina), all of which appear to be part of a larger monophyletic group that also includes some Palearctic taxa. Regarding the overall phylogeny of the genus, my goals were to 1) resolve phylogenetic relationships using mitochondrial (COI) and nuclear (28S, CAD, period, AATS) DNA sequences, and 2) to identify the monophyletic group containing these Nearctic species. Using Bayesian analysis of a combined dataset with 4399 aligned nucleotides, I inferred a well-supported monophyletic group containing the five Nearctic Rhagoletis species groups, plus R. fausta, R. juniperina, and two Palearctic species: R. batava and R. flavigenualis. Within this larger monophyletic assemblage, the five Nearctic species groups together are monophyletic as are four of the five individual species groups (not ribicola). Palearctic and Neotropical Rhagoletis were resolved into well-supported clades of taxa often sharing closely related host plants. A well-resolved phylogeny of Rhagoletis is a valuable tool for future work addressing questions pertaining to how history, geography and ecology have shaped the phylogenetic patterns we observe in the genus. It is often claimed that systematic biology is fundamental to all other areas of biology. I critically evaluate the acceptance of this claim by entomologists critically as it relates to the field of entomology. I also critically describe the justification and valuations for systematic biology using the framework of Boltanski and Thevenot's realms of worth and the philosophical framework for justification using virtues, desserts and outcomes. In order to accomplish these purposes, I critically analyze and review relevant entomological literature and interview practitioners of entomology and insect systematic biology. I find justification for systematic biology overwhelming takes the form of appeals to utilitarianism (both internally and externally focused) and are most relevant in the Industrial World. Additionally, some justifications given also pertain to the Civic World and to virtue. Evaluation of justification in systematic biology is important, especially as our globe becomes increasingly ecologically and politically unstable.
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- Title
- Disease, pollinator, and resource limitation influences on the reproductive biology and growing season of Arisaema Triphyllum, Jack-in-the-Pulpit
- Creator
- Cook, Jessica L.
- Date
- 2004
- Collection
- Electronic Theses & Dissertations
- Title
- Host preferences and host suitability of ten hardwoods for the Asian longhorned beetle, Anoplophora glabripennis and of four conifers for the white-spotted pine sawyer, Monochamus scutellatus
- Creator
- Lazarus, Laura Lenore
- Date
- 2003
- Collection
- Electronic Theses & Dissertations
- Title
- Characterization of biochemical elements important for host-pathogen interaction in the Rhizobium-legume system : a paradigm of infection
- Creator
- Wang, Jianjun
- Date
- 1997
- Collection
- Electronic Theses & Dissertations
- Title
- Understanding the molecular basis of disease susceptibility of Arabidopsis to Pseudomonas syringae pv. tomato DC3000
- Creator
- Hauck, Paula Margaret
- Date
- 2004
- Collection
- Electronic Theses & Dissertations
- Title
- Virulence of Pseudomonas syringae pv. tomato strain DC3000 on Arabidopsis thaliana
- Creator
- Zwiesler-Vollick, Julie
- Date
- 2002
- Collection
- Electronic Theses & Dissertations
- Title
- The geographic distribution of silene latifolia and its anther-smut pathogen microbotryum violaceum in the eastern United States
- Creator
- Lyons, Emily J. (Emily Jane)
- Date
- 1996
- Collection
- Electronic Theses & Dissertations
- Title
- Investigation of the role of plant cell wall degrading enzymes in host-pathogen interactions
- Creator
- Görlach, Jenifer M. (Jenifer Marie)
- Date
- 1997
- Collection
- Electronic Theses & Dissertations
- Title
- Type III virulence effectors of pseudomonas syringae pv. tomato strain DC3000
- Creator
- Bandyopadhyay, Sruti
- Date
- 2003
- Collection
- Electronic Theses & Dissertations
- Title
- Temperature modulation of salicylic acid-mediated signaling and Pseudomonas syringae pv. tomato DC3000 pathogenesis in Arabidopsis thaliana
- Creator
- Huot, Bethany
- Date
- 2016
- Collection
- Electronic Theses & Dissertations
- Description
-
A predominant issue of global concern is increasing agricultural output to meet the steady rise in global demand. One of the most significant challenges to meeting this objective is overcoming crop loss due to disease and adverse weather. While individual biotic and abiotic stresses are damaging to plants, they can have catastrophic affects when combined, as most often occurs in the field. It has long been observed that environmental conditions, such as temperature and humidity, play a...
Show moreA predominant issue of global concern is increasing agricultural output to meet the steady rise in global demand. One of the most significant challenges to meeting this objective is overcoming crop loss due to disease and adverse weather. While individual biotic and abiotic stresses are damaging to plants, they can have catastrophic affects when combined, as most often occurs in the field. It has long been observed that environmental conditions, such as temperature and humidity, play a determining role in the outcome of plant-pathogen interactions. Both low and high temperatures have been shown to promote disease depending on the pathosystem involved. Salicylic acid (SA) is a plant hormone important for protection against a broad spectrum of crop-relevant pathogens. However, the direct effect of elevated temperature on SA-mediated defense is unknown. The aims of the research described here were to determine 1) what impact elevated temperature has on SA biosynthesis and signaling, 2) whether observed effects are a direct result of temperature on the host or are also pathogen-dependent and 3) how observed temperature effects on the plant and pathogen interact to determine the final disease outcome. Using the model Arabidopsis thaliana and Pseudomonas syringae pv. tomato DC3000 plant-pathosystem, I present evidence demonstrating that loss of SA biosynthesis and enhanced delivery of bacterial type III effector (T3E) proteins into the plant cells at elevated temperature (30°C) both contribute to enhanced disease.In the host, both SA biosynthesis and signaling are affected in a pathogen-independent manner resulting in enhanced susceptibility. Global transcriptome profiling revealed a temperature-sensitive bifurcation in the SA signaling pathway, with 66% of benzothiadiazole (BTH)-regulated genes, including ISOCHORISMATE SYNTHASE 1 (ICS1) and the widely-used SA marker genes PATHOGENESIS RELATED 1 (PR1), PR2 and PR5, showing compromised expression at 30°C. Surprisingly, BTH-mediated protection against disease is maintained at elevated temperature in spite of the loss of the temperature-sensitive PR1/ICS1 branch of SA-signaling. Exploration of a potential mechanism for SA-mediated protection revealed a novel role of SA in restricting translocation of bacterial T3E into host cells, as translocation was increased in SA-deficient mutants and reduced in BTH-treated plants at 23°C. However, there also seems to be a direct effect of temperature on the pathogen, as T3E translocation was increased more in response to elevated temperature than SA-deficiency.Taken together, these findings support a model whereby elevated temperature acts on both the host, resulting in loss of SA biosynthesis, and on the pathogen, resulting in increased secretion of T3E proteins into plant cells, to promote enhanced bacterial multiplication and disease. Provision of an SA signal, such as BTH, is sufficient to reduce translocation of effector proteins to confer protection against disease. As BTH is used commercially as a crop protectant, the discovery of preserved BTH-mediated protection at elevated temperatures is agriculturally relevant. Furthermore, exploration of the temperature-sensitive and -insensitive branches of SA signaling may also be used to inform genetic approaches to achieve plant resilience to disease under adverse environmental conditions.
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- Title
- Induced responses of poplars to defoliation and their effects on leaf-feeding lepidoptera
- Creator
- Parry, Dylan
- Date
- 2000
- Collection
- Electronic Theses & Dissertations
- Title
- Combining host plant resistance and managed fungicide applications for control of late blight in potatoes
- Creator
- Muhinyuza, Jean-Baptiste
- Date
- 2003
- Collection
- Electronic Theses & Dissertations
- Title
- Study of the virulence protein avre in Pseudomonas syringae pathogenesis
- Creator
- Uribe-Romeo, Francisco Jose
- Date
- 2011
- Collection
- Electronic Theses & Dissertations
- Description
-
AvrE is an effector protein injected into the plant cell by the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000 through the type three secretion system to promote disease. AvrE and its orthologs in other species of pathogenic bacteria, such as DspE in Erwinia amylovora and WtsE in Pantoea stewartii, are major virulence factors. Deletion of genes encoding AvrE-family effectors often greatly reduces the virulence of bacterial pathogens. Despite their importance in bacterial...
Show moreAvrE is an effector protein injected into the plant cell by the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000 through the type three secretion system to promote disease. AvrE and its orthologs in other species of pathogenic bacteria, such as DspE in Erwinia amylovora and WtsE in Pantoea stewartii, are major virulence factors. Deletion of genes encoding AvrE-family effectors often greatly reduces the virulence of bacterial pathogens. Despite their importance in bacterial pathogenesis, the virulence functions of AvrE-family effectors remain enigmatic.This dissertation describes a detailed sequence-function study of the AvrE protein, which does not share any significant overall sequence similarities with other proteins, except for other members of the AvrE family. Several sequence motifs and conserved amino acid residues were identified and shown to be important for AvrE function. Most intriguing was the finding that the N-terminal and central regions of AvrE contain two WxxxE motifs, which are also found in some mammalian pathogen effectors that function as novel guanine nucleotide exchange factors (GEFs). Site-directed mutagenesis and pathogenesis assays were performed, yielding information about the essential amino acid features required for the function of the WxxxE motif in AvrE. In the C-terminus of AvrE, another conserved motif, LKKxGxE, was found. Results from site-directed mutagenesis and pathogenesis assays suggest that a pair of lysine residues in this motif is essential for the virulence function of AvrE.Transgenic expression of AvrE was found to be toxic to plant and yeast cells, suggesting that the host targets of AvrE may be conserved among eukaryotes. A large-scale screen was performed to identify Arabidopsis proteins that were capable of suppressing AvrE toxicity in yeast, by cotransforming avrE and an Arabidopsis cDNA library into yeast cells. In addition, non-toxic, truncated AvrE derivatives were used in yeast two-hybrid screens to identify Arabidopsis proteins that could interact with AvrE. Although several candidate host proteins were isolated, further studies to determine their relevance to the AvrE function during bacterial infection gave no definitive answers. Nonetheless, an AvrE fragment spanning the first 522 amino acids interacted with the Arabidopsis protein Rad23-A, a known interactor of another Pst DC3000 effector, HopM1. Previous studies have shown that AvrE and HopM1, although dissimilar in protein sequences, are functionally redundant, presumably because they affect the same host cellular processes. Rad23-A was found to be degraded during infection of Arabidopsis plants with Pst DC3000, but degradation was not observed when plants were infected with the CEL mutant bacteria, in which both avrE and hopM1 are deleted. The CEL mutant complemented with either the avrE or hopM1 gene induced degradation of Rad23-A during infection. Rad23-A may be used as a molecular marker for the virulence function of AvrE and HopM1 in Pst DC3000 infection of Arabidopsis.
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- Title
- Characterization of the ARF guanine nucleotide exchange factor MIN7 and the RabE1 GTPases of Arabidopsis
- Creator
- Imboden-Davison, Lori A.
- Date
- 2011
- Collection
- Electronic Theses & Dissertations
- Description
-
Pseudomonas syringae pv tomato DC3000 is a Gram-negative bacterium that utilizes a type three secretion system to translocate effector proteins into plant cells to promote pathogenesis. There are ~30 effectors secreted by Pst DC3000 and the effectors HopM1 and AvrPto have both been implicated in targeting host vesicle trafficking systems. HopM1 has been shown to promote disease by targeting HopM1 interactor 7 (MIN7). MIN7 contains the SEC7...
Show morePseudomonas syringae pv tomato DC3000 is a Gram-negative bacterium that utilizes a type three secretion system to translocate effector proteins into plant cells to promote pathogenesis. There are ~30 effectors secreted by Pst DC3000 and the effectors HopM1 and AvrPto have both been implicated in targeting host vesicle trafficking systems. HopM1 has been shown to promote disease by targeting HopM1 interactor 7 (MIN7). MIN7 contains the SEC7 domain, the catalytic domain of ADP-ribosylation factor (ARF) guanine nucleotide exchange factors (GEFs). ARF GEFs promote the exchange of GTP for GDP on ARF GTPases, but GEF activity has not been demonstrated for MIN7. In this research I show that the SEC7 domain of MIN7 is capable of promoting the exchange of GTP for GDP on an Arabidopsis ARF GTPase. In addition, I found that MIN7::DsRed was partially co-localized with at least five Arabidopsis ARFs. min7 plants are compromised in salicylic acid (SA)-dependent defense and display hypersensitive cell death to benzothiadiazole (BTH), a functional analogue of SA. Two Arabidopsis lines with T-DNA insertions in the ARF-like B1 (ARL-B1) gene are found to be hypersensitive to BTH. Unlike min7 plants, however, the ARL-B1 knockout plants are not compromised in BTH-induced defense. Thus, BTH hypersensitivity and deficient BTH-induced defense can be uncoupled. AvrPto is an effector that compromises plant cell wall-based defense. AvrPto interacts in the yeast two-hybrid system with the RabE1 GTPases, a family of Rab GTPases predicted to be involved in polarized secretion in Arabidopsis. I found that AvrPto interacts with wild type RAB-E1d and RAB-E1d-Q74L (predicted to be GTP bound and active) but not with RAB-E1d-S29N (predicted to be GDP-bound and inactive). To better understand the function of RabE1 in the cell, I used the yeast two-hybrid screen to identify two Arabidopsis interactors of RabE1, REI1 and REI2. REI1 is annotated as a receptor-like kinase, and REI2 contains a SEC14-like domain.
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- Title
- Study of Pseudomonas syringae effector protein HopM1 and its host target AtMIN7 implicated in vesicle trafficking in Arabidopsis thaliana
- Creator
- Lee, Young Nam
- Date
- 2009
- Collection
- Electronic Theses & Dissertations