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Title: Systematic analysis of the signal responsive gene regulatory network governing Myxococcus xanthus development
Creator: Saha, Shreya
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Studies of signal-induced gene expression in bacteria have contributed to understanding of how bacteria cope with environmental stress. As an extensively studied model, Myxococcus xanthus provides fascinating insights into how changes at the level of gene expression enable which bacteria to survive environmental insults such as nutrient limitation. Upon starvation M. xanthus cells glide into aggregates and form mounds that mature into fruiting bodies as some cells form spores. Previously, our...
Show moreStudies of signal-induced gene expression in bacteria have contributed to understanding of how bacteria cope with environmental stress. As an extensively studied model, Myxococcus xanthus provides fascinating insights into how changes at the level of gene expression enable which bacteria to survive environmental insults such as nutrient limitation. Upon starvation M. xanthus cells glide into aggregates and form mounds that mature into fruiting bodies as some cells form spores. Previously, our group defined 24-30 h poststarvation as the critical period for commitment to spore formation, when cells commit to form spores despite perturbation of the starvation signal by nutrient addition. The process of multicellular development that culminates in sporulation is governed by a network of signal-responsive transcription factors that integrate signals for starvation and cellular alignment. In this dissertation I present the first systematic approach to elucidate the network dynamics during the commitment period.In the network, MrpC is a starvation-responsive transcription factor, whereas FruA is a transcription factor that responds to cellular alignment conveyed by C-signaling. Transcription of fruA is dependent on MrpC binding, and FruA activity is proposed to be posttranslationally regulated by C-signaling, although the mechanism is unknown. FruA and MrpC cooperatively regulate transcription of the dev operon. My systematic analysis of the network dynamics supported a model in which posttranslational activation of FruA by C-signaling is critical for dev transcription and for commitment to spore formation. Similar to dev, MrpC and C-signal-activated FruA combinatorially controlled transcription of the late-acting fadIJ operon involved in spore metabolism. Regulation of late-acting operons implicated in spore coat biogenesis (exoA-I, nfsA-H, MXAN_3259-MXAN_3263) was discovered to be under complex control by MrpC and FruA. My evidence suggests that transcription of these operons depends at least in part on a C-signal-dependent switch from negative regulation by unactivated FruA to positive regulation by activated FruA during the period leading up to and including commitment to sporulation. MrpC negatively regulated exo and MXAN_3259 during mound formation, but positively regulated nfs. During commitment to sporulation, MrpC continued to positively regulate nfs, switched to positive regulation of MXAN_3259, and continued to negatively regulate exo. A third transcription factor, Nla6, appeared to be a positive regulator of all the late genes. We propose that in combination with regulation by Nla6, differential regulation by FruA in response to C-signaling and by MrpC controls late gene expression to ensure that spore resistance and surface characteristics meet environmental demands.
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Title: A nitrogen-responsive small peptide signaling mechanism modulates plant root system architecture
Creator: Lay-Pruitt, Katerina Sibala
Date: 2021
Collection: Electronic Theses & Dissertations
Description: The plant root system changes dynamically in response to environmental cues. Plants utilize their root system for uptake of essential mineral nutrients that are heterogeneously distributed in the soil environment. Nutrient-dependent modulation of root system architecture (RSA) traits such as primary root growth, lateral root emergence, and the angles at which these roots grow allows for optimization of nutrient acquisition. Among signaling pathways by which plants may sense the availability...
Show moreThe plant root system changes dynamically in response to environmental cues. Plants utilize their root system for uptake of essential mineral nutrients that are heterogeneously distributed in the soil environment. Nutrient-dependent modulation of root system architecture (RSA) traits such as primary root growth, lateral root emergence, and the angles at which these roots grow allows for optimization of nutrient acquisition. Among signaling pathways by which plants may sense the availability of nutrients from the environment, small signaling peptide (SSP) pathways play important roles in optimizing root functions. These SSP pathways may further regulate molecular processes underlying RSA, such as the biosynthesis and transport of the major plant growth hormone, auxin. Characterization of these nutrient-responsive SSP pathways is thus of great importance and critical for understanding plant development in nutrient-poor environments. For my dissertation, I have identified and characterized a nitrogen (N)-responsive SSP pathway modulating root gravitropic response and lateral root development. Co-regulation of these RSA components by this module is proposed to prevent root outgrowth into N-poor regions and drive deeper root growth towards mobile nitrate (NO3-) resources stratified deeper in the soil profile. First, I show that a signaling pathway involving the CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) family of peptides and the CLAVATA1 (CLV1) receptor kinase, which is involved in N-dependent repression of lateral root emergence, also enhances root gravitropic response under N-limited conditions. Transcriptomic profiling of a clv1 mutant and CLE3 overexpressing lines identified Arabidopsis thaliana CENTRORADIALIS (ATC), a mobile protein previously characterized for its role in flowering regulation, as a downstream target of CLE-CLV1 signaling. Loss of ATC function significantly weakens root gravitropic response and has a moderate impact on lateral root emergence under low NO3- availability. ATC promoter activity and protein localization are also detected throughout the phloem and in the root columella cells, which are major centers for gravity sensing. Second, I demonstrate the relevance of ATC function on the molecular processes underlying root gravitropic response. While mutation in ATC does not impact gravity sensing via amyloplast sedimentation, it does inhibit the asymmetric transport of auxin needed for gravitropic bending. I determine that this occurs via the significant reduction of the PIN3 auxin efflux transporter in the vasculature and root tip of atc mutant lines. Lastly, I examine how the known roles of ATC in floral development could be implicated in root developmental processes. ATC binds to phosphatidic acid and phosphatidylserine, which is contrary to the binding capacity of its homolog FLOWERING LOCUS T (FT) to phosphatidylcholine and may contribute to its activity in N-limited environments. I also investigate the interaction of ATC and the transcription factor FD in the transcriptional regulation of PIN3. Although FD appears to have an impact on root gravitropic response, FD inhibits the expression of PIN3, suggesting potentially complex control of this gene via floral regulatory components. Taken together, the results presented in this dissertation contribute greatly to our understanding of how plant root architecture alters in response to N. These results can be further utilized in plant engineering strategies to regulate root growth in nutrient-limited soils.
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Title: USING FRAGARIA AS A MODEL SYSTEM FOR THE STUDY OF SUBGENOME DOMINANCE AND ADAPTATION IN CROPS
Creator: Alger, Elizabeth
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Polyploidy, or the presence of three or more complete genomes in a single organism, has occurred frequently in plants, especially in the angiosperm lineage. Allopolyploids, or polyploids resulting from the merging of different genomes in an interspecific hybrid, have often been shown to experience subgenome dominance. Subgenome dominance is the phenomenon where there is bias in the gene loss and expression between the different genomes in a polyploid, known as subgenomes. Despite the...
Show morePolyploidy, or the presence of three or more complete genomes in a single organism, has occurred frequently in plants, especially in the angiosperm lineage. Allopolyploids, or polyploids resulting from the merging of different genomes in an interspecific hybrid, have often been shown to experience subgenome dominance. Subgenome dominance is the phenomenon where there is bias in the gene loss and expression between the different genomes in a polyploid, known as subgenomes. Despite the prevalence of polyploids and subgenome dominance, little is known about the factors and mechanisms that influence this process. Strawberry (Fragaria sp.) is emerging as a powerful model system to investigate polyploid subgenome dominance evolution due to the recent identification of the four extant diploid progenitor species of the cultivated octoploid strawberry (Fragaria x ananassa). Having the diploid progenitors in hand allows us to identify differences between the dominant subgenome, F. vesca, and the other three progenitors that may have an impact of subgenome dominance. One possible factor is transposable element (TE) abundance, as low TE density has been consistently associated with the dominant subgenome in allopolyploids. Epigenetic silencing of TEs by DNA methylation to suppress TE activity has been shown to result in decreased expression of neighboring genes and this lowered gene expression may affect the establishment of subgenome dominance. F. vesca will be used as a diploid model for the study of subgenome dominance in strawberry where I can examine how TE abundance and other factors influence gene expression in a single accession and in hybrid crosses between different accessions. Tracking changes in gene expression in the hybrids will allow us to examine how genomes with difference sizes and genomic factors interact. The results and insights observed from this study can then be applied to subgenome dominance research in octoploid strawberry. In addition to the germplasm and genomic resources, strawberries are also a high value crop and the loss of their production due to (a)biotic stressors results in the loss of millions of United States dollars annually. Using a population of octoploid strawberries segregating for salt tolerance, I will identify candidate genes related to salt tolerance. Together this work will identify factors and mechanisms related to subgenome dominance and use genotypic data in a practical breeding context.
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Title: Reducing iron on a knife's edge - genomic and mechanistic studies of (hyper)thermophilic dissimilatory iron-reducing bacteria and archaea
Creator: Manzella, Michael P.
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Some members of the Bacteria and the Archaea have the rare ability to transfer electrons beyond the surface of their cells. This extracellular electron transfer permits the reduction of otherwise inaccessible electron acceptors such as insoluble Fe(III) oxides. The mechanisms that enable this ability have direct implications for geochemical cycles today and for life on early Earth. The physical settings present on early Earth, hot and influenced primarily by hydrothermal activity, can be...
Show moreSome members of the Bacteria and the Archaea have the rare ability to transfer electrons beyond the surface of their cells. This extracellular electron transfer permits the reduction of otherwise inaccessible electron acceptors such as insoluble Fe(III) oxides. The mechanisms that enable this ability have direct implications for geochemical cycles today and for life on early Earth. The physical settings present on early Earth, hot and influenced primarily by hydrothermal activity, can be found in rare sites on modern Earth. These sites most often surround deep-sea hydrothermal vents. Organisms present at these sites thrive, in most cases, absent of the sun’s influence. Instead of primary production from photosynthetic microorganisms, these communities rest on the shoulders of chemoautolithotrophic bacteria and archaea. Two of these organisms, the thermophilic bacterium Geothermobacter ehrlichii and the hyperthermophilic archaeon Geoglobus ahangari were selected to undergo genome and physiological characterization to determine how they interact with the abundant insoluble Fe(III) oxides found at hydrothermal vents. Both genomes were sequenced and, while only the genome of G. ahangari was complete, this permitted identification of critical components for iron respiration. In addition, mechanistic studies were performed on G. ahangari to elucidate a direct-contact mechanism of iron reduction. Finally, the extracellular filaments from these microorganisms were characterized and the more abundant filaments, in both organisms, were found to be conductive. These are the first examples of nanowires discovered outside of the mesophilic bacteria. In addition, the phylogenetic and geographic diversity between these isolates suggests that microbial nanowires are more widespread than previously thought.
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Title: An investigation of the transcriptional dynamics during the Pseudoperonospora cubensis - Cucumis sativus interaction
Creator: Burkhardt, Alyssa Kay
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Downy mildew of cucumber (Cucumis sativus) is caused by the obligate oomycete, Pseudoperonospora cubensis, and the research described in the dissertation provides new insight on the transcriptional regulation within the pathogen through the mechanism of alternative splicing and investigates the transcriptional changes of the host genes within a resistant and susceptible interaction. Previously, the genome of cucumber and P. cubensis as well transcriptome of a compatible interaction between...
Show moreDowny mildew of cucumber (Cucumis sativus) is caused by the obligate oomycete, Pseudoperonospora cubensis, and the research described in the dissertation provides new insight on the transcriptional regulation within the pathogen through the mechanism of alternative splicing and investigates the transcriptional changes of the host genes within a resistant and susceptible interaction. Previously, the genome of cucumber and P. cubensis as well transcriptome of a compatible interaction between the plant and the pathogen were sequenced. In addition, one gene from P. cubensis was known to be alternatively spliced, but the breadth of alternative splicing across the transcriptome was unknown. Through the work described in this thesis, we investigated the breadth of alternative splicing across the entire transcriptome of P. cubensis over the time course of infection. We found P. cubensis genes are frequently spliced and have intron retention as the most common mechanism of alternative splicing with some evidence for the retention of the 5' or 3' end of the exon but no evidence for exon skipping. Furthermore, we found that alternative splicing occurred in genes encoding several types of proteins, including the effectors, which impact pathogenicity and virulence. In some cases, the frequency of alternative splicing was found to correlate with developmental stages of the pathogen and thus alternative splicing might play a role in regulating transcript abundance and availability during development.Advances in sequencing and bioinformatics also contributed to our work in advancing the knowledge of the transcriptomic changes in a resistant (PI 197088) or susceptible (Vlaspik) plant during an infection time course. Our work shows that while P. cubensis is able to enter the resistant plant leaf, it is not able to sporulate; in contrast, the pathogen is able to grow and sporulate in the susceptible host, Vlaspik. To investigate the transcriptional changes underlying resistance, we identified the differentially expressed genes between the resistant and susceptible plant lines over the time course of infection. We found that the resistant plant responded earlier to the pathogen, as demonstrated by a higher number of differentially expressed genes at earlier time points compared to the susceptible plant. In addition, we found changes in genes encoding proteins with functions in hormone-related processes, nutrition, and transportation that might indicate a role for some of these genes in initiating or responding to the resistance response in cucumber. Beyond identifying differentially expressed transcripts, we identified small RNAs in the host and pathogen, as small RNAs have a role in modifying gene expression. We found novel miRNAs in the pathogen and known and novel miRNA in the host and predicted potential targets for each miRNA within the cucumber transcriptome. Some of these miRNAs may have a role in mediating the response of the plant to the pathogen. In the future, work will be done to validate the roles of candidate resistance-associated genes and to validate the presence and role of miRNA in both the host and the pathogen. Some of this future work will involve incorporating other “omics” methods including metabolomics and proteomics in order to get a more complete understanding of the molecular changes in the plant during infection. Finally, strong candidates for resistance could be validated using the proposed in planta methods, which includes the development of transgenic cucumbers.
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Title: CNGB1 mutation in papillon dogs : the identification, characterization and cure
Creator: Winkler, Paige A.
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Progressive retinal atrophy (PRA) is an inherited retinal dystrophy that affects over 100 breeds of dogs. It is characterized by a bilateral retinal degeneration commonly resulting in blindness. Affected dogs typically present with loss of dim light vision, attenuation of retinal blood vessels and tapetal hyperreflectivity. The purpose of this study was to identify the underlying cause of PRA in Papillon dogs and to characterize the phenotype at the cellular and molecular levels. I identified...
Show moreProgressive retinal atrophy (PRA) is an inherited retinal dystrophy that affects over 100 breeds of dogs. It is characterized by a bilateral retinal degeneration commonly resulting in blindness. Affected dogs typically present with loss of dim light vision, attenuation of retinal blood vessels and tapetal hyperreflectivity. The purpose of this study was to identify the underlying cause of PRA in Papillon dogs and to characterize the phenotype at the cellular and molecular levels. I identified a mutation in the gene CNGB1 which accounts for 70% of the PRA in the Papillon dogs. The CNGB1 mutation involves a 6 base pair insertion and a 1 base pair deletion resulting in exon skipping and a premature stop codon cause by a frameshift. CNGB1 encodes the β-subunit of a cyclic nucleotide-gated ion (CNG) channel. CNGB1 has multiple splice variants expressed in rod photoreceptors, olfactory sensory neurons and other tissues. CNG channels are directly involved in rod phototransduction and olfactory transduction. The retinal phenotype of the CNGB1 affected dogs was characterized by in vivo and ex vivo analyses. Electroretinograms (ERGs) and behavioral vision testing were conducted to assess retinal function throughout the course of the disease. The CNGB1 affected dogs had decreased and abnormal rod function at the earliest age tested but cone function was preserved until 5.5 years of age. Histological analyses showed that the morphology of rod photoreceptors deteriorate slowly over the first ~1.5 years of life while cone photoreceptor morphology is preserved for longer.Adeno-associated viral (AAV) vector therapy was used to treat five CNGB1 affected dogs with a wild-type copy of canine CNGB1 cDNA. One eye was injected with a low titer (1x1012) of an AAV vector delivering CNGB1 cDNA, six eyes were injected with a higher titer (5x1012) and one eye was injected with a GFP-expressing construct as a vehicle and procedural control. All dogs treated with the AAV vector containing the wild-type copy of CNGB1 showed rescue of rod function that was maintained throughout the time course of the study (9 months).The CNGB1 affected dog olfactory phenotype was investigated using in vivo and ex vivo techniques. The olfactory epithelium and the olfactory bulbs were abnormal in the CNGB1 affected dogs when compared to control dogs. I developed a behavioral test that could assess olfactory function in the CNGB1 dogs. The CNGB1 affected dogs had decreased but not absent olfactory function. The detailed descriptions of the retinal and olfactory phenotypes, in addition to the successful gene replacement therapy trial, in the CNGB1 affected dogs have laid the ground work for future studies including working with clinicians to advance gene replacement therapy trials in human patients with mutations in the CNGB1 gene.
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Title: The response of symbiotic zooxanthellae (Symbiodinium spp.) diversity and gene expression to stress in geographically distinct reefs
Creator: Hauff Salas, Briana Patricia
Date: 2015
Collection: Electronic Theses & Dissertations
Description: The persistence of coral reefs in the Florida Keys reef tract is of concern as coral bleaching, due to increased ocean temperatures, and human-linked disease outbreaks have led to a reduction in coral cover of 40% since the 1980’s. Evidence suggests a variation in stress susceptibility of conspecific coral from inshore and offshore reefs in the Florida Keys. However, the mechanism behind the disparity in stress susceptibility is unknown. Variation in genetic composition of a coral’s symbiotic...
Show moreThe persistence of coral reefs in the Florida Keys reef tract is of concern as coral bleaching, due to increased ocean temperatures, and human-linked disease outbreaks have led to a reduction in coral cover of 40% since the 1980’s. Evidence suggests a variation in stress susceptibility of conspecific coral from inshore and offshore reefs in the Florida Keys. However, the mechanism behind the disparity in stress susceptibility is unknown. Variation in genetic composition of a coral’s symbiotic algae (Symbiodinium spp.; referred to as zooxanthellae) has been proposed as a mechanism to withstand stress. As such, I investigated zooxanthellae composition of Porites astreoides and Montastraea cavernosa from an inshore and offshore reef in the Lower Florida Keys to determine links to stress susceptibility. Additionally, I investigated variation in the expression of metabolically related genes in zooxanthellae of P. astreoides reciprocally transplanted between reefs, as well as exposed to elevated temperatures and disease. Chapter one examines changes in the dominant zooxanthellae subclade type in P. astreoides and M. cavernosa throughout a two-year reciprocal transplant study. The goal of this study was to determine if zooxanthellae subclade type could explain higher rates of bleaching in offshore reef coral, as well as assessing the possibility of acclimatization to different environments. Increased complexity and diversity was seen in the composition of zooxanthellae subclade types from coral collected at offshore reefs, compared to inshore reefs. As a result, offshore reef zooxanthellae displayed less stability, possibly explaining higher bleaching susceptibility. Additionally, zooxanthellae composition patterns were retained throughout the reciprocal transplant, demonstrating a lack of acclimatization. Chapter two examined site-specific variation in the expression of metabolically related genes in zooxanthellae from P. astreoides following the reciprocal transplant. Symbionts from offshore corals experienced significantly increased expression in PCNA, SCP2, G3PDH, PCP and psaE (p<0.05) compared to inshore symbionts, a pattern consistent with increased bleaching susceptibility. Significant differences in gene expression between zooxanthellae from inshore and offshore reef indicate functional variability and are likely a result of localized adaptation. Similar to results in chapter one, gene expression patterns from site of origin were retained throughout the reciprocal transplant, suggesting no acclimatization. Chapter three investigated variation in the response of the same zooxanthellae genes when P. astreoides was exposed to extreme temperatures and disease. Here disease was mimicked by the application of lipopolysaccharide from Serratia marcescens, the causative agent of acroporid serratosis. Gene expression did not differ in zooxanthellae from inshore and offshore reefs, nor as a consequence of extreme temperature or disease. Several factors may explain the lack of variation including zooxanthellae response to acute versus moderate stress, host protection and targeting of symbionts by S. marcescens. These results suggest that symbionts of P. astreoides may be locally adapted to chronic moderate stress, but respond similarly to acute extreme conditions.
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Title: Kernel-based nonparametric testing in high-dimensional data with applications to gene set analysis
Creator: He, Tao, Ph. D.
Date: 2015
Collection: Electronic Theses & Dissertations
Description: The ultimate goal of genome-wide association studies (GWAS) is understanding the underlying relationship between genetic variants and phenotype. While the heretability is largely missing in univariate analysis of traditional GWAS, it is believed that the joint analysis of variants, that are interactively functioning in a biological pathway (gene set), is more beneficial in detecting association signals. With the fast developing pace of sequencing techniques, more detailed human genome...
Show moreThe ultimate goal of genome-wide association studies (GWAS) is understanding the underlying relationship between genetic variants and phenotype. While the heretability is largely missing in univariate analysis of traditional GWAS, it is believed that the joint analysis of variants, that are interactively functioning in a biological pathway (gene set), is more beneficial in detecting association signals. With the fast developing pace of sequencing techniques, more detailed human genome variation will be observed and hence the dimension of variants in the pathway could be extremely high. To model the systematic mechanism and the potential nonlinear interactions among the variants, in this dissertation we propose to model the set effect though a flexible non-parametric function under the high-dimensional setup, which allows the dimension goes to infinity as the size goes to infinity.Chapter 2 considers testing a nonparametric function of high-dimensional variates in a reproducing kernel Hilbert space (RKHS), which is a function space generated by a positive definite or semidefinite kernel function. We propose a test statistic to test the nonparametric function under the high-dimensional setting. The asymptotic distributions of the test statistic are derived under the null hypothesis and a series of local alternative hypotheses, the explicit power formula under which are also provided. We also develop a novel kernel selection procedure to maximize the power of the proposed test, as well as a kernel regularization procedure to further improve power. Extensive simulation studies and a real data analysis were conducted to evaluate the performance of the proposed method.Chapter 3 is theoretical investigation on the statistical optimality of kernel-based test statistic under the high-dimensional setup, from the minimax point of view. In particularly, we consider a high-dimensional linear model as the initial study. Unlike the sparsity or independence assumptions existing in related literature, we discussed the minimax properties under a structure free setting. We characterize the boundary that separates the testable region from the non-testable region, and show the rate-optimality of the kernel-based test statistic, under certain conditions on the covariance matrix and the growing speed of dimension.Our work in Chapter 4 fills the blank of kernel-based test using multiple candidate kernels under the high dimensional setting. Firstly, we extend the test statistic proposed in Chapter 2 to an inclusive form that allows the adjustment of covariants. The asymptotic distribution of the new test statistic under the null hypothesis is then provided. Two practical and efficient strategies are developed to incorporate multiple kernel candidates into the testing procedures. Through comprehensive simulation studies we show that both strategies can calibrates the type I error rate and improve the power over the the poor choice of kernel candidate in the set. Particularly, the maximum method, one of the two strategies, is shown having potential to boost the power close to one using the best candidate kernel. An application to Thai baby birth weight data further demonstrates the merits of our proposed methods.
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Title: Lipid trafficking and lipid breakdown in Chlamydomonas
Creator: Warakanont, Jaruswan
Date: 2015
Collection: Electronic Theses & Dissertations
Description: With their high photosynthetic efficiency and the ability to synthesize triacylglycerol (TAG), unicellular microalgae have an important ecological role, as well as value for production of triacylglycerol lipids that can be converted to biodiesel. The recent state of knowledge about microalgal lipid metabolism had been deduced from that of a model seed plant, Arabidopsis. However, recent studies have revealed that aspects of lipid metabolism differ between microalgae and Arabidopsis....
Show moreWith their high photosynthetic efficiency and the ability to synthesize triacylglycerol (TAG), unicellular microalgae have an important ecological role, as well as value for production of triacylglycerol lipids that can be converted to biodiesel. The recent state of knowledge about microalgal lipid metabolism had been deduced from that of a model seed plant, Arabidopsis. However, recent studies have revealed that aspects of lipid metabolism differ between microalgae and Arabidopsis. Investigating these differences was a cornerstone of this study, using Chlamydomonas, a representative of microalgae, and Arabidopsis. Two major approaches were undertaken: forward and reverse genetics. The forward genetic screening used insertional mutagenesis of Chlamydomonas and focused on a knockout mutation of a gene, which proved to be an orthologue of the Arabidopsis TRIGALACTOSYLDIACYLGLYCEROL 2 (TGD2). The tgd2 mutant exhibits increases in cellular concentrations of phosphatidic acid (PtdOH) and triacylglycerol (TAG); the latter contains signature fatty acids of monogalactosyldiacylglycerol (MGDG), pointing to its likely origin of synthesis. The mutant also experiences low viability in extended culture. Similar to AtTGD2, CrTGD2 is located in the chloroplast inner envelope membrane and binds PtdOH in vitro. Radioactive labeling experiments suggest that CrTGD2 functions in transferring a lipid precursor, presumably PtdOH, from the outer chloroplast envelope into the chloroplast. This study shows that, in contrast to prevailing assumptions, Chlamydomonas is able to import lipids from the endoplasmic reticulum (ER) to the chloroplast, and utilizes the eukaryotic pathway to synthesize galactoglycerolipids. The reverse genetics investigation focused on CrLIP4, a putative TAG lipase. CrLIP4 is an orthologue of a major Arabidopsis TAG lipase. Reverse transcription PCR revealed that the CrLIP4 transcript is reduced in abundance during N deprivation when TAG accumulates. Down-regulation of this gene through an artificial microRNA construct resulted in delayed TAG degradation. Expression of CrLIP4 in Escherichia coli alters the pattern of neutral lipids. Recombinant CrLIP4 exhibited TAG lipase activity. These results show that CrLIP4 has TAG lipase activity both in in vitro and in vivo. In summary, two Arabidopsis orthologues in Chlamydomonas were characterized through forward and reverse genetic approaches. The results elaborate and refine our understanding of Chlamydomonas lipid metabolism, and are likely relevant for other unicellular microalgae.
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Title: Determining the role of IRF6 in oogenesis and extra embryonic development
Creator: Smith, Arianna L.
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Interferon Regulatory Factor 6 (IRF6) is a member for the IRF family of transcription factors. Mutations in IRF6 cause two autosomal dominant Mendelian disorders characterized by cleft lip and palate. In addition, DNA variation in IRF6 contributes risk for non-syndromic cleft lip and palate. Mouse models developed to study Irf6 function indicate a critical role in regulation of proliferation and differentiation of keratinocytes during embryogenesis. Irf6 has also been implicated in adult...
Show moreInterferon Regulatory Factor 6 (IRF6) is a member for the IRF family of transcription factors. Mutations in IRF6 cause two autosomal dominant Mendelian disorders characterized by cleft lip and palate. In addition, DNA variation in IRF6 contributes risk for non-syndromic cleft lip and palate. Mouse models developed to study Irf6 function indicate a critical role in regulation of proliferation and differentiation of keratinocytes during embryogenesis. Irf6 has also been implicated in adult developmental processes and adult diseases. These include mammary development, breast cancer, squamous cell carcinoma, and wound healing. In addition, Irf6 has been implicated in a number of processes surrounding reproduction. Namely, studies using ovine models indicate a role for Irf6 in trophoblast cell types, the cell lineage that composes the placenta. Irf6 was also found to be expressed in bovine oocytes, indicating that it is a maternally expressed gene. Maternal expression of irf6 is conserved in zebrafish and frog. Inhibition of maternally deposited Irf6 in zebrafish resulted in early embryonic lethality. The aim of this work was to elucidate the role of maternally expressed Irf6 in early embryonic development and to study the function of Irf6 in placental development. To study the function of Irf6, a novel conditional allele of Irf6, carrying LoxP sites in introns two and four, was generated. This allele is important because Irf6-deficient mice die shortly after birth, precluding the study of gene function in postnatal development and disease. We validated the functionality of the conditional allele of Irf6 using three Cre transgenic lines: Gdf9-Cre, CAG-Cre and Ella-Cre. These Cre lines drive Cre expression in the oocyte or in early pre-implantation stages. Cre-mediated recombination of the conditional allele was sufficient to produce a null allele of Irf6. However, not all Cre transgenic lines were able to facilitate recombination with the same efficiency. We conclude that the Irf6 conditional allele is a novel tool for analysis of Irf6 function in a tissues specific manner. However, special consideration should be taken when selecting transgenic Cre lines.The conditional allele of Irf6, in combination with the Gdf9-Cre transgenic line, was utilized to generate mice with oocyte specific deletion of Irf6. Genetic analysis of progeny indicated that Gdf9-Cre efficiently recombined the Irf6 conditional allele in oocytes prior to meiosis I. Female mice with this oocyte specific excision of Irf6 displayed two novel phenotypes. First, these females displayed an increase in litter size when compared to control counterparts. Moreover, this increase in litter size was accompanied by an increase in ovulation. However, no difference in ovarian follicle numbers was observed. Females with oocyte specific excision of Irf6 also displayed an increase in multiple oocyte follicles (MOFs). These MOFs did not appear to contribute to the observed increase in ovulation. Most notably, MOFs are caused by impaired breakdown of germ cell nest. Irf6 expression was observed at critical time points in germ cell nest breakdown. This expression pattern suggests that Irf6 plays a role in germ cell nest breakdown. From this work, a novel role for Irf6 in regulating female fertility and folliculogenesis was identified. The mechanisms underlying these phenotypes have not yet been elucidated. Lastly, a conventional knockout mouse model was used to study the role of Irf6 in placental development. Irf6 expression was observed in the mouse placenta during embryogenesis. Analysis of Irf6-deficient and wildtype placenta was conducted. We observed no morphological differences in Irf6-deficient placenta. Along with this, there was no difference in wet weights between Irf6-deficient and wildtype embryos, suggesting normal placental function. We conclude that there is a non-essential role for Irf6 in placental development.
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Title: Sexual differentiation of the zebra finch neural song circuit
Creator: Beach, Linda Qi
Date: 2014
Collection: Electronic Theses & Dissertations
Description: The Australian zebra finch is an advantageous model for investigatingmechanisms regulating neural structure and behavior. Males and females exhibit remarkable differences in brain morphology and in the song behavior that they subserve. Thus, we can exploit these sexually dimorphic traits to begin to understand the factors that underlie development of the nervous system. While early studies implicated a critical role of estradiol (E2) in masculinizing both structure and function, Z-linked...
Show moreThe Australian zebra finch is an advantageous model for investigatingmechanisms regulating neural structure and behavior. Males and females exhibit remarkable differences in brain morphology and in the song behavior that they subserve. Thus, we can exploit these sexually dimorphic traits to begin to understand the factors that underlie development of the nervous system. While early studies implicated a critical role of estradiol (E2) in masculinizing both structure and function, Z-linked genes (males: ZZ; females: ZW) might also contribute. In the experiments conducted for this dissertation, I investigated the role of one Z-gene, tubulin specific chaperone protein A (TBCA) and its potential interactions with E2, in masculinizing the zebra finch song system. TBCA is one of several chaperone proteins involved in the formation of β-tubulin, and is critical for microtubule biosynthesis and integrity.I show that TBCA exhibits male-biased expression in the lateral magnocellularnucleus of the anterior nidopallium (LMAN). I also find that TBCA transcript and its protein product are developmentally regulated, such that this expression is higher in juveniles compared to adults. Further, TBCA is expressed in neurons that project to an efferent target, the robust nucleus of the arcopallium (RA). While the morphology of LMAN is not particularly different between the sexes, the projection from LMAN to RA is more robust in males, and this might influence masculine development of RA. Thus, TBCA is both temporally and spatially primed to influence sex-specific development.TBCA expression does not appear to be modulated by E2, as administration ofthis hormone did not influence TBCA mRNA quantity or stereological cell counts of TBCA+ cells in LMAN. However, treatment of males with the aromatase inhibitor, fadrozole, induced a hypermasculine phenotype in neural structures, including in the volume of LMAN, cell size in RA, and of the projection between these two regions.Finally, TBCA knockdown in LMAN in vivo demasculinized these samemorphological parameters in both males and females. Moreover, I did not detect an interaction between TBCA and E2 in facilitating masculine development, nor did I observe an additive effect of the two factors. Collectively, the present body of work represents an initial effort in determining the role of a Z-gene in the development of brain and behavior. The results here serve as an important platform from which wecan begin to explore the mechanisms regulating the observed effects, including those underlying cell survival and maintenance of neural projections.
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Title: The roles of C/EBPbeta and c-Jun in transcription of the gene encoding the murine progesterone receptor
Creator: Do, Han Ngoc
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Progesterone (P) and its receptor, the progesterone receptor (PR), are important for mammary gland development. Moreover, P/PR signaling also contributes to mammary tumorigenesis. Thus, studying the mechanism of PR expression is important in breast cancer research. C/EBPB-deficient mice and mice blocked for AP-1 activity show similar defects in mammary gland development as do PRB-deficient mice, especially during pregnancy, suggesting that these transcription factors might act in the same...
Show moreProgesterone (P) and its receptor, the progesterone receptor (PR), are important for mammary gland development. Moreover, P/PR signaling also contributes to mammary tumorigenesis. Thus, studying the mechanism of PR expression is important in breast cancer research. C/EBPB-deficient mice and mice blocked for AP-1 activity show similar defects in mammary gland development as do PRB-deficient mice, especially during pregnancy, suggesting that these transcription factors might act in the same pathway or may regulate overlapping sets of downstream target genes. An overall decrease in PR observed in sexually mature wild type mice fails to occur in C/EBPB-deficient mice, while no alterations in C/EBPB expression are observed in PR-deficient mice. Moreover, AP-1 has been found to regulate PR expression. These observations suggest that C/EBPB and AP-1 act upstream of PR. This leads us to study the possibility that C/EBPB and AP-1 are required for PR expression.We examined whether C/EBPB participated in the transcriptional regulation of PR expression in the mammary gland. Transient co-transfection of a PR promoter-reporter construct with expression vectors that individually express C/EBPB isoforms (LAP1, LAP2, or LIP) into a mouse mammary carcinoma cell line revealed that all C/EBPB isoforms, surprisingly including LIP (the shortest isoform lacking transactivation domains), can transactivate the PR promoter. Importantly, we found that LIP, in particular, robustly synergizes with an AP-1 member, c-Jun, to drive PR transcription. Consistent with significant roles for C/EBPB and c-Jun in PR expression, knockdown experiments showed that endogenous levels of C/EBPB and c-Jun expression were sufficient to drive the PR promoter-reporter. Additionally, overexpression of LIP elevated PR protein expression from the intact endogenous gene encoding PR. Furthermore, in vivo immunofluorescence studies showed that C/EBPB and PRA expression are mutually exclusive in the mammary epithelium, while PRB is only expressed in cells that express C/EBPB. This suggests an important role for C/EBPB in PRB expression during pregnancy. Then, we studied the mechanism by which LIP and c-Jun synergistically activate the PR promoter. We demonstrated in the reporter assay that the integrity of C/EBP- and AP-1-binding sites was required for the respective C/EBPB; and c-Jun activities on the PR promoter. Moreover, we showed in ChIP assay that efficient promoter occupancy of both LIP and c-Jun and their synergistic transactivation of the PR promoter required at least one C/EBP- and one AP-1-binding site. In addition, as indicating in the sequential ChIP assay, C/EBPB and c-Jun simultaneously occupied PR promoter. This leads us to propose a model where the synergy of C/EBPB and c-Jun in transactivation of the PR promoter is dependent on the two factors mutually stabilizing their recruitment to the PR promoter. Collectively, our data suggest a critical role for C/EBPB, particularly LIP, in PRB expression.
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Title: Investigating the role of the essential GTPase RbgA in the assembly of the large ribosomal subunit in Bacillus subtilis
Creator: Gulati, Megha
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Ribosomes are large ribonucleoprotein complexes required for synthesis of proteins and are a major target of several types of antibiotics. Ribosome assembly defects have been linked to several diseases, most notably Diamond-Blackfan anemia and Schwachman-Diamond syndrome. Although ribosome assembly has been studied extensively through in vitro reconstitution analysis, relatively little is known about the steps involved in vivo. Assembly factors such as...
Show moreRibosomes are large ribonucleoprotein complexes required for synthesis of proteins and are a major target of several types of antibiotics. Ribosome assembly defects have been linked to several diseases, most notably Diamond-Blackfan anemia and Schwachman-Diamond syndrome. Although ribosome assembly has been studied extensively through in vitro reconstitution analysis, relatively little is known about the steps involved in vivo. Assembly factors such as GTPases are a crucial universal requirement for ribosome assembly yet their precise role has remained elusive. This thesis focuses on characterization of RbgA (ribosome biogenesis GTPase A), an essential GTPase in Bacillus subtilis, and its role in the assembly of the large ribosomal subunit. RbgA is widely distributed evolutionarily and its homologs have been functionally implicated in ribosome assembly in yeast (Lsg1p, Nog2p and Nug1p) as well as mammalian cells (Mtg1). Analysis of the ribosome assembly intermediate isolated from RbgA-depleted cells indicated that the GTPase plays a crucial role at a late stage in maturation of the 50S subunit and in recruitment of r-proteins L16, L27 and L36 during the assembly process. To elucidate the role of RbgA in 50S assembly, first, we performed extensive biochemical analysis to determine the kinetic parameters of RbgA and its interaction with the 50S subunit and ribosomal intermediates (Chapter 2). These studies revealed that RbgA requires K+ ion for optimal GTPase activity and this activity is enhanced ~60 fold only in the presence of mature 50S subunit, and laid the groundwork for developing a model for the role of RbgA in the 50S assembly process. Next, we generated a library of loss-of-function mutant RbgA proteins through site-directed mutagenesis and performed kinetic analyses and biochemical characterization to delineate the critical functional sites of the enzyme (Chapter 3). To analyze the mutations in vivo, we engineered B. subtilis strains to express mutated RbgA protein(s) and analyzed the ribosomal intermediates formed in the cells. These studies identified a potential catalytic residue of RbgA and provided insight into its catalytic mechanism when complexed with its ribosomal substrate. Further, we identified and characterized an RNA-binding domain required for RbgA function. Lastly, we designed a genetic suppressor screen, and isolated, and characterized six independent extragenic suppressor mutations that partially alleviated the growth defect in the RbgA-defective B. subtilis strain (Chapter 4). These studies revealed a novel in vivo ribosomal intermediate and determined a functional interaction between RbgA and r-protein L6. Together, these studies provide a model for the molecular mechanism of RbgA interaction with the 50S ribosomal subunit and the role of the enzyme in the assembly process.
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Title: Role of waaL and umuDC in Erwinia amylovora EA1189 in oxidative stress and ultraviolet radiation survival
Creator: Berry, Matthew
Date: 2009
Collection: Electronic Theses & Dissertations

Title: Mechanisms mediating life history traits in the spotted hyena (Crocuta crocuta
Creator: Lewin, Nora Shannon
Date: 2017
Collection: Electronic Theses & Dissertations
Description: My dissertation focuses on understanding the mechanisms underpinning growth, reproduction, and survival in the spotted hyena. Following a general introductory chapter, my dissertation is composed of four independent research chapters. I begin with Chapter 2 in which my colleagues and I document a positive linear relationship between social dominance rank and telomere length. We also report significant variability in telomere length of high-ranking females among different social groups,...
Show moreMy dissertation focuses on understanding the mechanisms underpinning growth, reproduction, and survival in the spotted hyena. Following a general introductory chapter, my dissertation is composed of four independent research chapters. I begin with Chapter 2 in which my colleagues and I document a positive linear relationship between social dominance rank and telomere length. We also report significant variability in telomere length of high-ranking females among different social groups, suggesting that both social dominance rank and group membership influence this important biomarker of aging. In Chapter 3, we describe the role of juvenile concentrations of the hormone, insulin-like growth-factor -1 (IGF-1), in predicting trade-offs between early-life growth and later-life reproduction and survival among female hyenas. In Chapter 4, I explore IGF-1 as a potential mechanism of female-biased sexual size dimorphism by documenting sex-biased concentrations, sensitivities, and adaptive values of IGF-1 during the early postnatal period. Finally, in Chapter 5, I describe that age-related improvement and senescence in reproductive performance varies with social dominance rank among female hyenas. Cumulatively, my dissertation is an exploration of how physiological mechanisms may be used to understand social, physiological, and evolutionary forces operating in a free-living social carnivore. My work offers a unique contribution to the field of life-history evolution and furthers our understanding of the mechanisms that give rise to it.
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Title: GENOME BIOLOGY OF THE CULTIVATED POTATO, SOLANUM TUBEROSUM
Creator: Pham, Gina Mai
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Cultivated potato is a highly heterozygous, clonally propagated autotetraploid. These traits make it a difficult crop to study and make genetic improvements. In the following dissertation, I present studies that aim to improve our knowledge of genetic complexity in potato and potato breeding strategies. First, I show that several thousand genes in cultivated potato varieties show evidence of preferential allele expression, a characteristic not expected for autotetraploids. This trend was...
Show moreCultivated potato is a highly heterozygous, clonally propagated autotetraploid. These traits make it a difficult crop to study and make genetic improvements. In the following dissertation, I present studies that aim to improve our knowledge of genetic complexity in potato and potato breeding strategies. First, I show that several thousand genes in cultivated potato varieties show evidence of preferential allele expression, a characteristic not expected for autotetraploids. This trend was observed in evolutionarily conserved genes, suggesting that cultivated potato may have preferential expression of functional alleles. Cultivated potato also has excessive copy number variation. The results indicate that ~16-18,000 genes are copy number variable, and are evolutionarily recent and related to adaptation to biotic and abiotic stress. They are also lowly expressed, with only 528 genes showing correlation between copy number and gene expression. Second, a common method of genome reduction in potato, interspecific crossing, is explored to determine possible mechanisms by which genome elimination occurs and somaclonal variation which arises during the process. The results show that haploid inducer line, IVP101, produces <1% somatic translocation event frequency in the Superior dihaploid population studied. The translocation events occurred in regions of open chromatin, suggesting that they may be driven by transcription-coupled DNA repair. Finally, I present an improved potato genome assembly and annotation using a combination of long-read sequencing methods. The new assembly, DM v.5, is 727 Mb, of which 91% is contained in 12 chromosome-scale scaffolds. DM v.5 presents a new opportunity for studies in comparative genomics and potato biology.
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Title: Pervasive alternative RNA editing in Trypanosoma brucei
Creator: Kirby, Laura Elizabeth
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Trypanosoma brucei is a single celled eukaryote that utilizes a complex RNA editing system to render many of its mitochondrial genes translatable. Editing of these genes requires multiple small RNAs called guide RNAs to direct the insertion and deletion of uridines. These gRNAs act sequentially, each generating the anchor binding site for the next gRNA. This sequential dependence should render the process quite fragile, and mutations in the gRNAs should not be tolerated. In the examination...
Show more"Trypanosoma brucei is a single celled eukaryote that utilizes a complex RNA editing system to render many of its mitochondrial genes translatable. Editing of these genes requires multiple small RNAs called guide RNAs to direct the insertion and deletion of uridines. These gRNAs act sequentially, each generating the anchor binding site for the next gRNA. This sequential dependence should render the process quite fragile, and mutations in the gRNAs should not be tolerated. In the examination of the gRNA transcriptome of T. brucei, many gRNAs were identified that are capable of generating alternative mRNA sequences, and potentially disrupting the editing process. In this work, the effects of alternative editing are characterized. This analysis revealed the role of gRNAs in developmental regulation of gene expression, showing a correlation between the abundance of the initiating gRNAs across two different points in the life cycle of T. brucei and their expression. This study also revealed the existence of mitochondrial dual-coding genes, which provide protection for genetic material that is not under selection at all points of the life cycle of T. brucei. The examination of these dual-coding genes showed that RNA editing patterns can shift between cell lines and under different energetic conditions. Examining the gRNAs involved in these editing pathways revealed that there is a high amount of mismatching base pairs that are tolerated for editing to function, and that gRNA abundance is not a reliable predictor for editing preference. Finally, a reexamination of the gRNA transcriptome revealed that many gRNAs are still unidentified and most likely are generating new alternatively edited sequences."--Pages ii-iii.
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Title: Characterization of two large gene families in the sea lamprey
Creator: Chang, Steven
Date: 2013
Collection: Electronic Theses & Dissertations
Description: ABSTRACTCHARACTERIZATION OF TWO LARGE GENE FAMILIES IN THE SEA LAMPREYBySteven ChangThis dissertation employed molecular biology and bioinformatics to examine two large gene families in the sea lamprey, Petromyzon marinus. An integrative approach was used to define these gene families in order to ensure the validity of the size and members of each gene family. There are two chapters: Chapter 1 examines chemosensory gene expression in a specialized part of the olfactory system and Chapter 2...
Show moreABSTRACTCHARACTERIZATION OF TWO LARGE GENE FAMILIES IN THE SEA LAMPREYBySteven ChangThis dissertation employed molecular biology and bioinformatics to examine two large gene families in the sea lamprey, Petromyzon marinus. An integrative approach was used to define these gene families in order to ensure the validity of the size and members of each gene family. There are two chapters: Chapter 1 examines chemosensory gene expression in a specialized part of the olfactory system and Chapter 2 studies the expression of detoxification genes in the liver and gills in response to the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM).CHEMORECEPTOR GENESFor this dissertation, I will restrict chemoreception to the detection of chemical signals in the nose (note: chemoreception includes taste), and is accomplished by detection of odorants in the environment by specialized sensory cells in the main olfactory epithelium (MOE). In certain tetrapods, a second sensory epithelium is also found in the nose, called the vomeronasal organ (VNO). Canonically, each epithelium represents the start of different olfactory pathways, which govern different behavioral responses. Each epithelium expresses different classes of chemoreceptor (CR) genes; the MOE expresses odorant receptors (ORs) and trace amine-associated receptors (TAARs), while the VNO expresses ORs, vomeronasal type-1 and type-2 receptors (V1Rs and V2Rs). The sea lamprey olfactory organ has one nostril and so has one nasal capsule, which is divided into two spatially distinct regions: the main olfactory epithelium (MOE) and the accessory olfactory organ (AOO). The MOE has been well studied in lampreys but the function of the AOO has eluded description for over 100 years. Based on other research and due to its proximity to the MOE, we hypothesized that the AOO represents an ancestral VNO. If this AOO is indeed an ancestral VNO, we expect a different connectivity to the central nervous system than from the MOE, and would expect expression of pheromone receptors (V1Rs and V2Rs). CR expression in the MOE and AOO of sea lamprey were examined. The differential expression of CR genes between the two epithelia was determined and the connectivity of the main and accessory epithelia was determined using neural tract tracing. Quantitative PCR confirmed and quantified the differential expression of specific genes in the main and accessory olfactory epithelia.CYTOCHROME P450 GENESThe second gene family to be explored is the cytochrome P450 family. P450 genes encode for steroidogenic or detoxification enzymes that are inducible by a substrate. As part of the strategy for controlling sea lamprey populations TFM is applied to streams. Very little is known at the molecular level of how TFM works to kill sea lamprey larvae, but based on responses by other organisms to xenobiotic substances, our hypothesis is that P450 genes are induced by exposure to TFM. P450 genes were predicted from the sea lamprey genome and larvae were exposed to TFM and gill and liver tissues were harvested over an 8-hour time course. Expression was confirmed using high-throughput sequencing and quantitative PCR. The immediate goal was to determine which P450 genes are induced by exposure to TFM. Alternatively, we generated a list of predicted Phase II detoxification enzymes in the event that P450 genes showed no difference in expression. The long-term goal is to use that knowledge to design more efficient and specific lampricides.
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Title: Genome wide association study and genomic heritability of antimullerian hormone in dairy Holstein heifers
Creator: Nawaz, Muhammad Yasir
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "The objectives of this study were to estimate the genomic heritability of Anti Mullerian hormone (AMH), identify candidate genes associated with AMH production, and establish phenotypic correlations between serum AMH concentrations and parameters of reproductive performance in Holstein heifers. AMH concentrations were determined in 2905 dairy Holstein heifers. Animals were genotyped using the Zoetis 70K SNP Panel. Genotypes were imputed to standard USDA 60,671 bovine SNP set with 54,519 SNP...
Show more"The objectives of this study were to estimate the genomic heritability of Anti Mullerian hormone (AMH), identify candidate genes associated with AMH production, and establish phenotypic correlations between serum AMH concentrations and parameters of reproductive performance in Holstein heifers. AMH concentrations were determined in 2905 dairy Holstein heifers. Animals were genotyped using the Zoetis 70K SNP Panel. Genotypes were imputed to standard USDA 60,671 bovine SNP set with 54,519 SNP markers remaining after standard editing procedures. A linear mixed model was used to model the random effects of sampling day and genomics on the logarithm of AMH. Results showed that the genomic heritability (±SEM) of AMH was 0.36±0.03. We identified significant associations between AMH and 11 SNP markers on chromosome 11 and one marker on chromosome 20 based on a 5% false discovery rate. Some of the annotated genes in those regions have been previously identified as being important for AMH expression and ovarian function. There was no strong evidence of any association between conventional reproductive performance measures of dairy heifers and their serum AMH concentration. It seems that these associations should be studied in later parities as these heifers continue to mature. Nevertheless, the high heritability of AMH and a well-established association of AMH with super ovulatory response may make AMH a biomarker to genetically select cattle for larger gonads, more follicles and better response to superovulation."--Page ii.
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Title: The inheritance of a male sterile, apetalous inflorescence and narrow leaf shape in Zinnia elegans Jacq
Creator: Duffy, Robin Kay
Date: 1981
Collection: Electronic Theses & Dissertations

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