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Articles 1 - 18 of 18
Full-Text Articles in Biology
Phylogenetics, Morpohology, And Genomic Evolution In Physarieae (Brassicaceae), Sara Fuentes-Soriano
Phylogenetics, Morpohology, And Genomic Evolution In Physarieae (Brassicaceae), Sara Fuentes-Soriano
Dissertations
The mustard family (Brassicaceae) is economically important but the evolution of its morphology is not well understood. I investigate the evolution of morphological and genomic characters and calculate ancestral trait values in the Brassicaceae within a phylogenetic context using the tribe Physarieae as a model system. Physarieae are a unique and diverse group of American mustards characterized by multi-aperturate pollen. Phylogenetic analyses of DNA sequences (chloroplast ndhF and nuclear ITS and LUMINIDEPENDENS) were used to test the monophyly and explore evolutionary relationships of Physarieae. The phylogenetic inferences were used to identify morphological traits to delimit the tribe, to interpret the …
Development Of A Methodology To Attain High Levels Of Storage Proteins In Cassava Tuberized Roots And Its Implications, Mohammad Abhary
Development Of A Methodology To Attain High Levels Of Storage Proteins In Cassava Tuberized Roots And Its Implications, Mohammad Abhary
Dissertations
Cassava (Manihot esculenta Crantz.) is a member of the Euphorbiaceae family, cultivated in the tropics and subtropical areas as a staple food crop for more than 700 million people around the world. The starchy storage roots of cassava are rich in calories and deficient in all other nutrients, cassava meals has the lowest of all sources of dietary protein. Severe protein deficiencies and malnutrition problems are common among those who rely on cassava as their daily meal. Although cassava is ranked the fifth most important crop in the world, the research on this crop is very limited. Among the limited …
Avian Developmental Endocrinology: The Effects And Role Of Yolk Hormones, Sibling Dynamics, And Life-History, Corinne Patricia Kozlowski
Avian Developmental Endocrinology: The Effects And Role Of Yolk Hormones, Sibling Dynamics, And Life-History, Corinne Patricia Kozlowski
Dissertations
Inter-specific variation of the endocrine system is an underlying component for variation in avian life-history. Females deposit hormones into the yolks of their eggs, and embryonic exposure affects nestling phenotype. Hormones are also produced endogenously by developing nestlings, further influencing their behavior and physiology. This dissertation examines the role of the endocrine system in development by focusing on several different avian taxa. Yolk hormone concentrations often vary across the laying order and may mediate hatching asynchrony. These patterns were characterized in two species that lay asynchronously hatching clutches: Eastern screech owls (Megascops asio) and cockatiels (Nymphicus hollandicus). The patterns described …
[Accepted Article Manuscript Version (Postprint)] Pex5 Mutants That Differentially Disrupt Pts1 And Pts2 Peroxisomal Matrix Protein Import In Arabidopsis, Bibi Khan, Bethany Zolman
[Accepted Article Manuscript Version (Postprint)] Pex5 Mutants That Differentially Disrupt Pts1 And Pts2 Peroxisomal Matrix Protein Import In Arabidopsis, Bibi Khan, Bethany Zolman
Biology Department Faculty Works
PEX5 and PEX7 are receptors required for the import of peroxisome-bound proteins containing one of two peroxisomal targeting signals (PTS1 or PTS2). To better understand the role of PEX5 in plant peroxisomal import, we characterized the Arabidopsis (Arabidopsis thaliana) pex5-10 mutant, which has a T-DNA insertion in exon 5 of the PEX5 gene. Sequencing results revealed that exon 5, along with the T-DNA, is removed in this mutant, resulting in a truncated pex5 protein. The pex5-10 mutant has germination defects and is completely dependent on exogenous Suc for early seedling establishment, based on poor utilization of seed-storage fatty acids. This …
Invasive Honeysuckle Eradication Reduces Tick-Borne Disease Risk By Altering Host Dynamics, Brian Allan, Humberto Dutra, Lisa Goessling, Kirk Barnett, Jonathan Chase, Robert Marquis, Genevieve Pang, Gregory Storch, Robert Thach, John Orrock
Invasive Honeysuckle Eradication Reduces Tick-Borne Disease Risk By Altering Host Dynamics, Brian Allan, Humberto Dutra, Lisa Goessling, Kirk Barnett, Jonathan Chase, Robert Marquis, Genevieve Pang, Gregory Storch, Robert Thach, John Orrock
Biology Department Faculty Works
Despite the ubiquity of invasive organisms and their often deleterious effects on native flora and fauna, the consequences of biological invasions for human health and the ecological mechanisms through which they occur are rarely considered. Here we demonstrate that a widespread invasive shrub in North America, Amur honeysuckle (Lonicera maackii), increases human risk of exposure to ehrlichiosis, an emerging infectious disease caused by bacterial pathogens transmitted by the lone star tick (Amblyomma americanum). Using large-scale observational surveys in natural areas across the St. Louis, Missouri region, we found that white-tailed deer (Odocoileus virginianus), a preeminent tick host and pathogen reservoir, …
Long-Term Isolation Of A Highly Mobile Seabird On The Galapagos, Patricia Parker, Frank Hailer, E.A. Schreiber, Joshua Miller, Iris Levin, R. Chesser, Robert Fleischer
Long-Term Isolation Of A Highly Mobile Seabird On The Galapagos, Patricia Parker, Frank Hailer, E.A. Schreiber, Joshua Miller, Iris Levin, R. Chesser, Robert Fleischer
Biology Department Faculty Works
The Galapagos Islands are renowned for their high degree of endemism. Marine taxa inhabiting the archipelago might be expected to be an exception, because of their utilization of pelagic habitats—the dispersal barrier for terrestrial taxa—as foraging grounds. Magnificent frigatebirds (Fregata magnificens) have a highly vagile lifestyle and wide geographical distribution around the South and Central American coasts. Given the potentially high levels of gene flow among populations, the species provides a good test of the effectiveness of the Galapagos ecosystem in isolating populations of highly dispersive marine species. We studied patterns of genetic (mitochondrial DNA, microsatellites and nuclear introns) and …
The Role Of Puf3p And Puf4p In The Regulation Of Mrna Decay In Yeast Saccharomyces Cerevisiae, Florencia Andrea Lopez Leban
The Role Of Puf3p And Puf4p In The Regulation Of Mrna Decay In Yeast Saccharomyces Cerevisiae, Florencia Andrea Lopez Leban
Dissertations
Proper regulation of gene expression at a cellular level is required in all organisms for their successful adaptation and survival to physiological or environmental changes. In eukaryotes, a convenient way of regulating gene expression is achieved by post-transcriptionally adjusting the decay rates of different mRNAs. The Puf family of proteins in yeast belong to a widespread group of eukaryotic RNA-binding proteins that regulate the lifespans of target mRNAs by sequence specifically binding to 3' untranslated regions (UTRs) and modulating their decay rates. For example, the yeast Puf3 protein binds the COX17 3' UTR, stimulating its deadenylation and subsequent decay. However, …
Aromatic Acid Metabolites Of Escherichia Coli K-12 Can Induce The Marrab Operon, Lon Chubiz, Christopher Rao
Aromatic Acid Metabolites Of Escherichia Coli K-12 Can Induce The Marrab Operon, Lon Chubiz, Christopher Rao
Biology Department Faculty Works
MarR is a key regulator of the marRAB operon involved in antibiotic resistance and solvent stress tolerance in Escherichia coli. We show that two metabolic intermediates, 2,3-dihydroxybenzoate and anthranilate, involved in enterobactin and tryptophan biosynthesis, respectively, can activate marRAB transcription. We also found that a third intermediate involved in ubiquinone biosynthesis, 4-hydroxybenzoate, activates marRAB transcription in the absence of TolC. Of the three, however, only 2,3-dihydroxybenzoate directly binds MarR and affects its activity.
Potential Biases In Estimating The Rate Parameter Of Sigmoid Growth Functions, Robert Ricklefs, Suzanne Austin, Tara Robinson, W. Robinson
Potential Biases In Estimating The Rate Parameter Of Sigmoid Growth Functions, Robert Ricklefs, Suzanne Austin, Tara Robinson, W. Robinson
Biology Department Faculty Works
1. We compare biases in estimates of the rate constant of the logistic and Gompertz functions applied to avian growth using three methods of parameter estimation. The methods differ in how the asymptote is determined, and consist of either floating asymptotes estimated from the full data (floating A) or data truncated at 70% of the adult mass (70%A), or fixing the asymptote at the adult mass (fixed A).2. First, using data for two passerine species exhibiting different growth patterns, we truncated mass measurements at different ages to explore how each method of growth rate estimation responded to simulated differences in …
Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar
Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar
Physics Faculty Works
The role of mutation rate in optimizing key features of evolutionary dynamics has recently been investigated in various computational models. Here, we address the related question of how maximum mutation size affects the formation of species in a simple computational evolutionary model. We find that the number of species is maximized for intermediate values of a mutation size parameter μ; the result is observed for evolving organisms on a randomly changing landscape as well as in a version of the model where negative feedback exists between the local population size and the fitness provided by the landscape. The same result …
Rna Processing Of Nitrogenase Transcripts In The Cyanobacterium Anabaena Variabilis, Justin Ungerer, Brenda Pratte, Teresa Thiel
Rna Processing Of Nitrogenase Transcripts In The Cyanobacterium Anabaena Variabilis, Justin Ungerer, Brenda Pratte, Teresa Thiel
Biology Department Faculty Works
Little is known about the regulation of nitrogenase genes in cyanobacteria. Transcription of the nifH1 and vnfH genes, encoding dinitrogenase reductases for the heterocyst-specific Mo-nitrogenase and the alternative V-nitrogenase, respectively, was studied by using a lacZ reporter. Despite evidence for a transcription start site just upstream of nifH1 and vnfH, promoter fragments that included these start sites did not drive the transcription of lacZ and, for nifH1, did not drive the expression of nifHDK1. Further analysis using larger regions upstream of nifH1 indicated that a promoter within nifU1 and a promoter upstream of nifB1 both contributed to expression of nifHDK1, …
Nonspecific Phospholipase C Npc4 Promotes Responses To Abscisic Acid And Tolerance To Hyperosmotic Stress In Arabidopsis, Xuemin Wang, Carlotta Peters, Maoyin Li, Rama Narasimhan, Mary Roth, Ruth Welti
Nonspecific Phospholipase C Npc4 Promotes Responses To Abscisic Acid And Tolerance To Hyperosmotic Stress In Arabidopsis, Xuemin Wang, Carlotta Peters, Maoyin Li, Rama Narasimhan, Mary Roth, Ruth Welti
Biology Department Faculty Works
Diacyglycerol (DAG) is an important class of cellular lipid messengers, but its function in plants remains elusive. Here, we show that knockout of the Arabidopsis thaliana nonspecific phospholipase C (NPC4) results in a decrease in DAG levels and compromises plant response to abscisic acid (ABA) and hyperosmotic stresses. NPC4 hydrolyzes various phospholipids in a calcium-independent manner, producing DAG and a phosphorylated head group. NPC4 knockout (KO) plants display decreased ABA sensitivity in seed germination, root elongation, and stomatal movement and had decreased tolerance to high salinity and water deficiency. Overexpression of NPC4 renders plants more sensitive to ABA and more …
Individuals Differences In Exploratory Behavior Of Prairie Voles, Microtus Ochrogaster, Danielle N. Lee
Individuals Differences In Exploratory Behavior Of Prairie Voles, Microtus Ochrogaster, Danielle N. Lee
Dissertations
Individual differences in behavior are significant because they serve as the substrate for natural selection. Within the Behavioral Syndromes framework, researchers study individual differences in behavior of animals. Behavioral Syndromes are defined as correlations between behaviors in different environmental contexts or testing situations. In this study, I examined the effects of litter size and sex ratio, familial relationships, and age and sex on exploratory behavior of prairie voles, Microtus ochrogaster. Exploratory behavior, defined as spontaneous behavioral responses to unfamiliar stimuli, was examined in three novel situations: an open-field with novel objects, a two-way novel choice apparatus, and a complex maze. …
Mate Choice For Genetic Quality: A Test Of The Heterozygosity And Compatibility Hypotheses In A Lek-Breeding Bird, T.B. Ryder, W.P. Tori, J.G. Blake, B.A. Loiselle, P.G. Parker
Mate Choice For Genetic Quality: A Test Of The Heterozygosity And Compatibility Hypotheses In A Lek-Breeding Bird, T.B. Ryder, W.P. Tori, J.G. Blake, B.A. Loiselle, P.G. Parker
Biology Department Faculty Works
Understanding female mate choice in nonresource-based mating systems, where females appear to express strong preferences despite receiving no direct benefits from mate choice, remain a challenge to behavioral ecology. Brown (Brown JL. 1997. A theory of mate choice based on heterozygosity. Behav Ecol. 8:60–65) proposed the “good-genes-as-heterozygosity” hypothesis, which sought to establish the genetic nature of male quality. Despite recent attention, few studies have examined how multiple components of genetic quality influence mate choice in a highly promiscuous mating system such as that of the lekking wire-tailed manakin (Pipra filicauda, Aves: Pipridae). Based on a 4-year study in the Amazon …
Comparative Gene Evolution In Haemosporidian (Apicomplexa) Parasites Of Birds And Mammals, Robert Ricklefs, Diana Outlaw
Comparative Gene Evolution In Haemosporidian (Apicomplexa) Parasites Of Birds And Mammals, Robert Ricklefs, Diana Outlaw
Biology Department Faculty Works
Haemosporidian parasites of birds and mammals reproduce asexually inside nucleated and nonnucleated host erythrocytes, respectively. Because of these different parasite environments and because bird parasites are paraphyletic, we evaluated whether patterns of parasite molecular evolution differ between host groups. We compared two mitochondrial (mt) genes and one apicoplast gene across mammal Plasmodium, bird Plasmodium, and bird Parahaemoproteus. Using a molecular phylogenetic approach, we show that the parasite mt cytochrome b (cyt b), mt cytochrome oxidase I (COI), and the apicoplast caseinolytic protease C (ClpC) exhibit similar levels of sequence divergence, yet each gene tree presents a strikingly different pattern of …
Domestic Exotics And The Perception Of Invasibility, Qinfeng Guo, Robert Ricklefs
Domestic Exotics And The Perception Of Invasibility, Qinfeng Guo, Robert Ricklefs
Biology Department Faculty Works
Susceptibility of an area to invasion by exotic species is often judged by the fraction of introduced species in the local biota. However, the degree of invasion, particularly in mainland areas, has often been underestimated because of the exclusion of ‘domestic exotics’ (those introduced to internal units from within the national border) in calculations. Because all introduced species on islands are considered as exotics, this contributes to the perception that islands are more susceptible to invasion than are continental regions. Here, we determine the contribution of domestic exotic species to the degree of invasion (exotic fraction) in mainland areas. We …
Insights From Comparative Analyses Of Aging In Birds And Mammals, Robert Ricklefs
Insights From Comparative Analyses Of Aging In Birds And Mammals, Robert Ricklefs
Biology Department Faculty Works
Many laboratory models used in aging research are inappropriate for understanding senescence in mammals, including humans, because of fundamental differences in life history, maintenance in artificial environments, and selection for early aging and high reproductive rate. Comparative studies of senescence in birds and mammals reveal a broad range in rates of aging among a variety of taxa with similar physiology and patterns of development. These comparisons suggest that senescence is a shared property of all vertebrates with determinate growth, that the rate of senescence has been modified by evolution in response to the potential life span allowed by extrinsic mortality …
Fur Versus Feathers: Pollen Delivery By Bats And Hummingbirds, And Consequences For Pollen Production, Nathan Muchhala, James Thomson
Fur Versus Feathers: Pollen Delivery By Bats And Hummingbirds, And Consequences For Pollen Production, Nathan Muchhala, James Thomson
Biology Department Faculty Works
One floral characteristic associated with bat pollination (chiropterophily) is copious pollen production, a pattern we confirmed in a local comparison of hummingbird- and bat-adapted flowers from a cloud forest site in Ecuador. Previous authors have suggested that wasteful pollen transfer by bats accounted for the pattern. Here we propose and test a new hypothesis: bats select for increased pollen production because they can efficiently transfer larger amounts of pollen, which leads to a more linear male fitness gain curve for bat-pollinated plants. Flight cage experiments with artificial flowers and flowers of Aphelandra acanthus provide support for this hypothesis; in both …