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Biology Department Faculty Works

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Articles 151 - 179 of 179

Full-Text Articles in Biology

Physiological Effects On Demography: A Long‐Term Experimental Study Of Testosterone’S Effects On Fitness, W. Reed, M. Clark, P. Parker, S. Raouf, N. Arguedas, D. Monk, E. Snajdr, V. Nolan, E. Ketterson Jan 2006

Physiological Effects On Demography: A Long‐Term Experimental Study Of Testosterone’S Effects On Fitness, W. Reed, M. Clark, P. Parker, S. Raouf, N. Arguedas, D. Monk, E. Snajdr, V. Nolan, E. Ketterson

Biology Department Faculty Works

Understanding physiological and behavioral mechanisms underlying the diversity of observed life‐history strategies is challenging because of difficulties in obtaining long‐term measures of fitness and in relating fitness to these mechanisms. We evaluated effects of experimentally elevated testosterone on male fitness in a population of dark‐eyed juncos studied over nine breeding seasons using a demographic modeling approach. Elevated levels of testosterone decreased survival rates but increased success of producing extra‐pair offspring. Higher overall fitness for testosterone‐treated males was unexpected and led us to consider indirect effects of testosterone on offspring and females. Nest success was similar for testosterone‐treated and control males, …

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Conservation Medicine On The Galápagos Islands: Partnerships Among Behavioral, Population, And Veterinary Scientists, Patricia Parker, Noah Whiteman, R. Miller Jan 2006

Conservation Medicine On The Galápagos Islands: Partnerships Among Behavioral, Population, And Veterinary Scientists, Patricia Parker, Noah Whiteman, R. Miller

Biology Department Faculty Works

No abstract provided.

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[Accepted Article Manuscript Version (Postprint)] Identification And Functional Characterization Of Arabidopsis Peroxin4 And The Interacting Protein Peroxin22, Bethany Zolman, Melanie Monroe-Augustus, Illeana Silva, Bonnie Bartel Dec 2005

[Accepted Article Manuscript Version (Postprint)] Identification And Functional Characterization Of Arabidopsis Peroxin4 And The Interacting Protein Peroxin22, Bethany Zolman, Melanie Monroe-Augustus, Illeana Silva, Bonnie Bartel

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Peroxins are genetically defined as proteins necessary for peroxisome biogenesis. By screening for reduced response to indole-3-butyric acid, which is metabolized to active auxin in peroxisomes, we isolated an Arabidopsis thaliana peroxin4 (pex4) mutant. This mutant displays sucrose-dependent seedling development and reduced lateral root production, characteristics of plant peroxisome malfunction. We used yeast two-hybrid analysis to determine that PEX4, an apparent ubiquitinconjugating enzyme, interacts with a previously unidentified Arabidopsis protein, PEX22. A pex4 pex22 double mutant enhanced pex4 defects, confirming that PEX22 is a peroxin. Expression of both Arabidopsis genes together complemented yeast pex4 or pex22 mutant defects, whereas expression …

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Climatic Unpredictability And Parasitism Of Caterpillars: Implications Of Global Warming, John Stireman, Lee Dyer, D. Janzen, M. Singer, J. Lill, R. Marquis, R. Ricklefs, G. Gentry, W. Hallwachs, P. Coley, J. Barone, H. Greeney, H. Connahs, P. Barbosa, H. Morais, I. Diniz Nov 2005

Climatic Unpredictability And Parasitism Of Caterpillars: Implications Of Global Warming, John Stireman, Lee Dyer, D. Janzen, M. Singer, J. Lill, R. Marquis, R. Ricklefs, G. Gentry, W. Hallwachs, P. Coley, J. Barone, H. Greeney, H. Connahs, P. Barbosa, H. Morais, I. Diniz

Biology Department Faculty Works

Insect outbreaks are expected to increase in frequency and intensity with projected changes in global climate through direct effects of climate change on insect populations and through disruption of community interactions. Although there is much concern about mean changes in global climate, the impact of climatic variability itself on species interactions has been little explored. Here, we compare caterpillar–parasitoid interactions across a broad gradient of climatic variability and find that the combined data in 15 geographically dispersed databases show a decrease in levels of parasitism as climatic variability increases. The dominant contribution to this pattern by relatively specialized parasitoid wasps …

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Flexible Social Structure Of A Desert Rodent, Rhombomys Opimus: Philopatry, Kinship, And Ecological Constraints, Jan Randall, Konstantin Rogovin, Patricia Parker, John Eimes Nov 2005

Flexible Social Structure Of A Desert Rodent, Rhombomys Opimus: Philopatry, Kinship, And Ecological Constraints, Jan Randall, Konstantin Rogovin, Patricia Parker, John Eimes

Biology Department Faculty Works

We tested hypotheses based on philopatry, kinship, and ecological constraints to explain sociality in a semifossorial desert rodent, the great gerbil, Rhombomys opimus. Data were collected in the field in Uzbekistan in the spring and fall of 1996 and 1998–2004. Population densities fluctuated dramatically with high turnover in both males and females to reveal that dispersal and social structure were density dependent. Fewer gerbils dispersed at higher densities and members of family groups dispersed together. A majority of females lived in groups at high densities, but as population densities declined, proportionally more females were solitary. DNA analysis revealed that group-living …

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Bateman Gradients In Field And Laboratory Studies: A Cautionary Tale, Patricia Parker, Zuleyma Tang-Martinez Nov 2005

Bateman Gradients In Field And Laboratory Studies: A Cautionary Tale, Patricia Parker, Zuleyma Tang-Martinez

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Since tools of molecular genetics became readily available, our understanding of bird mating systems has undergone a revolution. The majority of passerine species investigated are socially monogamous, but have been shown to be genetically polygamous. Data sets from natural populations of juncos suggest that multiple mating by females results in a sexual selection gradient as steep for females as for males (a result that does not support Bateman's predictions). However, in males, fitness is enhanced directly through fertilization success with multiple matings; in females fitness benefits may be enhanced immediately through direct access to food, protection against predators, or other …

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Regulatory Functions Of Phospholipase D And Phosphatidic Acid In Plant Growth, Development, And Stress Responses, Xuemin Wang Oct 2005

Regulatory Functions Of Phospholipase D And Phosphatidic Acid In Plant Growth, Development, And Stress Responses, Xuemin Wang

Biology Department Faculty Works

No abstract provided.

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Extrapair Fertilization And Genetic Similarity Of Social Mates In The Mexican Jay, John Eimes, Patricia Parker, Jerram Brown, Esther Brown Mar 2005

Extrapair Fertilization And Genetic Similarity Of Social Mates In The Mexican Jay, John Eimes, Patricia Parker, Jerram Brown, Esther Brown

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Inbreeding depression should favor the ability of females to avoid inbreeding or minimize its effects. We tested for a relationship between genetic similarity of social pairs and the occurrence of extrapair fertilization (EPF) in the Mexican jay (Aphelocoma ultramarina). Multilocus minisatellite and microsatellite DNA fingerprinting was used to detect extrapair young and measure genetic similarity between social parents. We found that 12 of 31 (39%) nests had at least one EPF and 15 of 93 (16%) young were the result of EPF. The mean DNA fingerprinting band sharing score between social mates who had at least one EPF was significantly …

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Correlational Selection Leads To Genetic Integration Of Body Size And An Attractive Plumage Trait In Dark-Eyed Juncos, Joel Mcglothlin, Patricia Parker, Val Nolan, Ellen Ketterson Jan 2005

Correlational Selection Leads To Genetic Integration Of Body Size And An Attractive Plumage Trait In Dark-Eyed Juncos, Joel Mcglothlin, Patricia Parker, Val Nolan, Ellen Ketterson

Biology Department Faculty Works

When a trait's effect on fitness depends on its interaction with other traits, the resultant selection is correlational and may lead to the integration of functionally related traits. In relation to sexual selection, when an ornamental trait interacts with phenotypic quality to determine mating success, correlational sexual selection should generate genetic correlations between the ornament and quality, leading to the evolution of honest signals. Despite its potential importance in the evolution of signal honesty, correlational sexual selection has rarely been measured in natural populations. In the dark‐eyed junco (Junco hyemalis), males with experimentally elevated values of a plumage trait (whiteness …

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Plant Ontology (Po): A Controlled Vocabulary Of Plant Structures And Growth Stages, Pankaj Jaiswal, Shulamit Avraham, Katica Ilic, Elizabeth Kellogg, Susan Mccouch, Anuradha Pujar, Leonore Reiser, Seung Rhee, Martin Sachs, Mary Schaeffer, Lincoln Stein, Peter Stevens, Leszek Vincent, Doreen Ware, Felipe Zapata Jan 2005

Plant Ontology (Po): A Controlled Vocabulary Of Plant Structures And Growth Stages, Pankaj Jaiswal, Shulamit Avraham, Katica Ilic, Elizabeth Kellogg, Susan Mccouch, Anuradha Pujar, Leonore Reiser, Seung Rhee, Martin Sachs, Mary Schaeffer, Lincoln Stein, Peter Stevens, Leszek Vincent, Doreen Ware, Felipe Zapata

Biology Department Faculty Works

The Plant Ontology Consortium (POC) (www.plantontology.org) is a collaborative effort among several plant databases and experts in plant systematics, botany and genomics. A primary goal of the POC is to develop simple yet robust and extensible controlled vocabularies that accurately reflect the biology of plant structures and developmental stages. These provide a network of vocabularies linked by relationships (ontology) to facilitate queries that cut across datasets within a database or between multiple databases. The current version of the ontology integrates diverse vocabularies used to describe Arabidopsis, maize and rice (Oryza sp.) anatomy, morphology and growth stages. Using the ontology browser, …

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Yeast Puf3 Mutants Reveal The Complexity Of Puf-Rna Binding And Identify A Loop Required For Regulation Of Mrna Decay, Wendy Olivas, S. Houshmandi Jan 2005

Yeast Puf3 Mutants Reveal The Complexity Of Puf-Rna Binding And Identify A Loop Required For Regulation Of Mrna Decay, Wendy Olivas, S. Houshmandi

Biology Department Faculty Works

The eukaryotic Puf proteins regulate mRNA translation and degradation by binding the 3' untranslated regions of target mRNAs. Crystal structure analysis of a human Puf bound to RNA suggested a modular mode of binding, with specific amino acids within each of eight repeat domains contacting a single nucleotide of the target RNA. Here we study the mechanism by which the yeast Puf3p binds and stimulates the degradation of COX17 mRNA. Mutation of the predicted RNA-binding positions of Puf3p to those found in Puf5p demonstrated that a single amino acid change in Puf3p abolished detectable binding to COX17. Since this amino …

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Profiling Condition-Specific, Genome-Wide Regulation Of Mrna Stability In Yeast, Wendy Olivas, B. Foat, S. Houshmandi, H. Bussemaker Jan 2005

Profiling Condition-Specific, Genome-Wide Regulation Of Mrna Stability In Yeast, Wendy Olivas, B. Foat, S. Houshmandi, H. Bussemaker

Biology Department Faculty Works

The steady-state abundance of an mRNA is determined by the balance between transcription and decay. Although regulation of transcription has been well studied both experimentally and computationally, regulation of transcript stability has received little attention. We developed an algorithm, MatrixREDUCE, that discovers the position-specific affinity matrices for unknown RNA-binding factors and infers their condition-specific activities, using only genomic sequence data and steady-state mRNA expression data as input. We identified and computationally characterized the binding sites for six mRNA stability regulators in Saccharomyces cerevisiae, which include two members of the Pumilio-homology domain (Puf) family of RNA-binding proteins, Puf3p and Puf4p. We …

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Evidence For And Characterization Of Ca2+ Binding To The Catalytic Region Of Arabidopsis Thaliana Phospholipase Dβ, Xuemin Wang Nov 2004

Evidence For And Characterization Of Ca2+ Binding To The Catalytic Region Of Arabidopsis Thaliana Phospholipase Dβ, Xuemin Wang

Biology Department Faculty Works

Most types of plant phospholipase D (PLD) require Ca2+ for activity, but how Ca2+ affects PLD activity is not well understood. We reported previously that Ca2+ binds to the regulatory C2 domain that occurs in the N terminus of the Ca2+-requiring PLDs. Using Arabidopsis thaliana PLDβ and C2-deleted PLDβ (PLDβcat), we now show that Ca2+ also interacts with the catalytic regions of PLD. PLDβcat exhibited Ca2+-dependent activity, was much less active, and required a higher level of Ca2+ than the full-length PLDβ. Ca2+ binding of the proteins was stimulated by phospholipids; phosphatidylserine was the most effective among those tested. Scatchard …

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Genetic Analysis Of Song Dialect Populations In Puget Sound White-Crowned Sparrows, Jill Soha, Douglas Nelson, Patricia Parker Jul 2004

Genetic Analysis Of Song Dialect Populations In Puget Sound White-Crowned Sparrows, Jill Soha, Douglas Nelson, Patricia Parker

Biology Department Faculty Works

The relationship between cultural variation and biological variation among natural populations has been the subject of both theoretical and empirical study. Zonotrichia leucophrys pugetensis is one of three subspecies of white-crowned sparrow known to form geographical song dialects. We investigated whether these dialects correspond to genetic differences among Z. l. pugetensis populations. We compared allele frequencies at four microsatellite loci in males from 11 sites spanning six dialects over the subspecies' range in Oregon and Washington. Cluster analysis and genotype assignment tests indicated no tendency for sample sites within dialect areas to be genetically more similar than are sites from …

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Genetic Control Of Branching In Foxtail Millet, Andrew Doust, Katrien Devos, Michael Gadberry, Mike Gale, Elizabeth Kellogg Jun 2004

Genetic Control Of Branching In Foxtail Millet, Andrew Doust, Katrien Devos, Michael Gadberry, Mike Gale, Elizabeth Kellogg

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Reduction in vegetative branching is commonplace when crops are domesticated from their wild progenitors. We have identified genetic loci responsible for these changes in foxtail millet (Setaria italica), a crop closely related to maize but whose genetics are little known. Quantitative trait locus (QTL) analysis and comparative genomics reveal that basal branching (tillering) and axillary branching are partially controlled by separate loci, and that the orthologue of teosinte branched1, the major gene controlling branching phenotype in maize, has only a minor and variable effect. We identify other candidate genes for control of branching, including a number of hormone biosynthesis pathway …

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Mer1p Is A Modular Splicing Factor Whose Function Depends On The Conserved U2 Snrnp Protein Snu17p, Marc Spingola, Javier Armisen, Manuel Ares Feb 2004

Mer1p Is A Modular Splicing Factor Whose Function Depends On The Conserved U2 Snrnp Protein Snu17p, Marc Spingola, Javier Armisen, Manuel Ares

Biology Department Faculty Works

Mer1p activates the splicing of at least three pre‐mRNAs (AMA1, MER2, MER3) during meiosis in the yeast Saccharomyces cerevisiae. We demonstrate that enhancer recognition by Mer1p is separable from Mer1p splicing activation. The C‐terminal KH‐type RNA‐binding domain of Mer1p recognizes introns that contain the Mer1p splicing enhancer, while the N‐terminal domain interacts with the spliceosome and activates splicing. Prior studies have implicated the U1 snRNP and recognition of the 5′ splice site as key elements in Mer1p‐activated splicing. We provide new evidence that Mer1p may also function at later steps of spliceosome assembly. First, Mer1p can activate splicing of introns …

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Recruitment Of The Puf3 Protein To Its Mrna Target For Regulation Of Mrna Decay In Yeast, Wendy Olivas, J. Jackson, S. Houshmandi, Leban Lopez Jan 2004

Recruitment Of The Puf3 Protein To Its Mrna Target For Regulation Of Mrna Decay In Yeast, Wendy Olivas, J. Jackson, S. Houshmandi, Leban Lopez

Biology Department Faculty Works

The Puf family of RNA-binding proteins regulates mRNA translation and decay via interactions with 3' untranslated regions (3' UTRs) of target mRNAs. In yeast, Puf3p binds the 3' UTR of COX17 mRNA and promotes rapid deadenylation and decay. We have investigated the sequences required for Puf3p recruitment to this 3' UTR and have identified two separate binding sites. These sites are specific for Puf3p, as they cannot bind another Puf protein, Puf5p. Both sites use a conserved UGUANAUA sequence, whereas one site contains additional sequences that enhance binding affinity. In vivo, presence of either site partially stimulates COX17 mRNA decay, …

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Metabolic Responses Of Shorebird Chicks To Cold Stress: Hysteresis Of Cooling And Warming Phases, Robert Ricklefs, Joseph Williams Aug 2003

Metabolic Responses Of Shorebird Chicks To Cold Stress: Hysteresis Of Cooling And Warming Phases, Robert Ricklefs, Joseph Williams

Biology Department Faculty Works

We developed a protocol for determining the maximum rate of oxygen consumption of shorebird chicks (Scolopacidae and Charadriidae) in response to cold challenge. We first subjected the chicks to gradually decreasing temperatures until their metabolism peaked and began to decrease. We ended the cooling phase of a trial when a chick’s body temperature Tb had declined typically to 32–34°C. After this point, we gradually increased the temperature in the metabolism chamber until normal Tb values and thermoneutral resting metabolism were restored. We refer to this cycle as the down–up (DU) protocol. We estimated instantaneous oxygen consumption (V . O∑) using …

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Biological Implications Of The Weibull And Gompertz Models Of Aging, Robert Ricklefs, Alex Scheuerlein Feb 2002

Biological Implications Of The Weibull And Gompertz Models Of Aging, Robert Ricklefs, Alex Scheuerlein

Biology Department Faculty Works

Gompertz and Weibull functions imply contrasting biological causes of demographic aging. The terms describing increasing mortality with age are multiplicative and additive, respectively, which could result from an increase in the vulnerability of individuals to extrinsic causes in the Gompertz model and the predominance of intrinsic causes at older ages in the Weibull model. Experiments that manipulate extrinsic mortality can distinguish these biological models. To facilitate analyses of experimental data, we defined a single index for the rate of aging (ω) for the Weibull and Gompertz functions. Each function described the increase in aging-related mortality in simulated ages at death …

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Test Of Intron Predictions Reveals Novel Splice Sites, Alternatively Spliced Mrnas And New Introns In Meiotically Regulated Genes Of Yeast, Carrie Davis, Leslie Grate, Marc Spingola, Manuel Ares Apr 2000

Test Of Intron Predictions Reveals Novel Splice Sites, Alternatively Spliced Mrnas And New Introns In Meiotically Regulated Genes Of Yeast, Carrie Davis, Leslie Grate, Marc Spingola, Manuel Ares

Biology Department Faculty Works

Correct identification of all introns is necessary to discern the protein-coding potential of a eukaryotic genome. The existence of most of the spliceosomal introns predicted in the genome of Saccharomyces cerevisiae remains unsupported by molecular evidence. We tested the intron predictions for 87 introns predicted to be present in non-ribosomal protein genes, more than a third of all known or suspected introns in the yeast genome. Evidence supporting 61 of these predictions was obtained, 20 predicted intron sequences were not spliced and six predictions identified an intron-containing region but failed to specify the correct splice sites, yielding a successful prediction …

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Genome-Wide Bioinformatic And Molecular Analysis Of Introns In Saccharomyces Cerevisiae, Marc Spingola, Leslie Grate, David Haussler, Manuel Ares Feb 1999

Genome-Wide Bioinformatic And Molecular Analysis Of Introns In Saccharomyces Cerevisiae, Marc Spingola, Leslie Grate, David Haussler, Manuel Ares

Biology Department Faculty Works

Introns have typically been discovered in an ad hoc fashion: introns are found as a gene is characterized for other reasons. As complete eukaryotic genome sequences become available, better methods for predicting RNA processing signals in raw sequence will be necessary in order to discover genes and predict their expression. Here we present a catalog of 228 yeast introns, arrived at through a combination of bioinformatic and molecular analysis. Introns annotated in the Saccharomyces Genome Database (SGD) were evaluated, questionable introns were removed after failing a test for splicing in vivo, and known introns absent from the SGD annotation were …

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The Roles Of Island Area Per Se And Habitat Diversity In The Species-Area Relationships Of Four Lesser Antillean Faunal Groups, Robert Ricklefs, Irby Lovette Jan 1999

The Roles Of Island Area Per Se And Habitat Diversity In The Species-Area Relationships Of Four Lesser Antillean Faunal Groups, Robert Ricklefs, Irby Lovette

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1. We analysed the relationships between species richness, island area, and habitat diversity for birds, bats, butterflies, and reptiles and amphibians on 19 islands in the Lesser Antilles. Habitat diversity was quantified by Simpson's index based on the total areas of five vegetation types on each island. Island area varied over two orders of magnitude (13–1510 km2) and habitat diversity varied between 1 and 3·7 equivalents of equally abundant habitat types.2. Because the Lesser Antilles consist of an inner arc of high, volcanic islands and an outer arc of low‐lying islands formed of uplifted marine sediments, correlations between area and …

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The Limits Of Specificity: An Experimental Analysis With Rna Aptamers To Ms2 Coat Protein Variants, Marc Spingola, Ichiro Hirao, David Peabody, Andrew Ellington Jan 1999

The Limits Of Specificity: An Experimental Analysis With Rna Aptamers To Ms2 Coat Protein Variants, Marc Spingola, Ichiro Hirao, David Peabody, Andrew Ellington

Biology Department Faculty Works

It has been hypothesized that selections for aptamers with high affinity for a given target molecule will of necessity identify aptamers that have high specificity for that target. We have attempted to assess this hypothesis by selecting aptamers that can bind to MS2 coat protein or to single- or double-substitution variants of the coat protein. Some aptamers selected to bind MS2 coat protein or its variants were mildly specific for their cognate targets, discriminating by two- to fourfold against closely related proteins. Specificity determinants on both the coat proteins and the aptamers could be identified. However, many aptamers could readily …

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Tapeinosperma Alatum (Myrsinaceae): A Remarkable New Species From Ceram, Diane Holland, P.F. Stevens Jan 1998

Tapeinosperma Alatum (Myrsinaceae): A Remarkable New Species From Ceram, Diane Holland, P.F. Stevens

Biology Department Faculty Works

A new pachycaul species Tapeinosperma alatum D.E. Holland & P.F. Stevens (Myrsinaceae) is described from South Central Ceram. It is characterized by its huge leaves, over 1 m long, and congested, almost Gunnera-like. inflorescence. The distinctive distribution of the Papuasian pachycaul species of Tapeinosperma is briefly compared with that of a number of other unrelated taxa.

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Ms2 Coat Protein Mutants Which Bind Qβ Rna, Marc Spingola, David Peabody Jul 1997

Ms2 Coat Protein Mutants Which Bind Qβ Rna, Marc Spingola, David Peabody

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The coat proteins of the RNA phages MS2 and Qβ are structurally homologous, yet they specifically bind different RNA structures. In an effort to identify the basis of RNA binding specificity we sought to isolate mutants that convert MS2 coat protein to the RNA binding specificity of Qβ. A library of mutations was created which selectively substitutes amino acids within the RNA binding site. Genetic selection for the ability to repress translation from the Qβ translational operator led to the isolation of several MS2 mutants that acquired binding activity for Qβ RNA. Some of these also had reduced abilities to …

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An Analysis Of The Variation Within Cratoxylum Arborescens (Clusiaceae) In Malesia, A.C. Church, P.F. Stevens Jan 1997

An Analysis Of The Variation Within Cratoxylum Arborescens (Clusiaceae) In Malesia, A.C. Church, P.F. Stevens

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The variation within the widespread West Malesian species Cratoxylum arborescens (Vahl) Blume was analyzed and three distinctive variants were found. These are recognized formally as varieties, var. arborescens, var. miquelii King, and var. borneense A.C. Church & P.F. Stevens. A key and full descriptions are given. The characters employed to delimit the three taxa are discussed and the selection of varietal rank is justified.

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The Rna-Binding Site Of Bacteriophage Qβ Coat Protein, Francis Lim, Marc Spingola, David Peabody Dec 1996

The Rna-Binding Site Of Bacteriophage Qβ Coat Protein, Francis Lim, Marc Spingola, David Peabody

Biology Department Faculty Works

The coat proteins of the RNA bacteriophages Qβ and MS2 are specific RNA binding proteins. Although they possess common tertiary structures, they bind different RNA stem loops and thus provide useful models of specific protein-RNA recognition. Although the RNA-binding site of MS2 coat protein has been extensively characterized previously, little is known about Qβ. Here we describe the isolation of mutants that define the RNA-binding site of Qβ coat protein, showing that, as with MS2, it resides on the surface of a large β-sheet. Mutations are also described that convert Qβ coat protein to the RNA binding specificity of MS2. …

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A Second Nitrogenase In Vegetative Cells Of A Heterocyst-Forming Cyanobacterium, T Thiel, E Lyons, J Erker, A Ernst Sep 1995

A Second Nitrogenase In Vegetative Cells Of A Heterocyst-Forming Cyanobacterium, T Thiel, E Lyons, J Erker, A Ernst

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In many filamentous cyanobacteria nitrogen fixation occurs in differentiated cells called heterocysts. Filamentous strains that do not form heterocysts may fix nitrogen in vegetative cells, primarily under anaerobic conditions. We describe here two functional Mo-dependent nitrogenases in a single organism, the cyanobacterium Anabaena variabilis. Using a lacZ reporter with a fluorescent beta-galactoside substrate for in situ localization of gene expression, we have shown that the two clusters of nif genes are expressed independently. One nitrogenase functions only in heterocysts under either aerobic or anaerobic growth conditions, whereas the second nitrogenase functions only under anaerobic conditions in vegetative cells and heterocysts. …

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Altering The Rna Binding Specificity Of A Translational Repressor, F Lim, Marc Spingola, D Peabody Mar 1994

Altering The Rna Binding Specificity Of A Translational Repressor, F Lim, Marc Spingola, D Peabody

Biology Department Faculty Works

The coat proteins of RNA phages MS2 and GA are specific RNA-binding proteins which function to encapsidate viral RNA and to translationally repress synthesis of the viral replicase. The two proteins have highly homologous amino acid sequences, yet they show different RNA binding specificities, recognizing RNA stem-loop structures which differ primarily in the nucleotide sequences of their loops. We sought to convert MS2 coat protein to the RNA binding specificity of GA through the introduction of GA-like amino acid substitutions into the MS2 coat protein RNA-binding site. The effects of the mutations were determined by measuring the affinity of the …

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