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Articles 1 - 12 of 12
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Convergence, Constraint And The Role Of Gene Expression During Adaptive Radiation: Floral Anthocyanins In Aquilegia, Justen B. Whittall, Claudia Voelckel, Daniel J. Kliebenstein, Scott A. Hodges
Convergence, Constraint And The Role Of Gene Expression During Adaptive Radiation: Floral Anthocyanins In Aquilegia, Justen B. Whittall, Claudia Voelckel, Daniel J. Kliebenstein, Scott A. Hodges
Biology
Convergent phenotypes are testament to the role of natural selection in evolution. However, little is known about whether convergence in phenotype extends to convergence at the molecular level. We use the independent losses of floral anthocyanins in columbines (Aquilegia) to determine the degree of molecular convergence in gene expression across the anthocyanin biosynthetic pathway (ABP). Using a phylogeny of the North American Aquilegia clade, we inferred six independent losses of floral anthocyanins. Via semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we monitored developmental and tissue-specific variation in expression of the six major structural ABP loci in three Aquilegia species, two that …
Influence Of Resource Pulses And Perennial Neighbors On The Establishment Of An Invasive Annual Grass In The Mojave Desert, Rebecca E. Drenovsky, J. J. James, M. A. Caird, R. L. Sheley
Influence Of Resource Pulses And Perennial Neighbors On The Establishment Of An Invasive Annual Grass In The Mojave Desert, Rebecca E. Drenovsky, J. J. James, M. A. Caird, R. L. Sheley
Biology
Invasion by exotic annual grasses is one of the most significant threats to arid ecosystems in the western USA. Current theories of invasibility predict plant communities become more susceptible to invasion whenever there is an increase in the amount of unused resources. The objective of this field study was to examine how resource pulses and temporal variation in resource demand by the native shrub vegetation influences establishment of the invasive annual grass Schismus arabicus. Water and nitrogen were applied as pulses in early spring, mid-spring, or continuously throughout the growing season to plots containing either Atriplex confertifolia or Atriplex …
The Evolution Of Organismal Complexity In Angiosperms As Measured By The Information Content Of Taxonomic Descriptions, J. Gordon Burleigh, Justen B. Whittall, Michael J. Sanderson
The Evolution Of Organismal Complexity In Angiosperms As Measured By The Information Content Of Taxonomic Descriptions, J. Gordon Burleigh, Justen B. Whittall, Michael J. Sanderson
Biology
We describe an information theoretic method for measuring relative organismal complexity. The complexity measure is based on the amount of information contained in formal taxonomic descriptions of organisms. We examine the utility of this measure for quantifying the complexity of plant families. The descriptions are subjective by nature, but we find a significant correlation in the complexity values of plant families from two independently authored sets of formal taxonomic descriptions. An analysis of the evolution of complexity across angiosperms found evidence of a pattern of increasing complexity. Our measure of complexity provides an operational definition of complexity that may be …
Soil Microbial Community Composition As Affected By Restoration Practices In California Grassland, Rebecca E. Drenovsky, Martin Pothoff, Kerri L. Steenwerth, Louise E. Jackson, Rainer G. Joergensen, Kate M. Scow
Soil Microbial Community Composition As Affected By Restoration Practices In California Grassland, Rebecca E. Drenovsky, Martin Pothoff, Kerri L. Steenwerth, Louise E. Jackson, Rainer G. Joergensen, Kate M. Scow
Biology
Agricultural practices have strong impacts on soil microbes including both the indices related to biomass and activity as well as those related to community composition. In a grassland restoration project in California, where native perennial bunchgrasses were introduced into non-native annual grassland after a period of intensive tillage, weeding, and herbicide use to reduce the annual seed bank, microbial community composition was investigated. Three treatments were compared: annual grassland, bare soil fallow, and restored perennial grassland. Soil profiles down to 80cm in depth were investigated in four separate layers (0–15, 15–30, 30–60, and 60–80cm) using both phospholipid ester-linked fatty acid …
Bacterial Cell Biology: Managing Magnetosomes, Craig Stephens
Bacterial Cell Biology: Managing Magnetosomes, Craig Stephens
Biology
Sensing of magnetic fields by living organisms — magnetosensing — is best understood in magnetotactic bacteria. Recently work has provided new insight into the biogenesis of bacterial magnetosomes, and links these organelles to a newly recognized prokaryotic cytoskeletal filament which organizes magnetosomes into a sensory structure capable of aligning cells with the geomagnetic field.
A Survey Of Nuclear Ribosomal Internal Transcribed Spacer Substitution Rates Across Angiosperms: An Approximate Molecular Clock With Life History Effects, Kathleen M. Kay, Justen B. Whittall, Scott A. Hodges
A Survey Of Nuclear Ribosomal Internal Transcribed Spacer Substitution Rates Across Angiosperms: An Approximate Molecular Clock With Life History Effects, Kathleen M. Kay, Justen B. Whittall, Scott A. Hodges
Biology
Background: A full understanding of the patterns and processes of biological diversification requires the dating of evolutionary events, yet the fossil record is inadequate for most lineages under study. Alternatively, a molecular clock approach, in which DNA or amino acid substitution rates are calibrated with fossils or geological/climatic events, can provide indirect estimates of clade ages and diversification rates. The utility of this approach depends on the rate constancy of molecular evolution at a genetic locus across time and across lineages. Although the nuclear ribosomal internal transcribed spacer region ( nrITS) is increasingly being used to infer clade ages in …
Relating The Cost Of Spinning Silk To The Tendency To Share It For Three Embiids With Different Lifestyles (Order Embiidina: Clothodidae, Notoligotomidae, And Australembiidae), Janice Edgerly-Rooks, Shailesh Shenoy, Vanessa Werner
Relating The Cost Of Spinning Silk To The Tendency To Share It For Three Embiids With Different Lifestyles (Order Embiidina: Clothodidae, Notoligotomidae, And Australembiidae), Janice Edgerly-Rooks, Shailesh Shenoy, Vanessa Werner
Biology
Although adult female embiids (Order Embiidina) superficially lack morphological diversity, their variety of habitats may impose distinct selective pressures on behavior, such as their use of silk and their tendency to aggregate. For example, where silk serves as a primary defense from environmental threats, coloniality might be adaptive. The cost of production or spinning might also prompt them to share silk. These ideas were tested in laboratory trials involving three species of embiids with different lifestyles: an arboreal species (Antipaluria urichi (Saussure) from a neotropical rain forest, a species (Notoligotoma hardyi (Frederichs) that dwells on surfaces of granite outcrops in …
Low Leaf N And P Resorption Contributes To Nutrient Limitation In Two Desert Shrubs, Rebecca E. Drenovsky, J. H. Richards
Low Leaf N And P Resorption Contributes To Nutrient Limitation In Two Desert Shrubs, Rebecca E. Drenovsky, J. H. Richards
Biology
Both water and nutrients are limiting in arid environments, and desert plants have adapted to these limitations through numerous developmental and physiological mechanisms. In the Mono Basin, California, USA, co-dominant Sarcobatus vermiculatus and Chrysothamnus nauseosus ssp. consimilis are differentially N and P limited. We hypothesized that low leaf N resorption contributes to N-limitation in Sarcobatus and that low leaf P resorption contributes to P-limitation in Chrysothamnus. As predicted, Sarcobatus resorbed proportionally 1.7-fold less N than Chrysothamnus, but reduced leaf P in senescent leaves to lower levels than Chrysothamnus (8.0–10.8-fold lower based on leaf area or mass, respectively), consistent with N, …
Mutant Neurogenin-3 In Congenital Malabsorptive Diarrhea, Jiafang Wang, Galen Cortina, S. Vincent Wu, Robert Tran, Jang-Hyeon Cho, Ming-Jer Tsai, Travis J. Bailey, Milan Jamrich, Marvin E. Ament, William R. Treem, Ivor D. Hill, Jorge H. Vargas, George Gershman, Douglas G. Farmer, Laurie Reyen, Martin G. Martín
Mutant Neurogenin-3 In Congenital Malabsorptive Diarrhea, Jiafang Wang, Galen Cortina, S. Vincent Wu, Robert Tran, Jang-Hyeon Cho, Ming-Jer Tsai, Travis J. Bailey, Milan Jamrich, Marvin E. Ament, William R. Treem, Ivor D. Hill, Jorge H. Vargas, George Gershman, Douglas G. Farmer, Laurie Reyen, Martin G. Martín
Biology
Background: Neurogenin-3 (NEUROG3) is expressed in endocrine progenitor cells and is required for endocrine-cell development in the pancreas and intestine. The NEUROG3 gene (NEUROG3) is therefore a candidate for the cause of a newly discovered autosomal recessive disorder characterized by generalized malabsorption and a paucity of enteroendocrine cells. Methods: We screened genomic DNA from three unrelated patients with sparse enteroendocrine cells for mutations of NEUROG3. We then tested the ability of the observed mutations to alter NEUROG3 function, using in vitro and in vivo assays. Results: The patients had few intestinal enteroendocrine cells positive for chromogranin A, but they had …
Modification Of Human Immunodeficiency Virus Type 1 Reverse Transcriptase To Target Cells With Elevated Cellular Dntp Concentrations, Varuni K. Jamburuthugoda, Pauline Chugh, Baek Kim
Modification Of Human Immunodeficiency Virus Type 1 Reverse Transcriptase To Target Cells With Elevated Cellular Dntp Concentrations, Varuni K. Jamburuthugoda, Pauline Chugh, Baek Kim
Biology
Retroviruses and DNA viruses utilize cellular dNTPs as substrates for their DNA polymerases during viral replication in infected cells. However, because of S phase-dependent dNTP biosynthesis, the availability of cellular dNTPs significantly varies among cell types (e.g. dividing versus nondividing cells and normal versus tumor cells). Here we tested whether alterations in the dNTP utilization efficiency and dNTP binding affinity of viral DNA polymerases can switch viral infection specificity to cell types with different dNTP concentrations. We employed an HIV-1 reverse transcriptase (RT) mutant (Q151N), which is catalytically active only at high dNTP concentrations because of its reduced dNTP binding …
Identification Of The Heparin-Binding Determinants Within Fibronectin Repeat Iii1: Role In Cell Spreading And Growth, Liqiong Gui, Katherine Wojciechowski, Candace D. Gildner, Hristina Nedelkovska, Denise C. Hocking
Identification Of The Heparin-Binding Determinants Within Fibronectin Repeat Iii1: Role In Cell Spreading And Growth, Liqiong Gui, Katherine Wojciechowski, Candace D. Gildner, Hristina Nedelkovska, Denise C. Hocking
Biology
Fibronectins are high molecular mass glycoproteins that circulate as soluble molecules in the blood, and are also found in an insoluble, multimeric form in extracellular matrices throughout the body. Soluble fibronectins are polymerized into insoluble extracellular matrix (ECM) fibrils via a cell-dependent process. Recent studies indicate that the interaction of cells with the ECM form of fibronectin promotes actin organization and cell contractility, increases cell growth and migration, and enhances the tensile strength of artificial tissue constructs; ligation of integrins alone is insufficient to trigger these responses. Evidence suggests that the effect of ECM fibronectin on cell function is mediated …
Krepa4, An Rna Binding Protein Essential For Editosome Integrity And Survival Of Trypanosoma Brucei, Rezaq Salavati, Nancy Lewis Ernst, Jeffrey O'Rear, Troy Gilliam, Salvador Tarun Jr., Kenneth Stuart, K.
Krepa4, An Rna Binding Protein Essential For Editosome Integrity And Survival Of Trypanosoma Brucei, Rezaq Salavati, Nancy Lewis Ernst, Jeffrey O'Rear, Troy Gilliam, Salvador Tarun Jr., Kenneth Stuart, K.
Biology
The 20S editosome, a multiprotein complex, catalyzes the editing of most mitochondrial mRNAs in trypanosomatids by uridylate insertion and deletion. RNAi mediated inactivation of expression of KREPA4 (previously TbMP24), a component of the 20S editosome, in procyclic form Trypanosoma brucei resulted in inhibition of cell growth, loss of RNA editing, and disappearance of 20S editosomes. Levels of MRP1 and REAP-1 proteins, which may have roles in editing but are not editosome components, were unaffected. Tagged KREPA4 protein is incorporated into 20S editosomes in vivo with no preference for either insertion or deletion subcomplexes. Consistent with its S1-like motif, recombinant KREPA4 …