Life Sciences Commons^™

Calmodulin And Pf6 Are Components Of A Complex That Localizes To The C1 Microtubule Of The Flagellar Central Apparatus, Matthew J. Wargo, Erin E. Dymek, Elizabeth F. Smith

Dartmouth Scholarship

Studies of flagellar motility in Chlamydomonas mutants lacking specific central apparatus components have supported the hypothesis that the inherent asymmetry of this structure provides important spatial cues for asymmetric regulation of dynein activity. These studies have also suggested that specific projections associated with the C1 and C2 central tubules make unique contributions to modulating motility; yet, we still do not know the identities of most polypeptides associated with the central tubules. To identify components of the C1a projection, we took an immunoprecipitation approach using antibodies generated against PF6. The pf6 mutant lacks the C1a projection and possesses flagella that only …

Origin Of The Eumetazoa: Testing Ecological Predictions Of Molecular Clocks Against The Proterozoic Fossil Record, Kevin J. Peterson, Nicholas J. Butterfield

Dartmouth Scholarship

Molecular clocks have the potential to shed light on the timing of early metazoan divergences, but differing algorithms and calibration points yield conspicuously discordant results. We argue here that competing molecular clock hypotheses should be testable in the fossil record, on the principle that fundamentally new grades of animal organization will have ecosystem-wide impacts. Using a set of seven nuclear-encoded protein sequences, we demonstrate the paraphyly of Porifera and calculate sponge/eumetazoan and cnidarian/bilaterian divergence times by using both distance [minimum evolution (ME)] and maximum likelihood (ML) molecular clocks; ME brackets the appearance of Eumetazoa between 634 and 604 Ma, whereas …

Composite Genome Map And Recombination Parameters Derived From Three Archetypal Lineages Of Toxoplasma Gondii, Asis Khan, Sonya Taylor, Chunlei Su, Aaron J. Mackey, Jon Boyle, Robert Cole, Darius Glover, Keliang Tang, Ian T. Paulsen, Matt Berriman, John C. Boothroyd, Elmer K. Pfefferkorn, J P. Dubey, James W. Ajioka, David S. Roos, John C. Wootton, David Sibley

Dartmouth Scholarship

Toxoplasma gondii is a highly successful protozoan parasite in the phylum Apicomplexa, which contains numerous animal and human pathogens. T.gondii is amenable to cellular, biochemical, molecular and genetic studies, making it a model for the biology of this important group of parasites. To facilitate forward genetic analysis, we have developed a high-resolution genetic linkage map for T.gondii . The genetic map was used to assemble the scaffolds from a 10X shotgun whole genome sequence, thus defining 14 chromosomes with markers spaced at ∼300 kb intervals across the genome. Fourteen chromosomes were identified comprising a total genetic size of ∼592 cM …

A Gene Expression Fingerprint Of C. Elegans Embryonic Motor Neurons, Rebecca M. Fox, Stephen E. Von Stetina, Susan J. Barlow, Christian Shaffer, Kellen L. Olszewski, Jason H. Moore

Dartmouth Scholarship

Differential gene expression specifies the highly diverse cell types that constitute the nervous system. With its sequenced genome and simple, well-defined neuroanatomy, the nematode C. elegans is a useful model system in which to correlate gene expression with neuron identity. The UNC-4 transcription factor is expressed in thirteen embryonic motor neurons where it specifies axonal morphology and synaptic function. These cells can be marked with an unc-4::GFP reporter transgene. Here we describe a powerful strategy, Micro-Array Profiling of C. elegans cells (MAPCeL), and confirm that this approach provides a comprehensive gene expression profile of unc-4::GFP motor neurons in vivo.

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From The Cover: Assignment Of An Essential Role For The Neurospora Frequency Gene In Circadian Entrainment To Temperature Cycles, Antonio M. Pregueiro, Nathan Price-Lloyd, Deborah Bell-Pedersen, Christian Heintzen, Jennifer J. Loros, Jay C. Dunlap

Dartmouth Scholarship

Circadian systems include slave oscillators and central pacemakers, and the cores of eukaryotic circadian clocks described to date are composed of transcription and translation feedback loops (TTFLs). In the model system Neurospora, normal circadian rhythmicity requires a TTFL in which a White Collar complex (WCC) activates expression of the frequency (frq) gene, and the FRQ protein feeds back to attenuate that activation. To further test the centrality of this TTFL to the circadian mechanism in Neurospora, we used low-amplitude temperature cycles to compare WT and frq-null strains under conditions in which a banding rhythm was elicited. WT cultures were entrained …

Yos1p Is A Novel Subunit Of The Yip1p–Yif1p Complex And Is Required For Transport Between The Endoplasmic Reticulum And The Golgi Complex, Matthew Heidtman, Catherine Z. Chen, Ruth N. Collins, Charles Barlowe

Dartmouth Scholarship

Yeast Yip1p is a member of a conserved family of transmembrane proteins that interact with Rab GTPases. Previous studies also have indicated a role for Yip1p in the biogenesis of endoplasmic reticulum (ER)-derived COPII transport vesicles. In this report, we describe the identification and characterization of the uncharacterized open reading frame YER074W-A as a novel multicopy suppressor of the thermosensitive yip1-4 strain. We have termed this gene Yip One Suppressor 1 (YOS1). Yos1p is essential for growth and for function of the secretory pathway; depletion or inactivation of Yos1p blocks transport between the ER and …

Silencing Of Retrotransposons In Dictyostelium By Dna Methylation And Rnai, Markus Kuhlmann, Branimira E. Borisova, Markus Kaller, Pontus Larsson, Dirk Stach, Jianbo Na, Ludwig Eichinger, Frank Lyko, Victor Ambros, Fredrik Soderbom, Christian Hammann, Wolfgang Nellen

Dartmouth Scholarship

We have identified a DNA methyltransferase of the Dnmt2 family in Dictyostelium that was denominated DnmA. Expression of the dnmA gene is downregulated during the developmental cycle. Overall DNA methylation in Dictyostelium is ∼0.2% of the cytosine residues, which indicates its restriction to a limited set of genomic loci. Bisulfite sequencing of specific sites revealed that DnmA is responsible for methylation of mostly asymmetric C-residues in the retrotransposons DIRS-1 and Skipper. Disruption of the gene resulted in a loss of methylation and in increased transcription and mobilization of Skipper. Skipper transcription was also upregulated in strains that had genes encoding …

Crystal Structure Of The Gtpase Domain Of Rat Dynamin 1, Thomas F. Reubold, Susanne Eschenburg, Andreas Becker, Marilyn Leonard, Sandra L. Schmid, Richard B. Vallee, F. Jon Kull, Dietmar J. Manstein

Dartmouth Scholarship

Here, we present the 1.9-A crystal structure of the nucleotide-free GTPase domain of dynamin 1 from Rattus norvegicus. The structure corresponds to an extended form of the canonical GTPase fold observed in Ras proteins. Both nucleotide-binding switch motifs are well resolved, adopting conformations that closely resemble a GTP-bound state not previously observed for nucleotide-free GTPases. Two highly conserved arginines, Arg-66 and Arg-67, greatly restrict the mobility of switch I and are ideally positioned to relay information about the nucleotide state to other parts of the protein. Our results support a model in which switch I residue Arg-59 gates GTP binding …