Biology Commons^™

Functional Analysis Of Subunit E Of The F1FO-Atp Synthase Of The Yeast Saccharomyces Cerevisiae: Importance Of The N-Terminal Membrane Anchor Region, Valerie Everard-Gigot, Cory D. Dunn, Brigid M. Dolan, Susanne Brunner, Robert E. Jensen, Rosemary A. Stuart

Biological Sciences Faculty Research and Publications

Mitochondrial F₁F_o-ATP synthase complexes do not exist as physically independent entities but rather form dimeric and possibly oligomeric complexes in the inner mitochondrial membrane. Stable dimerization of two F₁F_o-monomeric complexes involves the physical association of two membrane-embedded F_o-sectors. Previously, formation of the ATP synthase dimeric-oligomeric network was demonstrated to play a critical role in modulating the morphology of the mitochondrial inner membrane. In Saccharomyces cerevisiae, subunit e (Su e) of the F_o-sector plays a central role in supporting ATP synthase dimerization. The Su e protein is anchored …

Elimination Of Foreign Dna During Somatic Differentiation In Tetrahymena Thermophila Shows Position Effect And Is Dosage Dependent, Yifan Liu, Xiaoyuan Song, Martin A. Gorovsky, Kathleen M. Karrer

Biological Sciences Faculty Research and Publications

In the ciliate Tetrahymena thermophila, approximately 15% of the germ line micronuclear DNA sequences are eliminated during formation of the somatic macronucleus. The vast majority of the internal eliminated sequences (IESs) are repeated in the micronuclear genome, and several of them resemble transposable elements. Thus, it has been suggested that DNA elimination evolved as a means for removing invading DNAs. In the present study, bacterial neo genes introduced into the germ line micronuclei were eliminated from the somatic genome. The efficiency of elimination from two different loci increased dramatically with the copy number of the neo genes in the …

Dimeric Novel Hsp40 Is Incorporated Into The Radial Spoke Complex During The Assembly Process In Flagella, Chun Yang, Mark M. Compton, Pinfen Yang

Biological Sciences Faculty Research and Publications

The radial spoke is a stable structural complex in the 9 + 2 axoneme for the control of flagellar motility. However, the spokes in Chlamydomonas mutant pf24 are heterogeneous and unstable, whereas several spoke proteins are reduced differentially. To elucidate the defective mechanism, we clone RSP16, a prominent spoke protein diminished in pf24 axonemes. Unexpectedly, RSP16 is a novel HSP40 member of the DnaJ superfamily that assists chaperones in various protein-folding-related processes. Importantly, RSP16 is uniquely excluded from the 12S spoke precursor complex that is packaged in the cell body and transported toward the flagellar tip to be …

The Bipartite Structure Of The Trna M1A58 Methyltransferase From S. Cerevisiae Is Conserved In Humans, Sarah G. Ozanick, Annette M. Krecic, Joshua Andersland, James T. Anderson

Biological Sciences Faculty Research and Publications

Among all types of RNA, tRNA is unique given that it possesses the largest assortment and abundance of modified nucleosides. The methylation at N₁ of adenosine 58 is a conserved modification, occurring in bacterial, archaeal, and eukaryotic tRNAs. In the yeast Saccharomyces cerevisiae, the tRNA 1-methyladenosine 58 (m¹A58) methyltransferase (Mtase) is a two-subunit enzyme encoded by the essential genes TRM6 (GCD10) and TRM61 (GCD14). While the significance of many tRNA modifications is poorly understood, methylation of A58 is known to be critical for maintaining the stability of initiator tRNA^Met in yeast. …

Contractile Responses Of The Rat Gastrocnemius And Soleus Muscles To Isotonic Resistance Exercise, Kris M. Norenberg, Robert H. Fitts

Biological Sciences Faculty Research and Publications

Male rats were divided into control and weight-trained (WT) groups. WT rats performed squattype exercises twice daily, 5 days/wk, for 14 wk. They averaged 36 lifts/day, with an average weight of 555 g. Muscle-to-body weight ratio (mg/g) of the soleus (Sol) was not different from control, but it increased 11 and 6% in the gastrocnemius (Gast) and plantaris, respectively (P < 0.05). The normalized twitch tension of the in situ Sol was elevated by 21%, whereas single-skinned type I fibers from the Sol showed an increased rate constant of tension redevelopment (K_tr) but no other contractile adaptations to WT. In contrast, the Gast type I fibers showed an increase (P < 0.05) in maximal velocity of shortening (25%), peak power (15%), K_tr (18%), and normalized tension (7%). The K_tr and normalized tension of the Gast type IIa fibers increased by …

Ic138 Is A Wd-Repeat Dynein Intermediate Chain Required For Light Chain Assembly And Regulation Of Flagellar Bending, Triscia W. Hendrickson, Catherine A. Perrone, Paul Griffin, Kristin Wuichet, Joshua Mueller, Pinfen Yang, Mary E. Porter, Winfield S. Sale

Biological Sciences Faculty Research and Publications

Increased phosphorylation of dynein IC IC138 correlates with decreases in flagellar microtubule sliding and phototaxis defects. To test the hypothesis that regulation of IC138 phosphorylation controls flagellar bending, we cloned the IC138 gene. IC138 encodes a novel protein with a calculated mass of 111 kDa and is predicted to form seven WD-repeats at the C terminus. IC138 maps near the BOP5 locus, and bop5-1 contains a point mutation resulting in a truncated IC138 lacking the C terminus, including the seventh WD-repeat. bop5-1 cells display wild-type flagellar beat frequency but swim slower than wild-type cells, suggesting that bop5-1 is altered in …

The Yeast Rrna Biosynthesis Factor Ebp2p Is Also Required For Efficient Nuclear Division, Costin N. Ionescu, Sofia Origanti, Michael A. Mcalear

Biological Sciences Faculty Research and Publications

Molecular genetic analysis of the yeast Ebp2 protein has revealed that it is an essential, nucleolar protein that functions in the rRNA biosynthesis pathway. Temperature-sensitive ebp2-1 mutants are defective in the processing of the 27 SA precursor rRNA, and the point substitutions that disrupt this activity cluster towards the central, more highly conserved region of the Ebp2 protein. We report here that other ebp2 mutants exhibit deficiencies associated with defects in chromosome segregation. Yeast cells bearing a 50 amino acid C-terminal truncation allele (ebp2ΔC50) display a slow-growth phenotype and exhibit an increased percentage of cells with …

Skeletal Muscle Fiber Atrophy: Altered Thin Filament Density Changes Slow Fiber Force And Shortening Velocity, Danny A. Riley, J. L. W. Bain, Janell Romatowski, Robert H. Fitts

Biological Sciences Faculty Research and Publications

Single skinned fibers from soleus and adductor longus (AL) muscles of weight-bearing control rats and rats after 14-day hindlimb suspension unloading (HSU) were studied physiologically and ultrastructurally to investigate how slow fibers increase shortening velocity (V₀) without fast myosin. We hypothesized that unloading and shortening of soleus during HSU reduces densities of thin filaments, generating wider myofilament separations that increase V₀ and decrease specific tension (kN/m²). During HSU, plantarflexion shortened soleus working length 23%. AL length was unchanged. Both muscles atrophied as shown by reductions in fiber cross-sectional area. For AL, the 60% atrophy …

Asymmetric Atp Binding And Hydrolysis Activity Of The Thermus Aquaticus Muts Dimer Is Key To Modulation Of Its Interactions With Mismatched Dna, Edwin Antony, Manju M. Hingorani

Biological Sciences Faculty Research and Publications

Prokaryotic MutS and eukaryotic Msh proteins recognize base pair mismatches and insertions or deletions in DNA and initiate mismatch repair. These proteins function as dimers (and perhaps higher order oligomers) and possess an ATPase activity that is essential for DNA repair. Previous studies of Escherichia coli MutS and eukaryotic Msh2−Msh6 proteins have revealed asymmetry within the dimer with respect to both DNA binding and ATPase activities. We have found the Thermus aquaticus MutS protein amenable to detailed investigation of the nature and role of this asymmetry. Here, we show that (a) in a MutS dimer one subunit (S1) binds nucleotide …

Reticulospinal Neurons Receive Direct Spinobulbar Inputs During Locomotor Activity In Lamprey, James F. Einum, James T. Buchanan

Biological Sciences Faculty Research and Publications

Reticulospinal neurons of the lamprey brain stem receive rhythmic input from the spinal cord during locomotor activity. The goal of the present study was to determine whether such spinal input has a direct component to reticulospinal neurons or depends on brain stem interneurons. To answer this question, an in vitro lamprey brain stem-spinal cord preparation was used with a diffusion barrier placed caudal to the obex, separating the experimental chamber into two baths. Locomotor activity was induced in the spinal cord by perfusion of D-glutamate or N-methyl-DL-aspartate into the spinal cord bath. The brain stem bath was first perfused …

Cholinergic Modulation Of The Locomotor Network In The Lamprey Spinal Cord, Katharina A. Quinlan, Peter G. Placas, James T. Buchanan

Biological Sciences Faculty Research and Publications

Acetylcholine (ACh) was found here to be a strong modulator of swimming activity in the isolated spinal cord preparation of the adult lamprey (Ichthyomyzon unicuspis). During fictive swimming induced with either D-glutamate or N-methyl-D-aspartate, addition of ACh (200 µM) significantly reduced the cycle period of ventral root bursts to 54%, intersegmental phase lag to 32%, and ventral root burst proportion to 80% of control levels. Effects of ACh were apparent at concentrations as low as 1 µM. Both nicotinic and muscarinic receptors are involved, in that application of either nicotinic or muscarinic agonists alone significantly reduced cycle …

Sinusoidal Length Oscillation- And Receptor-Mediated Mrna Expression Of Myosin Isoforms And Α-Sm Actin In Airway Smooth Muscle, Melissa Wahl, Thomas J. Eddinger, Chi-Ming Hai

Biological Sciences Faculty Research and Publications

We tested the hypothesis that sinusoidal length oscillation and receptor activation interactively regulate the abundance of mRNA encoding α-smooth muscle (α-SM) actin and myosin isoforms in intact bovine tracheal smooth muscle. We found that sinusoidal length oscillation significantly downregulated abundance of mRNA encoding α-SM actin mRNA in unstimulated tissues but not in histamine- and carbachol-activated tissues. This observation suggests antagonistic interactions between mechanical stretch and receptor-mediated signal transduction in regulating the abundance of mRNA encoding α-SM actin in intact airway smooth muscle. This pattern of antagonistic interaction was also observed in cholinergic receptor activation experiments. Whereas carbachol significantly upregulated myosin …

Cold Induction Of Earli1, A Putative Arabidopsis Lipid Transfer Protein, Is Light And Calcium Dependent, Jason A. Bubier, Michael Schläppi

Biological Sciences Faculty Research and Publications

As sessile organisms, plants must adapt to their environment. One approach toward understanding this adaptation is to investigate environmental regulation of gene expression. Our focus is on the environmental regulation of EARLI1, which is activated by cold and long-day photoperiods. Cold activation of EARLI1 in short-day photoperiods is slow, requiring several hours at 4ºC to detect an increase in mRNA abundance. EARLI1 is not efficiently cold-activated in etiolated seedlings, suggesting that photomorphogenesis is necessary for its cold activation. Cold activation of EARLI1 is inhibited in the presence of the calcium channel blocker lanthanum chloride or the calcium chelator EGTA. Addition …

The N-Terminal Prodomain Of Sv23 Is Essential For The Assembly Of A Functional Vitelline Membrane Network In Drosophila, Anita L. Manogaran, Gail L. Waring

Biological Sciences Faculty Research and Publications

The vitelline membrane is a specialized extracellular matrix that surrounds and protects the oocyte. Recent studies indicate that it also serves as a storage site for embryonic pattern determinants. sV23, a major vitelline membrane protein, is essential for the morphogenesis of the vitelline membrane as sV23 protein null mutants lay flaccid, infertile eggs. By analyzing a series of sV23 mutant transgenes in the sV23 protein null genetic background, we have shown that sV23 is secreted as a proprotein in functional excess and that C- and N-terminal prodomains are removed successively, following its deposition in the extracellular space. Although a target …

Homing Endonucleases Encoded By Germ Line-Limited Genes In Tetrahymena Thermophila Have Apetela2 Dna Binding Domains, Jeffrey D. Wuitschick, Paul R. Lindstrom, Alison E. Meyer, Kathleen M. Karrer

Biological Sciences Faculty Research and Publications

Three insertion elements were previously found in a family of germ line-limited mobile elements, the Tlr elements, in the ciliate Tetrahymena. Each of the insertions contains an open reading frame (ORF). Sequence analysis of the deduced proteins encoded by the elements suggests that they are homing endonucleases. The genes are designated TIE1-1, TIE2-1, and TIE3-1 for Tetrahymena insertion-homing endonuclease. The endonuclease motif occupies the amino terminal half of each TIE protein. The C-terminal regions of the proteins are similar to the APETELA2 DNA binding domain of plant transcription factors. The TIE1 and TIE3 elements belong to families of repeated sequences …

Passive Stretch Inhibits Central Corelike Lesion Formation In The Soleus Muscles Of Hindlimb-Suspended Unloaded Rats, D. V. Baewer, Mark A. Hoffman, Janell Romatowski, J. L. W. Bain, Robert H. Fitts, Danny A. Riley

Biological Sciences Faculty Research and Publications

Hindlimb suspension unloading (HSU) is a ground-based model simulating the effects of microgravity unloading on the musculoskeletal system. In this model, gravity causes the hind foot of the rat to drop, opening the front of the ankle to 90–105° plantar flexion at rest. As HSU proceeds, the normal weight-bearing angle of 30° dorsiflexion is achieved progressively less, and the contraction range of soleus is abbreviated. Our laboratory reported that 12 days of HSU caused central corelike lesions (CCLs) of myofibril breakdown (Riley DA, Slocum GR, Bain JL, Sedlak FR, Sowa TE, and Mellender JW. J Appl Physiol. 69: 58–66, 1990). …

Fiber Type And Temperature Dependence Of Inorganic Phosphate: Implications For Fatigue, Edward Patrick Debold, H. Dave, Robert H. Fitts

Biological Sciences Faculty Research and Publications

Elevated levels of P_i are thought to cause a substantial proportion of the loss in muscular force and power output during fatigue from intense contractile activity. However, support for this hypothesis is based, in part, on data from skinned single fibers obtained at low temperatures (≤15°C). The effect of high (30 mM) P_i concentration on the contractile function of chemically skinned single fibers was examined at both low (15°C) and high (30°C) temperatures using fibers isolated from rat soleus (type I fibers) and gastrocnemius (type II fibers) muscles. Elevating P_i from 0 to 30 mM at saturating …

2-O-Methylation Of Fucosyl Residues Of A Rhizobial Lipopolysaccharide Is Increased In Response To Host Exudate And Is Eliminated In A Symbiotically Defective Mutant, K. Dale Noel, Jodie M. Box, Valerie J. Boone

Biological Sciences Faculty Research and Publications

When Rhizobium etli CE3 was grown in the presence of Phaseolus vulgaris seed extracts containing anthocyanins, its lipopolysaccharide (LPS) sugar composition was changed in two ways: greatly decreased content of what is normally the terminal residue of the LPS, di-O-methylfucose, and a doubling of the 2-O-methylation of other fucose residues in the LPS O antigen. R. etli strain CE395 was isolated after Tn5 mutagenesis of strain CE3 by screening for mutant colonies that did not change antigenically in the presence of seed extract. The LPS of this strain completely lacked 2-O-methylfucose, regardless of whether anthocyanins …

Flagellar Radial Spoke Protein 2 Is A Calmodulin Binding Protein Required For Motility In Chlamydomonas Reinhardtii, Pinfen Yang, Chun Yang, Winfield S. Sale

Biological Sciences Faculty Research and Publications

Genetic and morphological studies have revealed that the radial spokes regulate ciliary and flagellar bending. Functional and biochemical analysis and the discovery of calmodulin in the radial spokes suggest that the regulatory mechanism involves control of axonemal protein phosphorylation and calcium binding to spoke proteins. To identify potential regulatory proteins in the radial spoke, in-gel kinase assays were performed on isolated axonemes and radial spoke fractions. The results indicated that radial spoke protein 2 (RSP2) can bind ATP and transfer phosphate in vitro. RSP2 was cloned and mapped to the PF24 locus, a gene required for motility. Sequencing revealed that …

Science On The Rise In Developing Countries, Milena Holmgren, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

No abstract provided.

Comparison Of Harvested And Nonharvested Painted Turtle Populations, Tony Gamble, Andrew M. Simons

Biological Sciences Faculty Research and Publications

Painted turtles (Chrysemys picta) are commercially harvested in large numbers in Minnesota for sale to biological supply companies and the pet trade. We investigated the possible effects of this harvest by comparing size, demography, and catch rates of painted turtles in 12 harvested and 10 nonharvested painted turtle populations in 2001 and 2002. We correlated turtle catch rates to harvest status, and harvested lakes had a lower catch-per-unit-effort than nonharvested lakes. Harvest had minimal effect on the size of turtles captured, and we found no significant differences in the count of male:female:juvenile turtles among lakes of different harvest …

Liana Diversity, Abundance, And Mortality In A Tropical Wet Forest In Costa Rica, Joseph Mascaro, Stefan A. Schnitzer, Walter P. Carson

Biological Sciences Faculty Research and Publications

Lianas can have a large impact on the diversity, structure, and dynamics of tropical forests, yet they remain essentially unknown even in some of the most intensely studied tropical forests, such as La Selva Biological Station in Costa Rica. We quantified the diversity, abundance, and mortality of lianas in primary and selectively logged forest at La Selva for over 3 years, from January 1999 until July 2002. We measured, identified, permanently marked, and mapped all lianas ≥1.3 m in length and 2 mm in diameter, whether climbing or free-standing, in nine, m (864 m²) plots. There were no …

Evolutionary Divergence In Developmental Strategies And Neuromodulatory Control Systems Of Two Amphibian Locomotor Networks, Simon D. Merrywest, David L. Mclean, James T. Buchanan, Keith T. Sillar

Biological Sciences Faculty Research and Publications

Attempts to understand the neural mechanisms which produce behaviour must consider both prevailing sensory cues and the central cellular and synaptic changes they direct. At each level, neuromodulation can additionally shape the final output. We have investigated neuromodulation in the developing spinal motor networks in hatchling tadpoles of two closely related amphibians, Xenopus laevis and Rana temporaria to examine the subtle differences in their behaviours that could be attributed to their evolutionary divergence.

At the point of hatching, both species can swim in response to a mechanosensory stimulus, however Rana embryos often display a more forceful, non-locomotory coiling behaviour. Whilst …

Nuclear Surveillance And Degradation Of Hypomodified Initiator TrnaMet In S. Cerevisiae, Sujatha Kadaba, Anna Krueger, Tamyra Trice, Annette M. Krecic, Alan G. Hinnebusch, James T. Anderson

Biological Sciences Faculty Research and Publications

The tRNA m¹A58 methyltransferase is composed of two subunits encoded by the essential genes TRM6 and TRM61 (formerly GCD10 and GCD14). The trm6-504 mutation results in a defective m¹A methyltransferase (Mtase) and a temperature-sensitive growth phenotype that is attributable to the absence of m¹A58 and consequential tRNA_i^Met instability. We used a genetic approach to identify the genes responsible for tRNA_i^Met degradation in trm6 cells. Three recessive extragenic mutations that suppress trm6-504 mutant phenotypes and restore hypomodified tRNA_i^Met to near normal levels were identified. The wild-type allele of …

The Radial Spokes And Central Apparatus: Mechano-Chemical Transducers That Regulate Flagellar Motility, Elizabeth F. Smith, Pinfen Yang

Biological Sciences Faculty Research and Publications

No abstract provided.

Establishment Limitation Reduces Species Recruitment And Species Richness As Soil Resources Rise, M. Henry, H. Stevens, Stefan A. Schnitzer, Walter P. Carson

Biological Sciences Faculty Research and Publications

1. At local spatial scales, species richness tends to fall as productivity rises. Most explanations have focused on increased extinction, but, instead, we test experimentally whether increased soil fertility reduces recruitment. Specifically, we test whether variation in recruitment is due to source limitation, germination limitation or establishment limitation, and how litter accumulation and seed predation contribute to these processes.
2. We established four crossed experimental treatments in a perennial‐dominated early successional plant community over 3 years. We added seed of 30 species, manipulated access by selected seed predators, removed litter and added slow release fertilizer at four levels (0, 8, 16 and …

Recruitment Of Lianas Into Logging Gaps And The Effects Of Pre-Harvest Climber Cutting In A Lowland Forest In Cameroon, Stefan A. Schnitzer, Marc P.E. Parren, Frans Bongers

Biological Sciences Faculty Research and Publications

The abundance of lianas (woody vines) and the detrimental impact that they have on tropical rain forest trees is widely recognized. Lianas are particularly abundant in disturbed areas of the forest, such as logging gaps, and pre-harvest liana cutting has been widely recommended throughout the tropics to reduce the impact of lianas during and following tree harvest. The effectiveness of forest-wide liana cutting, however, is currently unresolved, particularly for reducing liana abundance in logging gaps. Furthermore, our understanding of the dynamics and rate of liana colonization in gaps is limited. We tested: (1) the speed at which lianas recruit into …

Community Ecology And Management Of Lianas, Diego R. Perez-Salicrup, Stefan A. Schnitzer, Francis E. Putz

Biological Sciences Faculty Research and Publications

No abstract provided.

Yeast Oxa1 Interacts With Mitochondrial Ribosomes: The Importance Of The C‐Terminal Region Of Oxa1, Lixia Jia, Mary Kathryn Dienhart, Mark Schramp, Matthew Mccauley, Kai Hell, Rosemary A. Stuart

Biological Sciences Faculty Research and Publications

The yeast mitochondrial Oxa1 protein is a member of the conserved Oxa1/YidC/Alb3 protein family involved in the membrane insertion of proteins. Oxa1 mediates the insertion of proteins (nuclearly and mitochondrially encoded) into the inner membrane. The mitochondrially encoded substrates interact directly with Oxa1 during their synthesis as nascent chains and in a manner that is supported by the associated ribosome. We have investigated if the Oxa1 complex interacts with the mitochondrial ribosome. Evidence to support a physical association between Oxa1 and the large ribosomal subunit is presented. Our data indicate that the matrix‐exposed C‐terminal region of Oxa1 plays an important …

Genetic Locus And Structural Characterization Of The Biochemical Defect In The O-Antigenic Polysaccharide Of The Symbiotically Deficient Rhizobium Etli Mutant, Ce166, Lennart Scott Forsberg, K. Dale Noel, Jodie M. Box, Russell W. Carlson

Biological Sciences Faculty Research and Publications

The O-antigen polysaccharide (OPS) of Rhizobium etli CE3 lipopolysaccharide (LPS) is linked to the core oligosaccharide via an N-acetylquinovosaminosyl (QuiNAc) residue. A mutant of CE3, CE166, produces LPS with reduced amounts of OPS, and a suppressed mutant, CE166α, produces LPS with nearly normal OPS levels. Both mutants are deficient in QuiNAc production. Characterization of OPS from CE166 and CE166α showed that QuiNAc was replaced by its 4-keto derivative, 2-acetamido-2,6-dideoxyhexosyl-4-ulose. The identity of this residue was determined by NMR and mass spectrometry, and by gas chromatography-mass spectrometry analysis of its 2-acetamido-4-deutero-2,6-dideoxyhexosyl derivatives produced by reduction of the 4-keto group using …