Asa Gray Biological Society Seminar Series
*Please note that our 25 March (Kirchman) and 22 April (Aaronson) presentations have switched dates relative to the dates originally printed in the UC Cultural Events Calendar.
February 4, 2013
Sean Robinson, Ph.D.
Lecturer, Department of Biology, Botany and General Biology, State University of New York-Oneonta
Title: Experimental and Molecular Studies of Bryophyte Dispersal on Alpine Summits
Abstract: In bryophytes, spores are considered to be the primary agents of long-distance dispersal, whereas asexual propagules, such as shoot fragments, are thought to have shorter dispersal distances. Many bryophytes, however, rarely or never produce spores, especially in environmentally harsh habitats such as alpine summits. A review of bryophyte dispersal studies over the last sixty years revealed that the role of gametophytic fragments in bryophyte population dynamics has not been adequately addressed. Sphagnum pylaesii reproduces primarily by fragmentation, yet it maintains large populations on several of the Adirondack alpine summits. The importance of vegetative fragments in the dispersal of this species was evaluated in parallel comparative studies of Sphagnum tenellum using direct and indirect methods. S. tenellum occupies similar habitats but differs in sexual condition and amount of spore production. To determine dispersal ability experimentally on alpine summits, branch fragments were coated with ultraviolet fluorescent dye and released from specific locations on two alpine summits. Distances traveled by fragments were measured after being located during evening surveys using ultraviolet LED light sources 24 h after initial release. These data fit a leptokurtic distribution, with a maximum dispersal distance of 54 m, the longest distance measured for wind dispersed bryophyte fragments. Dispersal ability of S. pylaesii fragments was assessed further by releasing fragments in a wind tunnel at varying wind speeds. These experiments support the field experiments, showing maximum fragment dispersal at wind speeds below mean wind speeds measured on the summit of Mt. Marcy. As an indirect measure of dispersal between the Adirondack summits, population differentiation (FST), and estimated gene flow (Nm) were calculated from genetic variation at fifteen microsatellite loci. Molecular data support the hypothesis that Sphagnum pylaesii has dispersed successfully among summits through fragmentation, given a lack of genetic variability (P = 0, A = 0), and consequently no differentiation (FST = 0) and high gene flow (Nm = ∞) between the summits.
February 18, 2013
Laura Prestia, Ph.D
PhD Candidate, Neuroscience Graduate Program, Department of Psychiatry, SUNY Upstate Medical University
Title: Molecular Mechanisms Underlying the Chemosensory-mediated Enhanced Acceptance of Ethanol as a Consequence of Prenatal Exposure
Abstract: Human and animal studies demonstrate multiple negative effects of prenatal ethanol exposure on postnatal development. Among these include the increased probability of postnatal ethanol preference that can lead to drug addiction. Previously, we demonstrated that prenatal exposure increased adolescent ethanol intake and this effect was mediated, in part, by enhanced olfactory behavior tuned to ethanol, and increased oral acceptability of ethanol’s specific aversive flavor attributes, bitter and oral irritation. Without further ethanol exposure, these behavioral alterations normalized by adulthood. We are currently investigating the underlying molecular basis for increased ethanol avidity and oral acceptability stemming from prior fetal ethanol exposure.
March 4, 2013
Steven Fletcher, Ph.D.
Assistant Professor, Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy
Title: Antagonism of the Oncogenic Bak–Bcl-xL and Bak–Mcl-1 Protein–Protein Interactions with Synthetic-Helix Mimetics
Abstract: Bcl-xL and Mcl-1 are anti-apoptotic proteins that are tightly regulated by pro-apoptotic proteins, which include Bak and Bim. The protein–protein interaction is mediated by an amphipathic -helix referred to as the BH3 “death” domain, which is located on the pro-apoptotic proteins and is engaged by a hydrophobic crevice on the anti-apototic proteins. We have designed synthetic mimetics of the hydrophobic face of the Bak-BH3 -helix and identified potent inhibitors of Bcl-xL and Mcl-1 in vitro (for example, JY-1-106: Kd = 196 nM (Bcl-xL), 10 M (Mcl-1)). Furthermore, our compounds disrupt the Bak–Mcl-1 interaction in cells, and, through freeing up of the pro-apoptotic proteins, induce intrinsic apoptosis of Bcl-xL and Mcl-1 overexpressing cancer cell lines. Preliminary animal studies indicate our lead compound JY-1-106 exhibits good anti-tumor activity. Mcl-1 has recently emerged as a “hot” anti-cancer target since its overexpression results in resistance to conventional chemotherapeutic drugs. Current work involves developing more potent and more selective Mcl-1 inhibitors through mimicry of both the polar and hydrophobic faces of the BH3 -helix, which will represent the first-ever functional, synthetic, amphipathic -helix mimetics.
March 25, 2013
Jeremy J. Kirchman, Ph.D.
Curator of Birds, New York State Museum
Title: Specimen-based Ornithology at the New York State Museum
Abstract: New York State Museum Curator of Birds Dr. Jeremy J. Kirchman will provide an overview of the NYSM ornithology collection, comprising nearly 20,000 specimens, and will highlight some of the ways the collection is used in his own research and by researchers and educators across the country. In the second half of the talk Kirchman will present preliminary analyses from an ongoing study he is conducting on the evolution of species ranges in the face of climate change. This example of specimen-based ornithology examines the range dynamics and morphological evolution of Red-bellied Woodpeckers over the last 150 years.
April 1, 2013
Terry D. Schwaner, Ph.D.
Dean, Center for Life and Health Sciences, Mohawk Valley Community College
Title: The Evolution of Body Size and Shape in Insular Tiger Snakes: Hypotheses and the Evidence
Abstract: Body size is an important life history trait whose evolution may be related to energy budgets for prey and prey handling, predation and/or competition, or socio-sexual factors. On offshore islands of southern Australia mean adult body sizes among populations of tiger snakes (Notechis scutatus/ater complex: Elapidae) exhibit a six-fold difference in length and weight. Molecular evidence supports a relatively recent change within the time of isolation of these continental islands (5000-8000 ybp). Predation does not seem to have been a factor in these changes, and conclusive evidence of socio-sexual interactions (i.e., male-male combat) perhaps cannot explain all cases, whereas prey differences among islands correlate well with average body sizes. Tests show that growth is both ecophenotypic and ecotypic, however the precise genetic mechanism is unknown. In this discussion, I will summarize the arguments and evidence gathered thus far and offer a new hypothesis with limited supporting data to explain how body sizes and shapes evolved in these snakes.
April 22, 2013
Lawrence R. Aaronson, Ph.D.
Professor of Microbiology, Biology Department, Utica College
Title: Slip Sliding Away and Getting a Tan: A Tale of Two Bacteria and How They Respond to Physical Changes in Their Environment
Abstract: Bacteria live in complex communities where chemical and physical factors and the microbial census can change rapidly. As a result, bacteria often need to adapt quickly to environmental change. Over the past several years, our lab group has been investigating how two different species of bacteria respond to biochemical and physical alterations in their environment. Bacillus cereus is a common soil-dwelling bacterium that may cause gastrointestinal disease when consumed in unpasteurized dairy products. When grown on solidified nutrient-rich media, these bacteria exhibit swarming, a type of high-energy motility facilitated by the hyperproduction of flagella. On media containing cow’s milk, however, B. cereus exhibits sliding motility, characterized by elaborate dendritic outgrowths from the central mass of the colony. Recent work in our laboratory has shown that the major milk protein casein alone can induce B. cereus sliding. Casein is a hydrophobic protein, so we hypothesized that other agents that alter the hydrophobicity or surface tension of the agar would have a similar effect. When grown on media containing the nonionic detergent NP-40, B. cereus also exhibited sliding. This suggests that the bacteria are sensing a physical change in their environment leading to a switch in their mode of motility. We have recently isolated a collection of mutants that do not slide on milk or NP-40, and are using molecular genetic techniques to clone and sequence the affected genes. The second microbe we study is a novel bacterium isolated by students in our lab, which we have named Pseudomonas uticensis. Among the interesting attributes of this bacterium is that it produces the brown pigment melanin. Studies in our lab revealed that melanin production is regulated by light; bacteria grown in the dark are unpigmented but turn brown within hours of exposure to white light. Exposure to increasing light intensity enhances melanin production, suggesting that the bacteria have a photosensory mechanism that regulates pigment production. Recently, we have also discovered that melanin production increases proportionately with increased cell density in culture. This suggests that quorum sensing signaling pathways also regulate melanin production in P. uticensis. We have isolated several mutant strains of the bacterium that are defective in melanogenesis, as well as one mutant strain that overproduces melanin, and are working to identify the genes involved in light- and quorum-regulation of melanin production in P. uticensis.
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