Faculty Research Interests
Students are encouraged to do research with a faculty member during their undergraduate experience at PLU.
Check the Natural Sciences website for more information about the Undergraduate Research summer program.
I am a microbial ecologist interested in studying microbial communities in natural environments with the goals of understanding how the microbes are contributing to global processes and what products these microbes may be making that may be of biotechnological significance. Currently, I am examining microbial communities in forest canopy soils of the Pacific Northwest.
My long-term goal is to document the microbial diversity in forest canopy soils, and to place them in the context of the forest ecosystem as a whole, by directly comparing canopy soils to those on the forest floor. Because only 1% or less of Earth’s bacteria has been successfully cultured in the laboratory, I use culture-independent techniques, including many molecular tools, to assess the diversity of this virtually unknown and potentially significant environmental niche.
My research interests include ecology and biogeography, primarily in aquatic systems. Much of my past research has focused on interactions between herbivores and algae in marine systems. This has included studies of geographical gradients of herbivorous fish diversity and how temperature effects on physiology may play a role in driving this pattern and the effects of fisheries and disease on sea urchins and kelp forest ecology.
My current research projects include studies of the community ecology of rocky shores of Puget Sound, disease ecology of sea urchins, and larval ecology of bivalves. These projects involve undergraduate student researchers at PLU and collaborators from the University of Washington and Harbor WildWatch.
My research with the oriental fire-bellied toad, Bombina orientalis, addresses cellular and molecular aspects of embryonic development, larval development, and metamorphosis.
Work I have done with students includes the following:
- We have demonstrated that relatively high levels of a common environmental contaminant, bis-phenol A (BPA) disrupt gastrulation. Protein expression, as assessed by polyacrylamide gel electrophoresis, differs between treated and control animals. We would like to determine the relationship between these differences and gastrulation defects.
- BPA is both a thyrogenic agent and an estrogenic agent; thus BPA can be considered an endocrine disruptor. Changes accompanying tadpole metamorphosis (e.g., regression of the tail) are evoked by thyroid hormones, and these changes are affected by BPA. We are also doing long-term experiments in which we expose tadpoles to environmental levels of BPA throughout larval development to determine if the estrogenic action of BPA promotes expression of the female phenotype (e.g., presence of ovaries) in animals that genetically are males.
- We have demonstrated that both regression of the tail and remodeling of the digestive system during metamorphosis involve programmed cell death, or apoptosis. Regression of the tail is accompanied by typical features of apoptosis – internucleosomal degradation of chromatin and degradation of proteins by caspases. We also have evidence that other protein degrading enzymes – cathepsins – contribute to tail regression. We would like to determine the how apoptosis is related to both cathepsin activation and lysosome contribution to tissue degradation that contributes to tail regression.
- Even though limb regeneration occurs in adult salamanders, this phenomenon is not displayed by any adult frog. Limb regeneration does occur in Bombina orientalis larvae. We would like to determine the window available for normal regeneration. We already know that limbs amputated near the end of larval development do not regenerate. We would like to determine if prolonging larval development will allow limb regeneration. We will amputate limbs near the end of larval development, then indefinitely prevent metamorphosis by culturing tadpoles in the presence of 6-n-propyl 2-thiouracil, which blocks the action of thyroid hormones; this will allow us to determine if the ability to regenerate is irreversibly lost at a certain larval stage, or if failure to regenerate is more directly related to the time available before onset of metamorphic climax.
- Most of the studies noted above relate to protein expression, which we have assessed using assays of various sorts and polyacrylamide gel electrophoresis. In each case a more sophisticated proteome analysis could be conducted by pairing two-dimensional gel electrophoresis with mass spectrometry.
As an evolutionary biologist and systematist, my primary research interests involve using the tools of phylogenetic systematics to help answer questions about speciation, phylogeography, relationships among species, and morphological evolution. I am an ichthyologist by training and I work primarily with North American freshwater fishes. My research involves field collection of specimens, DNA sequencing, and specimen-based morphological work.
My past research projects have involved using morphological and molecular data to reconstruct evolutionary relationships, cryptic diversity, and spine morphology in madtom catfishes. I am currently working on the phylogeography of fishes distributed in the Mississippi Embayment, a region containing multiple lowland streams in western Tennessee and Mississippi. The goal of this project is to understand how past events in earth history (i.e. glacial cycles and fluctuating sea levels) have affected the distribution of species in this region.
Rosemarie (Romey) Haberle
My research uses both phylogenetic and comparative chloroplast genomic approaches to better understand the evolutionary biology of flowering plants. Currently, I am studying members of the bluebell family (Campanulaceae) which is an excellent model system to address different evolutionary biology questions. I use both molecular and nonmolecular approaches to develop hypotheses regarding their taxonomic and biogeographic relationships.
Additionally, I am using bioinformatic tools to examine the unusual structural rearrangements found in chloroplast genomes of the bluebells and their close relatives. Complementary to my current research interests, I am interested in the ecology and genetics of rare and invasive plant species of the Pacific Northwest, and in contributing to knowledge of the botanical biodiversity of the region through field and floristic studies. I welcome undergraduate researchers to join me in lab, field, or herbarium focused projects.
My research stems from my interest in the ability of plants to respond to environmental stimuli and to initiate intracellular signaling cascades. Calcium is a key signal transducing molecule in plants. I work on genes that encode Calcium Dependent Protein Kinases, unique calcium sensing molecules that function within plant cells to phosphorylate other proteins in response to elevated intracellular calcium levels.
Many stimuli cause an increase in intracellular calcium levels in plant cells including, but not limited to, light, gravity, wounding and osmotic stress. Students in my lab have been involved in cloning members of the CDPK gene family in zucchini. The goal of isolating these genes and studying their expression is to explore the hypothesis that different members of the gene family are expressed in different tissues and in response to different stimuli. Students working on these projects have an opportunity to use techniques such as PCR, rtPCR, Northern blot analysis and DNA sequencing and analysis to address these questions.
My research is based on understanding how plants respond to infection. We focus on a plant defense hormone called jasmonic acid (JA). JA plays a major role in coordinating a plant’s response to insect herbivory, wounding, and many infections. But the signaling that occurs in the plant to mediate these responses is unclear. Experiments in my lab are aimed at identifying genes involved in the JA-responsive signaling pathway through mutational analysis.
By understanding how plants respond to infection, I hope to contribute to research that will lead to overall healthier crops and more productive, sustainable agriculture.
My research focuses on Staphylococcus aureus, a pathogen responsible for causing a wide range of infections. The ability of S. aureus to cause infections requires that at some level it is able to either subvert or alter the host immune response to infection. Work in my lab focuses on examining how the ability of S. aureus to scavenge iron from the host affects both the bacterial and host responses during infection.
My interest lies in determining how iron acquisition not only impacts the interaction of S. aureus with host cells, but how this mechanism could be exploited as a therapeutic strategy. With the ever-increasing emergence of antibiotic resistant strains of S. aureus, the identification of alternative treatment strategies remains a priority.
My research has examined the ecological and behavioral processes promoting speciation in North American Red Crossbills. My work has centered on a newly discovered population of crossbills in the South Hills, Idaho where in the absence of squirrels, crossbills and lodgepole pine have coevolved. This has resulted in divergent selection between crossbills in the South Hills and the Rocky Mountains.
My work shows that mate choice is highly assortative in the South Hills, indicating that reproductive isolation is evolving between these recently diverged populations (perhaps in only the last 3,000 years).
Several ecological and behavioral factors act to promote reproductive isolation. For example, Rocky Mountain crossbills (mostly call types 2 and 5) are rare in the South Hills when South Hills crossbills begin pairing in February, presumably because Rocky Mountain crossbills have relatively low feeding rates on the well-defended cones in the South Hills. Not until later in the spring and summer, when seed availability increases, do Rocky Mountain crossbills become common. Then, interbreeding can and does occasionally occur. This suggests that temporal isolation may reduce gene flow, but it is not the only reproductive barrier.
Ecology-based selection also favors assortative grouping in Red Crossbills and may promote reproductive isolation as a by-product. Public information use in which individuals estimate patch quality by using the success of group mates foraging in the same patch is important to Red Crossbills (Smith et al. 1999). Effective use of public information by foraging Red Crossbills depends on similarities in feeding abilities among flock mates, which in turn depends upon flock mates having similar bill structures. Thus, public information use should favor assortative flocking by trophic phenotype. My data suggests that public information use promotes assortative flocking and may have favored the divergence of flight calls among the visually similar Red Crossbills call types. Moreover, assortative flocking may promote reproductive isolation because mates are often (usually?) chosen from within flocks.
An additional behavioral factor that may promote assortative pairing is song divergence. I am currently investigating the nature and extent of song divergence between call types.
My research centers around the mechanisms by which estrogen exerts effects on the central nervous system that goes beyond its ability to merely drive reproductive function. Recent evidence suggests that estrogen plays a role in such diverse functions as learning and memory, growth and development, and fine motor skills. The pleiotropic effects of estrogen may, in part, be mediated by astrocytes since these supportive cells of the nervous system are direct targets for estrogen’s actions.
These predominant glial cells contain estrogen receptors and estrogen response elements have been found to be present in the promoter region of several glial-specific genes. The mapping of the entire genome of several species has enabled neuroscientists to simultaneously examine the expression levels of tens of thousands of mRNA transcripts in a single experiment. I am currently using the microarray analysis service provided by the Genome Consortium for Active Teaching (GCAT) to investigate the differential gene expression profile induced by estrogen in cultured astrocytes. It is hoped that results obtained from this study will provide a number of estrogen-responsive genes to further explore in the coming years with real-time polymerase chain reaction (PCR), Western blot and other experimental methodologies.