Questions 2006-07

Faculty available to chair comps committees: Hougen-Eitzman, Jaramillo, McKone, Rand, Tymoczko, Walser-Kuntz, and Zweifel

1. (Walser-Kuntz) The innate immune system has evolved to recognize molecular patterns associated with various pathogens. One class of pattern recognition receptors is the toll-like receptor family. These receptors function by binding to conserved microbial components and signaling inflammatory and immune responses. Review what is known of the evolution, function, and/or signaling of the toll-like receptor family.

Dunne, A., and L. O’Neill. 2005. Adaptor usage and toll-like receptor signaling specificity. FEBS Letters 579: 3330-3335.

Shizuo, A. S., Uematsu, and O. Takeuchi. 2006. Pathogen recognition and innate immunity. Cell 124: 783-801.

2. (Tymoczko) Metabolic syndrome (Syndrome X, Insulin resistance syndrome) may be the most common metabolic disorder in the world. Metabolic syndrome is characterized by obesity, dysregulation of lipid metabolism, and insulin resistance. Clinical manifestations of the disorder include hypertension, cardiovascular disease, type 2 diabetes, polycystic ovarian syndrome, fatty liver disease, certain forms of cancer and sleep apnea. Explore the biochemical parameters that may be responsible for this syndrome with its wide array of symptoms.

Hegele, R. A. and R. L. Pollex. 2005. Genetic and physiological insights into the metabolic syndrome. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 289: R663-669.

McMillen, C.I. and J. S. Robinson. 2005. Developmental origins of the metabolic syndrome: prediction, plasticity and programming. Physiological Reviews 85: 571-633.

Reaven, G.M. 2005. Why syndrome X? From Harold Himsworth to the insulin resistance syndrome: an historical perspective. Cell Metabolism 1:9-14.

3. (McKone) Ecologists traditionally have emphasized the role of interspecific competition and predation in structuring communities. However, there has been increased recent interest in interspecific interactions in which at least one partner is benefited. Review the origins, stability, and ecological importance of mutualism and facilitation in natural communities.

Althoff, D. M., K. A. Segraves, and O. Pellmyr. 2005. Community context of an obligate mutualism: pollinator and florivore effects on Yucca filamentosa. Ecology 86:905-913.

Bruno, J. F., J. J. Stachowicz, and M. D. Bertness. 2003. Inclusion of facilitation into ecological theory. Trends in Ecology and Evolution 18:119-125.

Edwards, D. P., M. Hassall, W. J. Sutherland, and D. W. Yu. 2006. Selection for protection in an ant-plant mutualism: host sanctions, host modularity, and the principle-agent game. Proceedings of the Royal Society of London B 273:595-602.

Kummel, M., and S. W. Salant. 2006. The economics of mutualisms: optimal utilization of mycorrhizal mutualistic partners by plants. Ecology 87:892-902.

4. (McKone) Evolutionary biologists have been fascinated by differences between the sexes since Darwin marveled at the perfection of peacock feathers and wondered about their evolutionary origin. Though there is considerable evidence that some secondary sexual characteristics are used in mate choice, the information content of these “ornaments” has not been clear. Recent research has begun to unravel the mystery. Discuss the nature of the information to potential mates carried in secondary sexual characteristics, and how this information has influenced the evolution of sexual dimorphism.

Malo, A. F., E. R. S. Roldan, J. Garde, A. J. Soler, and M. Gomendio. 2005. Antlers honestly advertise sperm production and quality. Proceedings of the Royal Society of London B 272:149-157.

Mank, J. E., D. W. Hall, M. Kirkpatrick, and J. C. Avise. 2006. Sex chromosomes and male ornaments: a comparative evaluation in ray-finned fishes. Proceedings of the Royal Society of London B 273:233-236.

Morales, J., J. J. Sanz, and J. Moreno. 2006. Egg colour reflects the amount of yolk maternal antibodies and fledging success in a songbird. Biology Letters DOI: 10.1098/rsbl.2006.0471.

5. (Zweifel) Understanding the mechanism of transcriptional control is essential if we are to unravel the mystery of differentiation and maintenance of specific cell types. Chromatin not only allows for the compact storage of the genome, but it also serves as the substrate for transcription. Because chromatin has a strong inhibitory effect on nuclear processes that are dependent on protein-DNA interactions, eukaryotic cells have evolved many mechanisms to counteract, modify or take advantage of this negative effect.
Examine the current mechanisms of chromatin regulation and their role in transcriptional control.

Nightingale, K. P., O’Neill, L. P., and Turner, B. M. 2006. Histone modifications: signaling receptors and potential elements of heritable epigenetic change. Current Opinions in Genetics and Development 16:125-136. (The entire April 2006 issue is devoted to chromatin function)

6. (Hougen-Eitzman) Avoiding predation is a challenge that all organisms must accomplish if they are to reproduce. Many species use signals to avoid predations – these signals can involve some type of mimicry (such as Batesian and Müllerian mimicry), as well as a warning signal (such as aposematic coloration). Even though these types of signals are commonly studied, it is often unclear both how they might have evolved and their exact ecological function. Examine the evolution or ecological basis of a signal that helps the user avoid predation.

Beatty, C. C., K. Beriinckx, and T. N. Sherratt. 2004. The evolution of mullerian mimicry in multispecies communities. Nature 431:63-67.

Darst, C. R. and M. E. Cummings. 2006. Predator learning favours mimicry of a less-toxic model in poison frogs. Nature 440:208-211.

Mappes, J., N. Marples, and J. A. Endler. 2005. The complex business of survival by aposematism. Trends in Ecology and Evolution 20:598-603

7. (Rand) In multicellular organisms, close-range cell signaling systems that occur within specific tissues or organs and operate independent of the circulatory system are called paracrine systems. Often times paracrine-signaling operates as a local regulatory pathway of a larger secretory system. Not surprisingly, these paracrine relationships are common in immunological and neuroendocrine systems. Examples include, sympathetic regulation of glucocorticoid secretion, nitric oxide modulation of synaptic function, pancreatic b-cell inhibition of a-cell secretion, renal blood flow regulation through the juxtaglomerular apparatus, and possibly follicular dominance within the ovary. These systems have been difficult to study, in some cases due to the need to maintain anatomical integrity. However, a variety of new techniques have allowed investigators to gain access to the workings of a few of these paracrine systems. Choose a paracrine system where new insights have been gained in recent years. Describe the mechanistic details of the specific secretory interactions and the techniques used to elucidate these interactions.

Ishihara, H., P. Maechler. A. Gjinovci, P. Herrera, and C. B. Wollheim. 2003. Islet b-cell secretion determines glucagon release from neighboring a-cells. Nature Cell Biology 5:330-335.

8. (Jaramillo) Recent advances in the identification of molecular elements of the mechanoelectrical transduction process in hair cells have considerably altered our understanding of this process. Review current views of transduction and identify outstanding issues yet to be resolved.

Corey, D. et al. 2004. TRPA1 is a candidate for the mechanosensitive transduction channel of vertebrate hair cells. Nature 432, 723-730.

Siemens, J. et al. 2004. Cadherin 23 is a component of the tip link in hair-cell stereocilia. Nature 428, 950-955.

9. (Jaramillo) A recent review by D. M. Engelman says: Singer and Nicholson proposed the “fluid mosaic” model of membrane organization more than 30 years ago, and this is the model often seen in textbooks. New findings are undermining this view. Briefly review the mosaic model, identify and review recent developments which are significantly re-shaping our understanding of membrane structure/function.

Engelman, D. M. 2005. Membranes are more mosaic than fluid. Nature 438, 578-580 (and subsequent reviews).

10. (Hougen-Eitzman, McKone; student-submitted question) Plankton communities are major constituents in the nutrient cycling of saltwater ecosystems, and generally comprise the lowest trophic levels of marine food webs. Therefore, any changes in plankton abundance can have major repercussions for the entire ecosystem. Evaluate natural and/or anthropogenic factors that affect estuarine or marine plankton communities.

de Baar, H.J.W; et al. 2005. Synthesis of iron fertilization experiments. Journal of Geophysical Research 110: C09S16.

Edwards, M., and A.J. Richardson. 2004. Impact of climate change on marine pelagic phenology and trophic mismatch. Nature 430: 881-884.

Paerl, H.W, L.M. Valdes, B.L. Peierls, J.E. Adolf, and L.W. Harding. 2006. Anthropogenic and climatic influences on the eutrophication of large estuarine ecosystems. Limnology and Oceanography 51:448-462.