Research

ENVIRONMENTAL PHYSIOLOGY

Nancy Berner studies acclimation — a process by which organisms modify their phenotype to match their environment. In particular, Dr. Berner studies mechanisms controlling seasonal acclimation — reversible phenotypic changes brought on by changes in season — in the Eastern red spotted newt.

Overview: The Eastern red spotted newt, found in abundance in the Eastern US, is an amphibian that is active during the cold winter months. They don’t become dormant like other amphibians (e.g. frogs) and most reptiles (e.g. turtles). We investigate the physiological factors that allow these newts to continue to function in the cold. We have identified a suite of changes that occur between summer and winter newts. Winter newts have higher standard metabolic rates, have increased activity of certain enzymes, change membrane fatty acid composition toward more polyunsaturated fatty acids and prefer cooler temperatures in a gradient than summer newts. We think these changes gives them the option to be active in the cold.

Projects in the laboratory are now funded by the National Science Foundation (IOS-1120448), which includes funding for several undergraduate research fellows each summer. These studies focus on how the changes in enzyme activities and metabolic rate are brought about on the cellular and molecular levels.

Current projects include:

  • Environmental Trigger for Acclimation — Spring 2013 finds us with a third run of an experiment set up. This experiment is helping us to  determine if the main environmental trigger for getting the acclimation processes underway is the seasonal change in temperature, change in light cycle (shorter days) or both. Based on data collected so far, light may play a role. (Poster presented at the SICB annual meeting in January 2013).
  • Plasma Melatonin Sampling — Spring 2013 brings us a new experiment to begin. If light has an effect on acclimation - what is the mechanism for its action? We are sampling plasma from newts at different times of day and year to see if melatonin levels change. This is being done with collaborators at Penn State and Lock Haven Universities who can measure melatonin. These experiments are being spearheaded by April Shi, a junior in the college.
  • Cardiolipin Charactization continued — Two freshmen in the lab are continuing the cardiolipin (CL) work by Sara Roberson referenced below. CL is only found in the inner mitochondrial membrane, and it interacts with cytochrome c oxidase to modify its activity. We want to determine if the changes in membrane structure that appear to influence enzyme activity are due to changes in CL fatty acid content. We do the HPLC work in Sewanee, and the LC-MS/MS work at Vanderbilt University.
  • Gene Expression continued — There is a variety of genes that we want to investigate, so with our collaborators at Miami University of Ohio, we are going to get the newt transcriptome sequenced by Next Generation RNAseq. This will help junior Asia Macintosh by making the cloning of the genes easier, allowing her to move on with rt-PCR of our genes of interest.
  • Tadpole Acclimation — This project is being done by two juniors in the lab - Astrid Escobar and Kathryn Gray. We are working with collaborators at Miami University of Ohio, measuring enzyme activity, metabolic rate, escape behavior and membrand composition in summer and winter tadpoles.

Planned projects include:

  • Mechanism of Temperature Sensing — Newts are able to behaviorally thermoregulate, and do so differently depending upon season. These experiments will investigate the expression of recently discovered temperature sensing molecules in newts.

Recent past projects include:

  • Cardiolipin Characterization — For her honors thesis, Sara Roberson (C’10, currently in graduate school at John's Hopkins University) investigated a particular membrane phospholipid called cardiolipin (CL). Data were presented as and abstract at the annual SICB meeting in January 2011.
  • Gene Expression — Trevor Marquand (C'13 - current biochemistry and classics double major) started this work in Fall 2010. Trevor compared the expression levels of key mitochondrial metabolic enzymes in summer and winter newts. These data are currently in press with the journal Trends in Comparative Biochemistry and Physiology.
  • Membrane Remodeling — Jack Bullock (C’11, currently in medical school in Florida), also for an honors thesis, investigated whether or not the bulk membrane fatty acid components change with season in skeletal muscle and liver tissue. These data are also in the paper in press with Trends in Comparative Biochemistry and Physiology.
  • Effect of Diet — We fed diets with different fatty acid contents to our newts, which in turn modified membrane composition and function, as well as standard metabolic rate and behavioral thermoregulation. These data are currently being written up for publication.