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Department of Biology University of St. Thomas, Minnesota USA

Summer 2006 Research
Inquiry at UST

 


Physiological Ecology of Reptiles--Tony Steyermark's lab

 

Mikkel Haugen, Alyson Lokken and Beth McGarry

Population status and movement patterns of an urban population of painted turtles in Minnesota

Abstract:
 The effects of commercial harvesting on the success and vitality of painted turtle (Chrysemys picta) populations are still widely unknown. A greater knowledge of population dynamics and intra-species relations and movement patterns will allow county officials and environmentalists to better understand and account for these effects. This investigation analyzes trends within a painted turtle population of a small, non-harvested lake in Shoreview, Minnesota. For three summers, we placed basking traps in twelve locations across the lake chosen for their variation in depth and proximity to land. Individuals were individually marked, and carapace length, plastron length, girth, and mass measurements were taken upon each capture. We estimated population size, sex ratio, and size class distribution, and then analyzed movement and distribution patterns using Geographic Information System (GIS). Preliminary results suggest correlations between gender and movement patterns, and between water depth and population density.

 

 

 

Hank Kemp

Cytochrome Oxidase, Uncoupling Protein 2, and among-individual variation in standard metabolic rate

Abstract:
Following the identification of uncoupling protein-2 (UCP2) as a mitochondrial carrier protein homologous to the original uncoupling protein UCP1 (thermogenin) and subsequent discovery that UCP2 was expressed ubiquitously, many studies have investigated the family of uncoupling proteins. In spite of all this interest, the physiological role of UCP2 is still unknown. Studies have claimed that upregulation of UCP2 results in decreased mitochondrial potential. Some have postulated from this that UCP2 may play a role in non-shivering thermogenesis similar to UCP1. If that is case, then one would expect to find a relationship between UCP2 and standard metabolic rate (SMR), a physiological quality linked closely to mitochondrial membrane potential. We investigated the relationship between relative UCP2 content and SMR in the common snapping turtle, Chelydra serpentina. Standard metabolic rate was determined by carbon dioxide consumption measured using an open-flow, push-through respirometry system. Following SMR determination, each turtle was sacrificed, its liver harvested, and liver mitochondrial protein was probed for UCP2 content using western blotting. Blots were analyzed to determine relative UCP2 content. Initial results indicate no significant relationship between relative UCP2 content and mass adjusted SMR. Pending further data collection and analysis, our results lend support to those that reject the idea that the function of UCP2 was thermogenic.

 

 

Plant Physiology--- Amy Verhoeven's lab

Mike Blissenbach

Analysis of Protein Changes Associated With Photosynthetic Recovery in Winter Stressed Conifers.

Abstract:
Plants that keep their leaves during winter (evergreens) are subject to low temperatures that reduce their ability to do photosynthesis, but these plants are still exposed to high light levels. This results in an imbalance between light absorption and its utilization via photosynthesis. Evergreens deal with this excess light energy by retaining constantly high levels of the photoprotective xanthophyll cycle pigments zeaxanthin and antheraxanthin in their leaves during winter. There is evidence that seasonal changes in photosynthetic proteins accompany these changes in photoprotective pigments. The  purpose of this study was to experimentally manipulate winter stressed leaves by removing branches from evergreens during January and maintaining them in the laboratory for one week.  Our goal was to monitor changes in photosynthetic proteins that accompany the recovery in photosynthetic activity and the xanthophyll cycle.

Branches from sun and shade samples of balsam fir (Abies balsamea), and sun samples of eastern white pine (Pinus strobus), were initially monitored in the field on a cold January morning.  Branches were collected and brought into the laboratory where they were allowed to recover for one week.  Photosynthetic parameters were monitored throughout recovery. Additionally, thylakoids were isolated periodically during recovery and frozen in liquid nitrogen.   Changes in specific light harvesting proteins were analyzed via gel electrophoresis and western blotting of the proteins contained in the thylakoid fractions.  The results of this study showed that both species recovered their photosynthetic activity consistently over the course of the week.   Additionally, both species displayed increases in the concentrations in nearly all of the light harvesting proteins as the branches recovered. However, one of these proteins, Lhcb2, showed decreases in concentrations as the branches recovered. These results are interesting because they demonstrate that different light harvesting proteins may have different specializations of function, with Lhcb2 perhaps being associated with photoprotection.

 

Angela Osmolak  & Jordan Crow

Seasonal changes in relative abundance and phosphorylation status of light harvesting and reaction center proteins in Pinus strobus and Abies balsamea.

Abstract:
In evergreens exposed to seasonally cold environments, there is strong evidence that the light harvesting complexes of photosystem II functionally change from energy harvesting to energy dissipating centers.  Here we report data from a study examining seasonal changes in relative abundance and phosphorylation status of light harvesting and reaction center proteins in the evergreens Pinus strobus (growing in the sun) and Abies balsamea (growing in sun and shade environments) in the seasonally very cold climate of Saint Paul, Minnesota.  Thylakoids were isolated every two months from January 2005 until January 2006 and western analysis of thylakoid fractions using antibodies to specific light harvesting and reaction center proteins were performed.  Antibodies were used to quantify the concentration of the different proteins during each season. Additionally, using the anti-phosphothreonine antibody, protein phosphorylation status was assessed to determine which proteins of PSII showed changes in phosphorylation status under different light and temperature conditions.  Results indicate that the majority of the light harvesting complex proteins (Lhcs) decrease in relative abundance during winter (b1, b4, b5, a1, and a4) in sun plants.  Interestingly, one of the light harvesting proteins (Lhcb2) does not decrease during winter, and another shows a much smaller decrease (PsbS).  Shade plants showed much less seasonal change in protein abundance.  Seasonal changes in the phosphorylation pattern of the photosynthetic proteins showed interesting differences in sun and shade needles, and also suggest an increased phosphorylation, during winter, of the low molecular weight PsbH protein. The results are discussed in the context of specific changes in the composition of the light harvesting apparatus as a component of the reconfiguration of the photosynthetic apparatus from light harvesting to dissipating centers during winter.