Changes in Concentrations of Heat Shock Protein 60, 70 and 90 of a Wild Songbird in Responses to Distinct Stress Challenges
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Wild songbirds, such as the House Finch (Carpodacus mexicanus) require physiological mechanisms to maintain the homeostasis in face of stress threats. One of the primary mechanisms to protect system integrity is production of heat shock proteins (HSPs). Heat shock proteins belong to chaperone families that play key roles in supervising the folding structures of proteins, helping vertebrates to suppress and degrade denatured proteins in multiple stressful environments. HSP90, HSP70 and HSP60 are three major HSP families that have been used as biomarkers of stress in a wide range of vertebrates. In my thesis, I used heat shock protein concentrations of male House Finches to evaluate the responses of wild songbirds under multiple stressful environments: thermal stress, disturbance stress and pathogen stresses. My study is the first study to compare different HSPs responses of wild songbird under sequential and distinct stressful environments. HSP concentrations from blood samples of birds were measured by western blot assay and were adjusted by internal controls to counteract variations in western blotting efficiency. Male house finches were trapped a feeding stations in Arizona in hot and cool weather. Birds were then transported to aviary and kept in cages to experience sequential stresses. In chapter one, we evaluated the HSPs responses of wild male house finches in response to thermal stress. Through comparisons of the HSP concentrations in response to hot versus cool weather condition, we found that both HSP70 and HSP60 showed significantly increased concentrations in hot weather, while concentration of HSP90 did not change. The results demonstrated that HSP70 and HSP60 were sensitive in response to thermal stress and HSP70 can be a reliable indicator of thermal stress of male house finches in wild. I chapter two, male house finches were transported to Auburn, AL from Arizona by van. We then measured the HSP responses of birds under sequential and distinct stressful environments: hot weather, transportation, recovery period, and MG (Mycoplasma gallisepticum) pathogen infection. Results showed that all HSPs－HSP90, HSP70 and HSP60－had significantly different responses of changes in concentrations across those the four conditions. Although the responses of the three heat shock proteins varied, concentrations of all three HSPs were highest in MG-infection condition. MG infection was demonstrated to have the most significant effect on HSP responses. In addition, due to different concentration pattern of each HSP, studies of different stressors should choose different HSPs.