Date of Graduation

12-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Cell & Molecular Biology

Advisor/Mentor

Bottje, Walter G.

Committee Member

Dridi, Sami

Second Committee Member

Hargis, Billy M.

Third Committee Member

Kong, Byung-Whi

Fourth Committee Member

Baum, Jamie I.

Keywords

Biological sciences; Autophagy; Avian; Feed efficiency; Heat stress

Abstract

Autophagy is a highly conserved cellular mechanism that is responsible for the degradation and recycling of damaged organelles. Recently, autophagy has been involved in critical roles during overall development of the organism and degradation of damaged cellular components. This pathway has witnessed dramatic growth in the last few years and has been extensively studied in yeast and mammals, however, there is a paucity of information in avian (non-mammalian) species. First, we characterized genes involved in the autophagy pathway in male and female Jungle Fowl to determine gender and tissue specific differences. Secondly, tissue and genotype differences in Japanese quail selected for resistance (R) or susceptibility (S) to restraint stress was determined. Stress, whether external (temperature stress, disease, crowding) or internal (endogenous oxidative stress) reduces animal production efficiency. A major source of oxidative stress in cells is mitochondrial reactive oxygen species (ROS). Mitochondria are responsible for 90% of cellular energy (ATP) production and also a major site of ROS production. Oxidative damage of membranes induces lipid peroxidation with increased production of aldehydes and peroxides including 4-hydroxy-2-nonenal (4-HNE). Cells must expend energy to repair oxidative damage caused by 4-HNE protein adduct formation, possibly through utilization of the autophagy pathway. Lastly, as a result of the genetic selection of broiler (meat-type breeder) chickens for enhanced growth rate and lower feed conversion ratio, it has become necessary to restrict feed intake. When broilers are fed ad libitum, they would become obese and suffer from several health-related problems of which, autophagy may be a key regulator. In relation to this, feed efficiency (FE) is a very important genetic trait in poultry and livestock that can be negatively impacted by stress. Preliminary data from our laboratory indicates that autophagy expression of several genes is upregulated in muscle of broilers exhibiting a high FE phenotype compared to the low FE phenotype. This suggests that part of the cellular basis of FE may hinge on the ability of the cell to maintain optimal functionality by a more active endogenous repair system offered by the autophagy pathway.

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