Molecular Mechanisms of Dietary Modulation of Intestinal Enzymes in Birds

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Many birds and mammals are omnivorous, eating a wide variety of foods depending on changing availability or nutritional requirements, and the production of digestive enzymes may increase with availability of substrate in the diet. This mode of regulation maximizes the digestibility of substrates when they are at high dietary levels and minimizes the cost of synthesizing excess enzyme when the substrate is at low levels. Building on past NSF-supported research, the PI will test hypotheses about the molecular regulatory basis of intestinal enzymatic flexibility. Research on digestive enzyme regulation in birds will either strengthen what may be an emerging generality (if in agreement with rodent studies) or transform current thinking about regulation of digestive enzymes. The enhanced understanding will also improve predictions about birds' abilities to respond to changes in diet that occur due to habitat alterations or climate change.Project I focuses on house sparrow (Passer domesticus) juveniles, which do exhibit intestinal carboydrase flexibility, and adults, which do not. The goal is to identify key molecular players and their rates of change in dietary modulation of intestinal carbohydrases and aminopeptidase-N in the juveniles, and test whether the carbohydrase expression regulatory machinery is silenced in the adults switched between diets. Project II focuses on comparison of wild omnivorous representatives from passerine, nonpasserine, and rodent clades. The goal is to test for differences in underlying gene expression regulatory mechanisms and their rates of change. Using tissues harvested from animals fed contrasting diets, the PI will test for molecular mechanisms underlying enzymatic patterns of response and the time-course for regulatory responses. The research supports international collaboration and also training at postdoctoral, graduate, undergraduates and high school levels. Data from these studies will be shared at national and international scientific conferences and through peer-reviewed publications.