Meeting Abstract

P2.126  Sunday, Jan. 5 15:30  It takes guts to specialize: Digestive enzymes of Greater sage-grouse resist inhibition by chemical defenses of sagebrush PITMAN, E.*; KOHL, K.D.; CONNELLY, J.W.; DEARING, M.D.; FORBEY, J.S.; Univ. of Utah; Univ. of Utah; Idaho Dept. of Fish and Game; Univ. of Utah; Boise State Univ. e.x.pitman@gmail.com

Greater Sage-grouse (Centrocercus urophasianus) are dietary specialists on sagebrush (Artemisia spp.), which are heavily defended by a variety of plant secondary compounds (PSCs). Monoterpenes, a group of PSCs found in sagebrush, may inhibit grouse digestive enzymes, consequently restricting nutrient availability. Some herbivores have evolved digestive enzymes that are tolerant to high concentrations of PSCs; however, such an adaptation has never been studied in an avian herbivore. We hypothesized that sage-grouse produce tolerant digestive enzymes to overcome the inhibitory effects of monoterpenes. We measured the inhibitory effects of isolated monoterpenes on aminopeptidase-N, a digestive enzyme that hydrolyzes dietary proteins. Inhibition rates were compared between the sage-grouse and a related, naïve animal, the domestic chicken (Gallus gallus). Compared to chickens, the aminopeptidase-N enzyme produced by sage-grouse retained ~2.5-times higher relative activity at high concentrations of monoterpenes, such as borneol and 1,8-cineole. This research demonstrates that adaptations of digestive enzymes may be a common trait in specialist herbivores. We hypothesize that these adaptations allow herbivores to maximize digestion and absorption of nutrients despite high concentration of PSCs in their diet. Future research should investigate the molecular changes in enzyme structure that yield this tolerance.