Meeting Abstract

P2.125  Sunday, Jan. 5 15:30  RNAi mediated knockdown of KAAT1 and measurement of surface area in the Manduca sexta midgut. PARMELEE, A.L.**; GOULDER, K.D.; GILLEN, C.M.; ITAGAKI, H.; Kenyon College; Kenyon College; Kenyon College; Kenyon College itagaki@kenyon.edu

To investigate factors in the gastrointestinal system that influence metabolic scaling, we measured midgut surface area and manipulated nutrient transporter expression in larvae of the tobacco hawkmoth (Manduca sexta). Surface area was measured in composite micrographs of more than 150 sections from more than 20 larvae ranging from first through fifth instar. The scaling exponent for the relationship between midgut luminal perimeter and body mass was 0.49, indicating that midgut surface area becomes increasingly folded as larvae grow. Anterior, middle, and posterior midgut all scaled with approximately the same relationship. In previous work, we have measured a 2 to 3-fold increase in the expression of mRNA encoding the potassium-amino acid transporter KAAT1 in 5th compared to 4th instar larvae. To assess the functional consequences increased of KAAT1 in the 5th instar, we used RNAi interference to decrease KAAT1 expression. Injections of a 453bp KAAT1 dsRNA on three consecutive days caused an approximately 6-fold decrease in expression of KAAT1 in middle midgut. In contrast, KAAT1 levels in the posterior midgut were unchanged, while mRNA encoding the related gene CAATCH1 were decreased approximately 10-fold. (NSF-DMS0827208)