Meeting Abstract

P2.101  Friday, Jan. 4  RNAi suppression of a storage protein in Romalea microptera. MCMAHON, JF*; ZOSHAK, JJ; GHONAIM, M; HAHN, D; BORST, DW; Univ. of Central Florida; Univ. of Central Florida; Univ. of Central Florida; Univ. of Florida; Univ. of Central Florida dborst@mail.ucf.edu

Many insect species use excess amino acids to synthesize storage proteins (SPs) which accumulate in the hemolymph or fat body and are utilized later during times of increased metabolic need (e.g., molting, reproduction). The hexamerins are one common class of SPs. The eastern lubber grasshopper, Romalea microptera, has three hexamerin SPs in its hemolymph which have apparent molecular weights of 90, 270, and 500kDa on native polyacrylamide gel electrophoresis (nPAGE). Of these, the 90 kDa protein is the most abundant and also a major binding protein for juvenile hormone (JH). To study the biological importance of the 90 kDa protein, we treated males on the first day of the fourth instar with 0, 1, and 3 �g of double stranded RNA (RNAi) for the 90 kDa mRNA. Animals from each treatment group were analyzed on days 3, 6, and 9. The mRNA levels of the 90kDa protein (measured by real time PCR) were less than one percent of the levels in control animals on all three days. The levels of mRNA for the 270 and 500 kDa proteins were not affected. Levels of total hemolymph protein (measured by Bradford) were not significantly different in treated and non-treated animals. However, analysis of hemolymph by nPAGE showed a marked decrease of the 90kDA protein and an increase in the levels of the 500 kDa protein. Finally, JH levels in treated animals were not different from the levels in controls. These data indicate that the lubber grasshopper compensates for the absence of 90 kDa by increasing the amount of other hemolymph proteins (e.g., the 500kDa). Understanding the role of storage proteins in the lubber grasshopper will require suppressing the production of all three proteins. (Supported by NSF grant 0442412).