Fore/ hind wing differentiation in the red flour beetle, Tribolium castaneum. Y. Tomoyasu¹, S.R. Wheeler², R.E. Denell¹. 1) Division of Biology, Kansas State Univ, Manhattan, KS; 2) Department of Genetics, Washington Univ, St. Louis, MO.

   
   To understand how changes in patterning mechanisms have contributed to the evolution of morphological diversity, we are analyzing the gene regulatory network of wing development in Tribolium and comparing it to that of Drosophila.
   In Drosophila, the T2 wing is used for flight, while the T3 haltere is highly reduced and used only for balance. In Tribolium, however, the flight wings are located on T3, while T2 bears highly sclerotized elytra that are used for body cover. Also, morphologies of the wings (such as vein pattern and the positioning of sensory organs) are different from those of Drosophila.
   To identify the changes in developmental programs that have contributed to these morphological differences, we first analyzed the expression patterns of several Hox genes, including Ubx, and more than fifteen genes that might be important for wing development in Tribolium. Like Drosophila Ubx, which represses expression of some wing genes in T3 haltere, the Tc Ubx protein is expressed in T3 elytra but not T2 wing. However, many genes we examined, including the target genes of Ubx in Drosophila, are expressed similarly in T2 elytra and in T3 wing, suggesting Tc Ubx does not appear to repress the same set of genes as it does in Drosophila. We also noticed that spalt, iroquois and achaete are expressed differently in elytra and wing. To further analyze the functional requirement of these genes, we have established a larval RNAi technique to knock down gene function from the late larval to adult stage. A control experiment using a marker gene indicates that the RNAi effect lasts more than a week after dsRNA is injected. Our preliminary data for larval RNAi of several Hox genes suggests that in Tribolium Hox proteins might regulate the expression of wing genes very differently than in Drosophila. The expression and phenotypic analyses of these RNAi beetles as well as several wing/elytra mutants will be presented.