Regulation of Diverse Modes of Segmentation in Coleoptera (Beetles). Jie Xiang¹, Alison Heffer¹, Leslie Pick^1,2. 1) Program in Molecular & Cell Biology, University of Maryland, College Park, MD; 2) Department of Entomology, University of Maryland, College Park, MD.

   A hierarchy of genes regulating segmentation in Drosophila melanogaster has been well-characterized. Drosophila is a highly specialized long-germ insect with all segments specified simultaneously at the blastoderm stage prior to gastrulation. However, in short- and intermediate-germ insects, only anterior segments are formed before gastrulation; additional segments are added sequentially as the embryo grows. Expression data and functional studies suggest that orthologs of some Drosophila gap and pair-rule genes function differently in other arthropods. To understand how patterning mechanisms evolved, we are examining ftz and ftz-f1 sequence, expression and function in short, intermediate- and long-germ beetles, Tribolium casteneum, Dermestes maculatus and Callosobruchus maculatus, respectively. While both Tc-ftz and Tc-ftz-f1 are expressed in pair-rule stripes, Tc-ftz-f1 is also expressed ubiquitously in pre-blastoderm embryos. Functional studies using RNAi revealed a role for Tc-ftz-f1 in regulating alternate Engrailed stripes, establishing ftz-f1 as a pair-rule gene in Tribolium. In addition, Tc-ftz-f1 is required at later stages of embryogenesis for cuticle development. Preliminary in situ hybridization in the other beetle species suggests striped patterns of ftz and ftz-f1 expression at early stages of development. RT-PCR result suggests Dmac-ftz-f1 is maternally deposited, similar to Tc-ftz-f1. Expression patterns of ftz and ftz-f1 in these two species will be further examined and interaction of their protein products will be tested. Next, RNAi will be performed to study functions of ftz and ftz-f1 in these beetles. These studies will shed light on the evolution of the genetic basis underlying segmentation across arthropod taxa.