Early pattern formation in the embryo of the fruit fly, Drosophila melanogaster, has been particularly well studied and has resulted in the elucidation of an intricate developmental program that controls Drosophila embryonic morphogenesis. Drosophila, however, represents a phylogenetically advanced and specialized insect. Previous experiments involving mechanical manipulations of developing insect embryos suggest that early Drosophila development differs substantially from that of other, less evolved, insects. These differences have also been implicated by more recent molecular data. The aim of this project is to further examine the extent to which mechanisms of segmentation may differ between different insects and to analyze the evolution of the molecular system that controls the process of insect segmentation. This will be done by isolating homologs of Drosophila segmentation genes in Schistocerca (grasshopper), an insect representing a more primitive mode of development. PCR and reduced stringency hybridization will be used to isolate Schistocerca homologs of the Drosophila segmentation genes even-skipped, hairy, runt, hunchback and Kruppel. The expression patterns of these Schistocerca genes will be analyzed by in situ hybridization and immunohistochemistry. By examining the extent to which these genes are utilized during Schistocerca development, this project will significantly advance us towards our long term goals of understanding the evolution of the process of segmentation and its underlying molecular systems. These results will also significantly affect our views on the extent to which Drosophila developmental strategies may be shared by other organisms both within and outside the phylum Arthropoda. Homologs of several of the genes involved in Drosophila segmentation have been identified in organisms of other phyla. In particular, a number of homologs have been identified in vertebrates such as Xenopus, mice, and humans. A better understanding of the range of functions of these genes in insects will help clarify potential roles for their homologs in vertebrate development. In addition, the genes in this study are all thought to control cell differentiation by exerting control on the expression of other genes. Thus, the results of this project will provide insights into the evolution of molecular mechanisms capable of controlling cell differentiation. Such information is important in understanding the mechanisms that control not only normal development, but also abnormal conditions resulting from improper cell determination and regulation.