04-P013 A temporal modulation of FGF, Wnt, BMP and Retinoic Acid signalling is required for neural crest induction

The body axes of many animals are initially patterned by the asymmetric distribution of maternal mRNAs and proteins in the oocyte. In Drosophila, these maternal factors are synthesized by the 15 nurse cells that connect to each oocyte within the ovary. However, insect ovaries fall into three anatomical categories, of which Drosophila represents only one. The telotrophic meroistic ovaries of the true bugs (Hemiptera), for example, possess a single group of syncytial nurse cells that connect to all oocytes simultaneously via extended nutritive tubes. The panoistic ovaries of basal insects including crickets (Orthoptera) do not possess nurse cells. Little is known about the production or localization of maternal factors within the developing oocytes of insects possessing these different ovary types. To address this issue, we have begun to characterize the ovarian and embryonic transcriptomes of a Hemipteran (the milkweed bug, Oncopeltus fasciatus) and an Orthopteran (the cricket Gryllus bimaculatus) using 454 pyrosequencing. Both of these species have rich histories as laboratory species, and both possess large ovaries that facilitate live imaging and microinjection. Our sequence data will allow us to identify orthologs of candidate genes involved in a variety of embryonic patterning processes, and will lay the groundwork for future studies on the development and evolution of insect body plans. Additionally, these sequences will augment the relatively few genomic resources available for hemimetabolous insects, thereby contributing to our understanding of genomic evolution during the 330 million years since the divergence of Hemimetabola and Holometabola from their last common ancestor.