Function and Evolution of Sensory Signaling Systems in Selected Marine Invertebrate Groups.
Over the past years, a range of invertebrate genomes have been completely sequenced including several marine representatives [Strongylocentrotus purpuratus (sea urchin), Ciona intestinalis (sea squirt), Trichoplax adherens, Aplysia californica (sea hare), Brachiostoma floridae (lancelet), Capitella sp. I (polychaete worm) Lottia gigantean (Limpet), Nematostella vectensis (sea anemone)]. In collaboration with Dr Leonid Moroz, we are complementing several of these projects with transcriptom data. Specifically, we used standard and innovative massive parallel sequencing systems (e.g. 454 Life Sci pyrosequencing) and have obtained more than 900,000 expressed sequenced tags (ESTs) from representative of these species. The existing collection is the largest database available from the Lophotrochozoa superclade of the animal kingdom and from Placozoa. Work with these transcriptomes has not only helped to clarify the position of these organisms within metazoan phyla (Bourlat et al. 2006) but also revealed many new interesting neuropeptides and transcription factors that appear to have been evolutionarily lost in the ecdysozoan or vertebrate model systems (Moroz et al. 2006). Several research directions currently pursued in my lab are designed to answer fundamental questions about the interactions between genotype and phenotype and the modulation of this interaction by the environment. By taking advantage of this novel sequence information and combining it with functional genomics tools, we are addressing questions such as: 1) What is the regulatory architecture underlying the metamorphic transitions in marine invertebrate species or more specifically: how to marine invertebrate larvae that have reached metamorphic competence modulate environmental sensory input ultimately leading to the dramatic morphological and physiological changes seen during the metamorphic transition? and 2) How do organisms such as Trichoplax adherens that have a comparably simple tissue organization coordinate behaviors (feeding, locomotion, mating etc.) in response to environmental cues? Trichoplax adherens is the only known member of the phylum placozoa. It has only four cell types and reproduces asexually by binary fission or budding (production of swarming life history stages). A molecular signature for sexual reproduction has also recently been confirmed (Signorovitch et al. 2006). Its simplicity, basal position and easy laboratory maintenance make it an ideal organism to study cell identity and function in the context of exciting evolutionary questions, such as the origin of neuron-like cells and their genetics repertoire (pro-neuronal genes).