Molecular mechanisms underlying sipunculan bodyplan formation

Sipunculans (or peanut worms) lack any obvious signs of segmentation in their adult body and their origin and relation to segmented worms have been highly debated. Recent morphological studies have suggested traits of segmentation during their development (Kristof et al. 2008, 2011, Wanninger et al. 2009). Interestingly, this segmental organisation is lost as the animals approach metamorphosis, thus suggesting that (1) sipunculans stem from a segmented ancestor as do the Annelida, and (2) that body segmentation is more evolutionary labile than previously thought. Whether or not this cryptic segmentation during sipunculan ontogeny can be confirmed on a molecular level will be investigated in the proposed project. Therefore, an expressed sequence tags (ESTs) library will be generated and screened for genes known to play crucial roles in the segmentation process of the well- studied annelid, arthropod and chordate model organisms. Thus, the main objective of the project is to analyse gene expression during development of a model sipunculan, Themiste pyroides, which I have shown to be ideally suited for these kinds of studies (preliminary data in my PhD thesis, Kristof 2011). The project will mostly take place in Univ.-Prof. DDr. Andreas Wanninger`s group, with its newly established molecular laboratory at the Department of Integrative Zoology, University of Vienna, Austria. A detailed analysis of the transcriptome datasets including the necessary bioinformatics will take place in collaboration with Christoph Bleidorns Molecular Evolution and Animal Systematics group at the University of Leipzig, Germany. In situ probes of developmental genes will be generated from the transcriptome library and/or, if necessary, by PCR screenings. Expression analysis of developmental genes (e.g., hairy, notch, delta, wingless, labial, caudal, engrailed, even-skipped) - which are known to be involved in the segmentation in annelids, arthropods and chordates - during sipunculan development will provide important insights into their role in sipunculan body patterning. Moreover, the current establishment of large-scale EST libraries and expression analysis of "segmentation genes" in two aculiferan molluscs, Wirenia argentea (Solenogastres) and Ischnochiton hakodadensis (Polyplacophora), in the laboratory of A. Wanninger will enable comparative analysis of "segmentation" and other body patterning genes across vermiform lophotrochozoan phyla. This comparative approach should provide important insights into the evolution of segmentation, which is considered one of most fundamental questions in the field of evolution and development.