Abstracts - Deutsche Zoologische Gesellschaft

Developmental Biology Symposium 31O DB.1 (Su) - ENEvolution of posterior patterning in a short germ beetleChristian Schmitt, Michael SchoppmeierBiology Department, Developmental Biology Unit, University of Erlangen-NurembergSymmetry breaking events during early embryogenesis are the fundamental basis for the developmentof differentiated embryos throughout the animal kingdom. In the long germ insect Drosophila,these symmetry-breaking events lead to protein gradients along the antero-posterior axis, whichserve as starting points for the regionalization of the embryo. Itis still not completely clear to whichdegree these early acting antero-posterior systems are conserved in other insect species. To addressthis question, we have analyzed the role of the posterior determinants nanos and pumilio duringaxis formation of the shortgerm insect Tribolium castaneum. We found that Tc-pum and Tc-nos areimportant for abdomen formation and are involved in blastodermal patterning. Embryos resultingfrom nanos or pumilio RNAi do not form the full set of abdominal segments. In addition to thatand in contrast to Drosophila they also show homeotic transformations or deletions of gnathal andhead-segments. These transformations are due to misregulation of Hox-gene expression, while thedeletions are already detectable during blastodermal stages. Interestingly, these phenotypes resemblethose of Tc-gap-genes, which also show homeotic transformations.Thus, although Tc-nos andTc-pum are important for blastodermal patterning and axis elongation, their function differs fundamentallyfrom their Drosophila orthologs, which may be due to the special needs of short germ,respectively long germ development.O DB.2 (Su) - ENThe role of frizzled dependent Wnt-signaling in body axis elongation and appendageformation in TriboliumReinhard Schröder 1 , Anke Beermann 2 , Rebekka Lutz 21Genetik, Universität Rostock; 2 Interf. Institut für Zellbiologie, Abt. Genetik der Tiere, UniversitätTübingenShort germband embryos establish their primary head to tail axis during embryogenesis by consecutivelyadding segments to the anterior body part from a posterior located growth zone. At which levelof the segmentation hierarchy Wnt-signalling is required during embryogenesis remains unknown.By expression analysis of the Wnt-receptors Tribolium-frizzled 2, we identify a novel region in theembryo involved in Wnt-dependent axis elongation: the presegmented region anterior to the growthzone. Simultaneously knocking down the function of the redundant Wnt receptors Frizzled 1 andFrizzled 2 using RNAi results in a dwarfed embryonic phenotype. We show here that Wnt signalingis primarily required for the elongation of the body axis, since in Tc-frizzled RNAi embryos the growthzonecollapses before the complete set of abdominal segments have formed. These defects occur atthe level of pair-rule gene regulation. The onset of Even-skipped expression takes place while thedevelopment of secondary Even-skipped pair-rule stripes is discontinued and leads to the cessationof the segmentation process. Whereas Fz-1 and Fz-2 act completely redundant in the segmentationprocess of the long germband insect Drosophila, the knock down of Frizzled 1 alone leads to shorterand misshaped appendages in Tribolium. This points to a novel role of Fz-1 dependent Wnt signallingin appendage formation. The single knock down of Tribolium Frizzled-2 has no effect.