Abstracts - Deutsche Zoologische Gesellschaft

Developmental Biology Posters 121P DB.5 - ENEssential roles of MMPs in the development of Tribolium castaneum: an alternativemodel for MMP researchEileen KnorrAngewandte Entomologie, Justus-Liebig-Universität GießenMatrix metalloproteinases (MMPs) are evolutionarily conserved zinc-endopeptidases with multifunctionalroles in animal development and homeostasis. Here, we identified seven MMP homologs,MMP-1, MMP-2, MMP-3, and a number of virus-like MMP sequences with yet unknown functionsin the red flour beetle Tribolium castaneum, an important model insect for developmental studies.Phylogenetic analysis elucidates that MMP-1, MMP-2 and MMP-3 are homologues to describedMMPs from other animals. To explore role of Tribolium MMPs in vivo we determined timely shiftedenhanced expression levels of MMP-1, MMP-2, MMP-3, but not of a virus-like MMP (MMP-4),respectively, during metamorphosis using real-time RT-PCR. Furthermore, we silenced these fourMMPs of by dsRNA-mediated genetic interference. Knock-down of MMP-1 results in individualsthat arrest in larval to pupal transformation during metamorphosis, while knock-down of MMP-2,MMP-3, or MMP-4 did not impaired development of pupae and imagoes. Furthermore, all MMPknock-down animals exhibit normal egg laying rates and first instar larvae hatch normally. However,parenteral RNAi-mediated MMP-1 knock-down resulted in offspring with non-lethal defectsin posterior tracheal trunks, implicating a role in trachea development, whereas MMP-2 knock-downresulted in abnormal intestines with over 90% mortality in first instar larvae, implicating a role in gutdevelopment. Compared to results from the fruit fly Drosophila melanogaster our results from thebeetle Tribolium demonstrate some striking similarities but also obvious differences of MMP rolesin these two holometabolous insect species whose lineages have split from their common ancestormore than 270 millions of years ago.P DB.6 - ENUltrastructure of the Drosophila wing hearts: first example of adult syncytial musclesderiving from the heart fieldChristine Lehmacher 1 , Markus Tögel 1 , Günther Pass 2 , Achim Paululat 11University of Osnabrück; 2 University of Vienna, AustriaIn Drosophila, hemolymph circulation in the wings is accomplished by two small muscular pumpsthat are located bilaterally in the scutellum and function independently of the heart. Although clearlymyogenic, wing hearts neither share a common lineage with the contractile cardiomyocytes, norderive from somatic adult muscle precursors. Surprisingly, they originate from a specific subset ofembryonic Even-skipped positive pericardial cells, which arise in the heart field. In this study, wehave analyzed the wing hearts at an ultrastructural level to investigate the fine structure of musclesderiving from these new adult progenitors. We found that, like somatic muscles arising from adultmuscle precursors, the wing heart muscles are multinucleated syncytial muscle fibres that are attachedto the cuticle via epidermal tendon cells. Their myofibrils are radially arranged around centralnuclei and consist of well defined sarcomeres with discontinuous Z-discs, A-bands, and I-bands.However, in addition to these striking similarities with somatic muscles, wing heart muscles alsoshow mitochondria filled outpockets of the cell membrane between two adjacent Z-discs, which arecharacteristic for heart muscles. We conclude that wing hearts represent somatic muscles that eitherhave similar physiological requirements like the heart, or their fine structure is influenced by factorsexpressed in the heart field, which account for the characteristic outpockets.