Abstracts - Deutsche Zoologische Gesellschaft

Physiology Symposium 87especially concerning the spatial orientation of certain FU types. On the basis of the two resultingmolecular models it is now the task to interpret these differences in terms of allosteric interactionmechanisms, but also to reveal possible pitfalls.O PH.13 (Mo) - ENThe acid-stress response of Daphnia pulex: insights from a proteome analysisRalph Pirow 1 , Sebastian Benkhoff 1 , Johannes Madlung 2 , Claudia Fladerer 2 , Tobias Lamkemeyer 21Institut für Zoophysiologie, Universität Münster; 2 Proteom Centrum TübingenHow animals cope with environmental changes has been, and still is, a major question in organismalbiology. The increasing availability of whole-genome sequence information offers new opportunitiesto connect well-characterized organismal responses with variations in gene expression. By usingtwo-dimensional gel electrophoresis and mass spectrometry, we analyzed the molecular mechanismsof acid-stress acclimation in the planktonic microcrustacean Daphnia pulex, which is an emergingmodel for ecological and toxicological genomics. Compared to the control animals raised undercircumneutral pH conditions, animal acclimated to acidic conditions (pH 6.0) showed a reducedexpression of digestive enzymes (laminarinase, serine proteases), whereas vitellogenin (VTG), hemoglobin(Hb) and a glycolytic enzyme (enolase) remained constitutively expressed. In contrast, aninduction of digestive enzymes and a suppression of VTG and Hb expression was observed in pH5.5 acclimated animals. Most remarkable among the acid-sensitive protein expressions was the upregulationof proteins involved in the cellular stress response (prohibitin, glutathione S-transferase,carbonyl reductase) and in the cellular calcium metabolism (calcyphosine), as well as the downregulationof a protein involved in membrane turnover (GM2 gangliosid activator protein).O PH.14 (Mo) - ENThe role of polyamine synthesis in stress tolerance of Caenorhabditis elegansAlexander Heinick, Tim Schlesinger, Danica Spiess, Stefan Roth, Eva Liebau, Kai LüersenInstitut für Zoophysiologie, Universität MünsterThe polyamines putrescine and spermidine are simple aliphatic polycations found in all living organisms.It is well established that polyamines are crucial for biological processes such as developmentand growth. However, an increasing number of evidence indicates that they also function asprimordial stress molecules. Previous studies on polyamines and environmental stress have beenperformed mainly in prokaryotes and plants. To investigate the role of polyamines in stress tolerancein an animal model system, we used free-living nematode Caenorhabditis elegans. Its polyaminemetabolism encompasses a synthesis pathway consisting of the enzymes ornithine decarboxylase(ODC), S-adenosylmethionine decarboxlyase (SMD) and spermidine synthase (SPDS). The regulatoryODC converts ornithine into putrescine, the SMD together with the SPDS is essential forspermidine synthesis. Furthermore, the worms take up polyamines from the environment. C. elegansodc-1 and smd-1 null mutants as well as mutants with an impaired polyamine uptake system weretested against several environmental stressors. The odc-1 mutant exhibits a drastically reduced tolerancetowards heat stress at 32°C. Interestingly, neither the smd-1 mutant nor the polyamine uptakemutants showed an altered heat stress tolerance, indicating that putrescine but not spermidine isresponsible for the observed effect. Stress tolerance and the acute stress response will be correlatedwith the amounts of transcript and protein as well as with the polyamine content.