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The versatile waterflea –

Sequence of “ecoresponsive” Daphnia genome revealed

Munich, 02/04/2011

Water fleas are highly adaptable organisms that can react rapidly to alterations in environmental conditions. The Daphnia Genomics Consortium, an international group of researchers that includes three from LMU – biologist Professor Christian Laforsch and biochemists Dr. Georg J. Arnold and Dr. Thomas Fröhlich (Genzentrum-LAFUGA), has now sequenced the complete genome of the water flea Daphnia pulex. To their surprise, the team found that the water flea has more genes in its genome than any other animal yet sequenced. Humans have about 23,000 protein-coding genes, but Daphnia pulex can boast of having over 31,000. The reason for this difference appears to be an elevated rate of gene duplication in the course of its evolution. This provided raw material for the evolution of new functions, which in turn allowed the species to respond appropriately to frequently changing environmental conditions and explains its extraordinary phenotypic plasticity. Indeed, one-third of all its genes have no homologs in other organisms, and the LMU investigators showed that members of this class are activated in response to environmental stressors.
(Science, 4 February 2011)

In the context of the comprehensive analysis of the Daphnia genome led by Dr. John Colbourne of Indiana University (Bloomington, USA), LMU Professor Christian Laforsch of the Department of Biology II and his colleagues Dr. Georg J. Arnold and Dr. Thomas Fröhlich from the Laboratory for Functional Genome Analysis at LMU’s Genzentrum (LAFUGA) took a close look at patterns of gene expression in the organism.

With the aid of state of the art mass spectrometry techniques the LMU researchers were able to detect and identify the products of active genes. Further studies of the RNA molecules transcribed from the genomic DNA (which go on to program protein synthesis), carried out in cooperation with Laforsch, then showed that members of the novel Daphnia gene set are activated when the organisms are exposed to environmental stressors. One can therefore infer that the protein products of these genes play important roles in enabling the animals to adapt to varying environmental conditions.

 “The water flea occupies a central position in the food chain, which makes it a keystone species in freshwater ecosystems,“ says Laforsch. “The organisms are extremely sensitive to the presence of toxins in their habitats, so that they serve already as model organism in ecotoxicology. In addition, a wealth of data on the ecology and evolutionary biology of Daphnia is available, so that the water flea has all the hallmarks of an ideal model system for the study of the genetic mechanisms underlying adaptations to diverse environmental factors.”

The time is ripe for this organism to take on a starring role in the biosciences. With the publication of the genome sequence, further in-depth investigations are now possible. These will ultimately tell us which gene functions are linked to which phenotypic traits, and elucidate the roles of specific genes in enabling adaptation to environmental variation – including climate change. (göd)


"The Ecoresponsive Genome of Daphnia pulex"
Colbourne, J.K., M.E. Pfrender, D. Gilbert, W.K. Thomas, A. Tucker, T.H. Oakley, S. Tokishita, A. Aerts, G.J. Arnold, M. Kumar Basu, D.J. Bauer, C.E. Cáceres, L. Carmel, C. Casola, J.-H. Choi, C. Detter, Q. Dong, S. Dusheyko, B.D. Eads, T. Fröhlich, K.A. Geiler-Samerotte, D. Gerlach, P. Hatcher, S. Jogdeo, J. Krijgsveld, E.V. Kriventseva, D. Kültz, C. Laforsch, E. Lindquist, J. Lopez, J.R. Manak, J. Muller, J. Pangilinan, R.P. Patwardhan, S. Pitluck, E.J. Pritham, A. Rechtsteiner, M. Rho, I.B. Rogozin, O. Sakarya, A. Salamov, S. Schaack, H. Shapiro, Y. Shiga, C. Skalitzky, Z. Smith, A. Souvorov, W. Sung, Z. Tang, D. Tsuchiya, H. Tu, H. Vos, M. Wang, Y.I. Wolf, H. Yamagata, T. Yamada, Y. Ye, J.R. Shaw, J. Andrews, T.J. Crease, H. Tang, S.M. Lucas, H.M. Robertson, P. Bork, E.V. Koonin, E.M. Zdobnov, I. Grigoriev, M. Lynch and J.L. Boore
Science 331:555-561, 4 February 2011

Professor Dr. Christian Laforsch
Department of Biology II, LMU Munich
Phone: +49 (0) 89 / 2180 - 74252

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