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Water fleas and stress

LMU Press Release


The life of a water flea is full of alarms. The tiny freshwater crustaceans belonging to the genus Daphnia inhabit an environment that is teeming with predators and subject to a plethora of potentially threatening environmental fluctuations. How does the Daphnia genome respond as species adapt to ecological stressors? This question is at the heart of the international research project STRESSFLEA, which is being funded for three years by a 1.5 million Euro grant from the European Science Foundation (ESF). The collaboration will try to get insight into the genomic underpinning of genetic adaptation to specific stressors. The participating teams also hope to reconstruct the course of genomic evolution in Daphnia over the past few hundred years. PD Dr. Christian Laforsch and Dr. Georg Arnold of LMU have taken on responsibility for the area of proteomics. “We intend to survey proteins encoded by the Daphnia genome“, says Laforsch, ”in order to analyse how patterns of gene activity change as the organism encounters various environmental challenges”. STRESSFLEA is part of EuroEEFG (short for ”Ecological and Evolutionary Functional Genomics“). Among other things, this program aims to work out how genes respond to environmental stressors, such as those associated with climate change, and the presence of parasites or chemical pollutants.

The fruitfly Drosophila melanogaster, baker’s (and brewer’s) yeast Saccharomyces cerevisiae and the nematode Caenorhabditis elegans are genetically and experimentally tractable organisms that are particularly well suited for the investigation of problems of biological and medical relevance. This is the basic reason why they, along with several others, have become established model systems in the laboratory. However, novel and interdisciplinary approaches sometimes make it necessary to turn to other organisms as models. “Over the past several years, so much information regarding the activity and regulation of genes has been accumulated that ecologists and evolutionary biologists now wish to relate this knowledge to adaptation and organismic evolution”, says  LMU-biologist PD Dr. Christian Laforsch. “In this context, the water flea Daphnia appears to be an ideal model, because large amounts of ecological and evolutionary data on this organism are available. Its major advantage is that one can follow how populations adapt to varying environmental parameters from the ecological down to the genetic level.“

The EU-wide collaboration ”How to live in a mosaic of stressors – an ecological genomics approach on the water flea Daphnia“ (STRESSFLEA) is devoted to elucidating the genetic changes that underpin adaptation, and will focus on four main areas. The first priority is to obtain insight into the genomic basis of genetic adaptation to specific stressors by identifying candidate genes underlying specific adaptive responses along environmental gradients and validating their involvement in responses to specific stressors. These genes will then be functionally coupled with a particular adaptive trait by linking their expression to variations in trait values and placing them in genetic networks that are linked to variation in the trait of interest. The third task is to dissect the genetic mechanisms that allow Daphnia populations to respond to multiple stressors. Finally, the researchers hope to retrace the course of evolution in Daphnia populations over the last few hundred years. This ambitious goal appears feasible because dormant Daphnia eggs remain viable for up to several centuries and accumulate as stratified and datable egg banks in lake sediments. Analysis of genetic markers linked to candidate genes in such material will permit the investigators to reconstruct changes in ecologically relevant traits in natural populations over time spans of up to several centuries.

Together with the LMU biochemists Georg Arnold und Thomas Fröhlich, Laforsch will lead the analysis of the Daphnia proteome. A proteomics-based approach will be employed to detect differences and similarities in protein expression in Daphnia exposed to a variety of environmental stressors.The overriding importance of elucidating the links between genetics, ecology and evolutionary biology emerges clearly from investigations previously carried out by Laforsch. “The crown of thorns is a structure found on the head of a particular Daphnia variety and was regarded as a species-specific trait“, he says. “We showed that the ability to make it was not confined to a single lineage. The crown actually serves as a defence against a predatory shrimp, and its formation is induced if the shrimp is present in the water flea’s habitat. The study clearly demonstrates the value of genetic data for the understanding of ecological and evolutionary processes.“


Daphnia pulex Genome Project – Daphnia Genome Consortium“
LC-MS/MS-based proteome profiling in Daphnia pulex and Daphnia longicephala: The Daphnia pulex genome database as a key for high throughput proteomics in Daphnia”.
Fröhlich T., Arnold G. J., Fritsch R., Mayr T., Laforsch C.
BMC Genomics, 21. April 2009

Daphnia and the ”crown of thorns“”A ’crown of thorns’, an exceptional inducible defense, protects Daphnia against an ancient predator“,
Petrusek A., Tollrian R., Schwenk K., Haas A., Laforsch, C.
PNAS, vol 106, pp 2248-2252, 17. February 2009


Priv. Doz. Dr. Christian Laforsch
Department Biology II,  LMU Munich
Phone: +49 (0) 89 / 2180 – 74252
Fax: +49 (0) 89 / 2180 - 74204
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