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First published online April 8, 2004
Journal of Experimental Biology 207, 1607-1613 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00935
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Stress gene (hsp70) sequences and quantitative expression in Milnesium tardigradum (Tardigrada) during active and cryptobiotic stages

Ralph O. Schill1,*, Günther H. B. Steinbrück2 and Heinz-R. Köhler1

1 Animal Physiological Ecology, Zoological Institute, University of Tübingen, Konrad-Adenauer-Str. 20, D-72072 Tübingen, Germany
2 Molecular Biology, Institute for Cell Biology, Auf der Morgenstelle 28, D-72076 Tübingen, Germany

* Author for correspondence (e-mail: ralph.schill{at}uni-tuebingen.de)

Accepted 12 February 2004

The eutardigrade Milnesium tardigradum can undergo cryptobiosis, i.e. entry into a reversible ametabolic stage induced by dehydration, cooling and, probably, osmotic and anoxic stress. For the first time in tardigrades, we described partial sequences of three heat-shock protein (hsp70 family) genes and examined gene expression on the way from an active to a cryptobiotic and back to an active stage again. Results showed different patterns of gene expression in the hsp70 isoforms. All three isoforms seem to be true heat-shock proteins since transcription could be clearly enhanced by temperature elevation. Isoform 1 and, at a lower level, isoform 3 do not seem to have a specific function for cryptobiosis. By contrast, transcription of isoform 2 is significantly induced in the transitional stage between the active and the cryptobiotic stage, resulting in a comparatively high mRNA copy number also during cryptobiosis. This pattern of induction implies that isoform 2 is the most relevant hsp70 gene for M. tardigradum individuals entering the cryptobiotic stage.

Key words: anhydrobiosis, cryptobiosis, Eutardigrada, heat-shock protein, stress protein, hsp70






© The Company of Biologists Ltd 2004