Stress gene (hsp70) sequences and quantitative expression in Milnesium tardigradum (Tardigrada) during active and cryptobiotic stages.
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.
Schill
Ralph O
RO
Animal Physiological Ecology, Zoological Institute, University of Tübingen, Konrad-Adenauer-Str. 20, D-72072 Tübingen, Germany. ralph.schill@uni-tuebingen.de
Steinbrück
Günther H B
GH
Köhler
Heinz-R
HR
D000064:Acclimatization / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004587:Electrophoresis, Agar Gel; D005453:Fluorescence; D015870:Gene Expression; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D007448:Invertebrates / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D018840:HSP70 Heat-Shock Proteins