Stress response in tardigrades: differential gene expression of molecular chaperones
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Semi-terrestrial tardigrades exhibit a remarkable tolerance to desiccation by entering a state called anhydrobiosis. In this state, they show a strong resistance against several kinds of physical extremes. Because of the probable importance of stress proteins during the phases of dehydration and rehydration, the relative abundance of transcripts coding for two α-crystallin heat-shock proteins (Mt-sHsp17.2 and Mt-sHsp19.5), as well for the heat-shock proteins Mt-sHsp10, Mt-Hsp60, Mt-Hsp70 and Mt-Hsp90, were analysed in active and anhydrobiotic tardigrades of the species Milnesium tardigradum. They were also analysed in the transitional stage (I) of dehydration, the transitional stage (II) of rehydration and in heat-shocked specimens. A variable pattern of expression was detected, with most candidates being downregulated. Gene transcripts of one Mt-hsp70 isoform in the transitional stage I and Mt-hsp90 in the anhydrobiotic stage were significantly upregulated. A high gene expression (778.6-fold) was found for the small α-crystallin heat-shock protein gene Mt-sHsp17.2 after heat shock. We discuss the limited role of the stress-gene expression in the transitional stages between the active and anhydrobiotic tardigrades and other mechanisms which allow tardigrades to survive desiccation.
KeywordsAlpha-crystallin protein Anhydrobiosis Cryptobiosis Heat-shock protein Tardigrada Milnesium tardigradum
The authors wish to thank Eva Roth for maintaining the tardigrade culture. This study is part of the project FUNCRYPTA (0313838A, 0313838B and 0313838E), funded by the German Federal Ministry of Education and Research, BMBF.
- Baumann H (1922) Die Anabiose der Tardigraden. Zool Jahrb Abt Allg Zool Physiol Tiere 45:501–556Google Scholar
- Crowe LM (2002) Lessons from nature: the role of sugars in anhydrobiosis. Comp Biochem Physiol A Comp Physiol 131:505–513Google Scholar
- McGee B, Schill RO, Tunnacliffe A (2005) Hydrophilic proteins in invertebrate anhydrobiosis. Annual Meeting of the Society for Integrative and Comparative Biology (SICB), San Diego, USAGoogle Scholar
- Schill RO, McGee B, Tunnacliffe A (2005). Molecular adaptation to extreme dehydration in tardigrades: Hsp70 gene expression, and putative LEA protein induction during cryptobiosis. International Symposium on the Environmental Physiology of Ectotherms and Plants (ISEPEP), Roskilde, DenmarkGoogle Scholar
- Sømme L (1996) Anhydrobiosis and cold tolerance in tardigrades. Eur J Entomol 93:349–357Google Scholar