Functional protein clusters and regulatory motifs in Hypsibius dujardini und Milnesium tardigradum

Functional protein clusters and regulatory motifs do not only mediate the unique adaptation of tardigrades against extreme temperature and other harsh environmental conditions, but are important markers to distinguish species and taxonomic units. We show here in detail results of our current comparison between Hypsibius dujardini and Milnesium tardigradum. We found 50 different clusters of sequence similar proteins between both tardigrades of which 10 are tardigrade specific. Proteins of other clusters are involved in DNA and protein protection and protection against oxidative stress. Heat shock proteins were found in both tardigrades. Several ones (hsp10, hsp60, hsp70, hsp90, small hsp) were only present in M. tardigradum. Further we investigate differences in their regulation. Additionally protective protein functions include aquaporins, DNA protection including Helicases, DNA repair (DNA J family), cold-shock like and specific membrane protection proteins. In functional terms the protein inventory of M. tardigradum and H. dujardini involves similar protein, DNA and stress protective functions. However, results indicate that both species have several specific and independent protein families for these tasks and more M. tardigradum-specific families became apparent from the ongoing sequencing project. Furthermore, the high resistance of M. tardigradum against environmental stress may result from the comprehensive capabilities of such species-specific families.