Stress response in tardigrades: differential gene expression of molecular chaperones

Abstract

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 (MtsHsp17.2 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.

Sequence analysis of the DNA-repair gene rad51 in the tardigrades Milnesium cf. tardigradum, Hypsibius dujardini and Macrobiotus cf. harmsworthi

“…tardigradum animals were isolated from culture in a Petri dish with 1 mL of sterile distilled water. DNA was extracted after two days of starvation to avoid extraction of contaminant RNA/DNA from food in the gut (Reuner et al, 2010). Animals were processed following the instructions from the GenElute™ Mammalian Total DNA Miniprep Kit (G1N70 Sigma).…”

Heat shock proteins and hypometabolism: adaptive strategy for proteome preservation

“…By contrast, only limited changes in hsp gene expression were associated with anhydrobiosis in a tardigrade species. 85 …”

Heat shock proteins in encysted and anhydrobiotic eutardigrades

“…In the moss-dwelling R. coronifer, desiccated animals exhibited a lower level of Hsp70 with respect to hydrated ones, with a clear induction of Hsp70 only one hour after rehydration of the animals (Jönsson, and Schill 2007). In another desiccation-tolerant eutardigrade, Milnesium tardigradum Doyère, 1840, only the gene transcript of one of the three detected hsp70 isoforms was significantly up-regulated in the transitional stage between active and anhydrobiotic stages (Schill et al 2004;Reuner et al 2009). In regard to Hsp90, our data on B. volubilis, are in line with those obtained by Rizzo et al (2010) on P. richtersi, and indicate that dehydration also does not induce an increase of Hsp90.…”