Meeting Abstract
Tardigrades make up a phylum of microscopic animals renowned for their ability to survive an array of extreme environmental stresses. The molecules tardigrades make protect themselves from the harmful effects of these environmental stresses have not been elucidated. To identify mediators of tardigrade stress tolerance, we sequenced and compared transcriptomes from tardigrades that had been frozen, desiccated, or left hydrated (unstressed). We found that members of a gene family that is unique to tardigrades are upregulated during desiccation, but not freezing. We found that these genes are required for tardigrades to robustly survive desiccation, and heterologous expression of these genes in yeast or bacteria increases their desiccation tolerance by up to two orders of magnitude. Furthermore, we found that the purified protein products of these genes can protect the structural and functional integrity of desiccation sensitive proteins in vitro. The proteins encoded by these genes are intrinsically disordered and lack a stable three-dimensional structure in dilute solution. We found that at high concentrations these proteins interact with one another, stabilizing transient secondary structures and facilitating formation of a reticular gel matrix. Upon desiccation, this gel does not crystallize, but rather forms a vitrified, glass-like, solid both in vivo and in vitro. The vitrified state appears to be mechanistically essential for protection because disrupting the glassiness results in a loss of desiccation tolerance in both tardigrades and heterologous systems. These data identify the first functional mediators of desiccation tolerance in tardigrades and provide insight into the mechanisms used by these animals to cope with the harmful effects of desiccation.
