Tardigrade proteins: molecular tools in the phenomenon of anhydrobiosis

Abstract Tardigrada (water bears) are a group of small invertebrates known for their ability to survive extreme desiccation by entering an anhydrobiotic state. This state is characterized by the loss of ≤ 98% of body water, resulting in body shrinkage and almost complete cessation of metabolism. In anhydrobiosis, multiple mechanical and biochemical stress effects, such as protein denaturation and aggregation, DNA damage, formation of reactive oxygen species, membrane disintegration and degeneration of cellular compartments, are counteracted by various proteins. Although multiple studies of individual proteins and tardigrade proteomes have been conducted, our knowledge of tardigrade anhydrobiosis-related proteins has not yet been reviewed. To fill this gap, based on available papers, we present a review of all tardigrade proteins known to contribute to desiccation survival, including intrinsically disordered proteins, heat shock proteins and reactive oxygen species-scavenging enzymes. Although proteins are the major anhydrobiosis-related factors in tardigrades, many questions regarding the role of the tardigrade proteome in anhydrobiosis remain unanswered.