Gather before dry up! Tardigrade protein self-assembles into fibrous condensates under desiccation condition

Tardigrades, also known as water bears or moss piglets, are unique microscopic animals that enter cryptobiotic states upon desiccation and thereby survive in extreme conditions, including radiation, air deprivation, and even exposure to space vacuum. Therefore, tardigrades have attracted the attention of many researchers attempting to unravel their cryptobiotic mechanisms, which remain mostly elusive. The collaborative groups in Japan, including researchers at Exploratory Research Center on Life and Living Systems (ExCELLS) of National Institutes of Natural Sciences, observed changes in molecular behaviors of a heat-soluble protein abundant in tardigrade cytosols (called CAHS1 protein). Their integrative spectroscopic and microscopic data demonstrate that the protein self-assembles into fibrous condensates under desiccation-mimicking conditions in a reversible manner. This dynamic protein organization suggests multistep anhydrobiotic mechanisms, including the reversible formation of protective compartments for desiccation-sensitive biomolecules, water-holding gelation, and maintenance of the integrity of biomolecular complexes under extremely dry conditions. These findings illustrate an adaptation strategy of organisms to extreme environments without water.