The vast majority of animal species do not tolerate severe water stress, but the encysted embryo of the brine shrimp Artemia franciscana is an exceptionally useful organism to investigate physiological mechanisms for enduring extreme environmental insults. Any substantial reduction in cellular water poses a threat to survival. Nevertheless anhydrobiotic animals survive virtually complete loss of cellular water. The mechanisms that govern "life without water" (anhydrobiosis) are still not well understood. With certain exceptions, it seems that a recurring strategy for tolerating severe water loss involves the accumulation of both low molecular weight solutes (e.g., trehalose or other polyol) and highly hydrophilic macromolecules such as late embryogenesis abundant (LEA) proteins, which were first described about 20 years ago in plant seeds. New studies show that LEA proteins found in animals not only protect proteins in the cytosol during desiccation, but also confer resistance to water stress, including freeze tolerance, to the mitochondrion.
Keywords: drying; freezing; late embryogenesis abundant; mitochondria; stress tolerance; targeting sequence.