Production of reactive oxygen species and involvement of bioprotectants during anhydrobiosis in the tardigrade Paramacrobiotus spatialis

Water unavailability is an abiotic stress causing unfavourable conditions for life. Nevertheless, some
animals evolved anhydrobiosis, a strategy allowing for the reversible organism dehydration and
suspension of metabolism as a direct response to habitat desiccation. Anhydrobiotic animals undergo
biochemical changes synthesizing bioprotectants to help combat desiccation stresses. One stress
is the generation of reactive oxygen species (ROS). In this study, the eutardigrade Paramacrobiotus
spatialis was used to investigate the occurrence of ROS associated with the desiccation process.
We observed that the production of ROS signifcantly increases as a function of time spent in
anhydrobiosis and represents a direct demonstration of oxidative stress in tardigrades. The degree
of involvement of bioprotectants, including those combating ROS, in the P. spatialis was evaluated
by perturbing their gene functions using RNA interference and assessing the successful recovery
of animals after desiccation/rehydration. Targeting the glutathione peroxidase gene compromised
survival during drying and rehydration, providing evidence for the role of the gene in desiccation
tolerance. Targeting genes encoding glutathione reductase and catalase indicated that these
molecules play roles during rehydration. Our study also confrms the involvement of aquaporins 3 and
10 during rehydration. Therefore, desiccation tolerance depends on the synergistic action of many
diferent molecules working together.