The tardigrade Hypsibius exemplaris dramatically upregulates DNA repair pathway genes in response to ionizing radiation

Tardigrades can survive remarkable doses of ionizing radiation, up to about 1,000 times the lethal dose for humans. How they do so is incompletely understood. We found that the tardigrade Hypsibius exemplaris suffers DNA damage upon gamma irradiation, but the damage is repaired. We show that this species has a specific and robust response to ionizing radiation: irradiation induces a rapid upregulation of many DNA repair genes. This upregulation is unexpectedly extreme—making some DNA repair transcripts among the most abundant transcripts in the animal. By expressing tardigrade genes in bacteria, we validate that increased expression of some repair genes can suffice to increase radiation tolerance. We show that at least one such gene is important in vivo for tardigrade radiation tolerance. We hypothesize that the tardigrades’ ability to sense ionizing radiation and massively upregulate specific DNA repair pathway genes may represent an evolved solution for maintaining DNA integrity. •H. exemplaris incurs DNA damage from ionizing radiation and subsequently repairs the damage•Irradiation causes H. exemplaris to dramatically upregulate certain DNA repair genes•Expressing some tardigrade DNA repair genes in bacteria can protect against radiation•At least one upregulated gene contributes to H. exemplaris radiation tolerance Clark-Hachtel et al. investigate how tardigrades survive high doses of ionizing radiation and discover that the tardigrade Hypsibius exemplaris dramatically upregulates DNA repair genes in response to radiation. This regulation of DNA repair pathway genes may represent an evolved solution for maintaining DNA integrity under genotoxic stress.