The tardigrade Hypsibius exemplaris dramatically upregulates DNA repair pathway genes in response to ionizing radiation [IR_RNA-seq]
Tardigrades can survive remarkable doses of ionizing radiation, up to about 1000 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 damage is repaired. We show that this tardigrade 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 for tardigrade radiation tolerance. We hypothesize that tardigrades' ability to sense ionizing radiation and massively upregulate specific DNA repair pathway genes may represent an evolved solution for maintaining DNA integrity. Overall design: To identify genes that are enriched following ionizing radiation (IR) exposure, Hypsibius exemplaris were exposed to 0, 100, 500, or 2,180 Gy of IR. We then performed gene expression profiling analysis from data obtained from 3 replicates of each dose of IR and compared to the 0 Gy (not irradiated) samples