Chironomus ramosus larvae exhibit DNA damage control in response to gamma radiation.

Purpose: Chironomus ramosus is one of the recently reported radiotolerant insects. Salivary gland cells of fourth instar larvae respond to ionizing radiations with increases in the levels of antioxidant enzymes and chaperone proteins. Here we made an attempt to study the state of nuclear DNA after exposure of larvae to a lethal dose for 20% of the population (LD(20)) of gamma radiation (2200 Gy, at a dose rate 5.5 Gy/min).

Materials And Methods: Genomic DNA preparations were subjected to competitive ELISA (Enzyme linked immunosorbent assay) for detection of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and dynamic light scattering (DLS) to monitor any radiation-induced damage. Single salivary gland cells were subjected to alkaline single cell gel electrophoresis (ASCGE), comet assay and pulsed field gel electrophoresis (PFGE) to check for DNA double-strand breaks.

Results: Results from all four experimental procedures confirmed damage of nucleobases and fragmentation of nuclear DNA immediately after radiation. Some 48 h after radiation exposure, modified 8-oxodG residues returned to basal level, homodispersity of genomic DNA reappeared, the length of comet tail regressed significantly (ASCGE) and PFGE pattern matched with that of high molecular weight unirradiated DNA.

Conclusion: Chironomus ramosus larvae showed control of DNA damage as observed over 48 h in post irradiation recovery which could be attributed to their ability to tolerate gamma radiation stress.