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

Abstract

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 (LD₂₀) 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.

Keywords::

• Chironomus ramosus
• alkaline comet assay
• gamma radiation stress
• DNA damage response
• Pulsed field gel electrophoresis
• dynamic light scattering

Acknowledgements

Authors thank Dr R.C. Chaubey and Dr H. N. Bhilwade for their help with microscopy and SCGE data analysis software. Dr R. Shashidhar for his help in PFGE experiments and Dr Lata Panicker for DLS analysis. Authors acknowledge use of all the facilities provided in Molecular Biology Division of the Bhabha Atomic Research Centre, Mumbai and Department of Zoology, University of Pune, for experimental work. This work was supported by University Grant Commission-Centre for Advance Studies (UGC-CAS), Department of Science and technology-Promotion of University Research and Scientific Excellence (DST-PURSE) and Department Research and Development Programme (DRDP). Support from Department of Atomic Energy (DAE), India, for fellowship to KDD and PG under BARC-UoP (Bhabha Atomic Research Centre-University of Pune) collaborative PhD programme (BBN and RM) is duly accredited.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.

Supplementary material available online

Supplementary Tables and Figures available online at http://informahealthcare.com/abs/doi/10.3109/09553002.2015.1021962