Lethal and mutagenic effects of ion beams and γ-rays in Aspergillus oryzae

• Published in: Mutation research Vol. 740; no. 1-2; p. 43
• Main Authors: Toyoshima, Yoshiyuki, Takahashi, Akemi, Tanaka, Hisaki, Watanabe, Jun, Mogi, Yoshinobu, Yamazaki, Tatsuo, Hamada, Ryoko, Iwashita, Kazuhiro, Satoh, Katsuya, Narumi, Issay
• Format: Journal Article
• Language: English
• Published: Netherlands 01.12.2012
• Subjects: Aspergillus oryzae - radiation effects; Carbon; Cell Survival - radiation effects; Gamma Rays; Heavy Ions; Linear Energy Transfer; Mutagenesis; Mutation; Mutation Rate; Radiation, Ionizing
• ISSN: 0027-5107
• DOI: 10.1016/j.mrfmmm.2012.12.005

Aspergillus oryzae is a fungus that is used widely in traditional Japanese fermentation industries. In this study, the lethal and mutagenic effects of different linear energy transfer (LET) radiation in freeze-dried conidia of A. oryzae were investigated. The lethal effect, which was evaluated by a 90% lethal dose, was dependent on the LET value of the ionizing radiation. The most lethal ionizing radiation among that tested was (12)C(5+) ion beams with an LET of 121keV/μm. The (12)C(5+) ion beams had a 3.6-times higher lethal effect than low-LET (0.2keV/μm) γ-rays. The mutagenic effect was evaluated by the frequency of selenate resistant mutants. (12)C(6+) ion beams with an LET of 86keV/μm were the most effective in inducing selenate resistance. The mutant frequency following exposure to (12)C(6+) ion beams increased with an increase in dose and reached 3.47×10(-3) at 700Gy. In the dose range from 0 to 700Gy, (12)C(5+) ion beams were the second most effective in inducing selenate resistance, the mutant frequency of which reached a maximum peak (1.67×10(-3)) at 400Gy. To elucidate the characteristics of mutation induced by ionizing radiation, mutations in the sulphate permease gene (sB) and ATP sulfurylase gene (sC) loci, the loss of function of which results in a selenate resistant phenotype, were compared between (12)C(5+) ion beams and γ-rays. We detected all types of transversions and transitions. For frameshifts, the frequency of a +1 frameshift was the highest in all cases. Although the incidence of deletions >2bp was generally low, deletions >20bp were characteristic for (12)C(5+) ion beams. γ-rays had a tendency to generate mutants carrying a multitude of mutations in the same locus. Both forms of radiation also induced genome-wide large-scale mutations including chromosome rearrangements and large deletions. These results provide new basic insights into the mutation breeding of A. oryzae using ionizing radiation.