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Lethal and mutagenic effects of ion beams and $$gamma$$-rays in ${it Aspergillus oryzae}$

麹菌におけるイオンビームと$$gamma$$線の致死効果と変異誘発効果

豊島 快幸*; 高橋 明珠*; 田中 寿基*; 渡部 潤*; 茂木 喜信*; 山崎 達雄*; 濱田 涼子*; 岩下 和裕*; 佐藤 勝也; 鳴海 一成

Toyoshima, Yoshiyuki*; Takahashi, Akemi*; Tanaka, Hisaki*; Watanabe, Jun*; Mogi, Yoshinobu*; Yamazaki, Tatsuo*; Hamada, Ryoko*; Iwashita, Kazuhiro*; Sato, Katsuya; Narumi, Issei

${it Aspergillus oryzae}$ 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 ${it A. oryzae}$ 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 121 keV/$$mu$$m. The $$^{12}$$C$$^{5+}$$ ion beams had a 3.6-times higher lethal effect than low-LET (0.2 keV/$$mu$$m) $$gamma$$-rays. The mutagenic effect was evaluated by the frequency of selenate resistant mutants. $$^{12}$$C$$^{6+}$$ ion beams with an LET of 86 keV/$$mu$$m 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 $$times$$ 10$$^{-3}$$ at 700 Gy. In the dose range from 0 to 700 Gy, $$^{12}$$C$$^{5+}$$ ion beams were the second most effective in inducing selenate resistance, the mutant frequency of which reached a maximum peak (1.67 $$times$$ 10$$^{-3}$$) at 400 Gy. To elucidate the characteristics of mutation induced by ionizing radiation, mutations in the sulphate permease gene (${it sB}$) and ATP sulfurylase gene (${it sC}$) loci, the loss of function of which results in a selenate resistant phenotype, were compared between $$^{12}$$C$$^{5+}$$ ion beams and $$gamma$$-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 $$>$$ 2 bp was generally low, deletions $$>$$ 20 bp were characteristic for $$^{12}$$C$$^{5+}$$ ion beams. $$gamma$$-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.

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パーセンタイル:55.51

分野:Biotechnology & Applied Microbiology

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