Hieda K
Mutat Res. 1981 Nov;84(1):17-27. doi: 10.1016/0027-5107(81)90046-4.
It was investigated whether there was a critical degree of dryness for induction of genetic changes by drying. Saccharomyces cerevisiae cells were dried in air of 0, 33, 53 and 76% relative humidity (RH). The frequencies of mitotic recombination at ade2, of gene conversion at leu1, and of gene mutation at can1 were measured in X2447, XS1473 and S288C strains, respectively. After the cells had been dried at 0% RH for 4 h the frequencies of the genetic changes at ade2, leu1 and can1 were, respectively, 56, 7 and 3.5 times higher than each spontaneous frequency. Induction rates, defined as the frequencies of the induced genetic changes per unit time (1 h) of drying, were greatly decreased with increase in RH. Partial drying in air of 76% RH up to 4 and 8 h induced no genetic change at ade2 and leu1, respectively. It was concluded, therefore, that drying at a certain RH between 53 and 76% gave the critical degree of dryness of cells for the induction of the genetic changes. The water contents of cells (g water per g dry material) were 12% at 53% RH and 21% at 76% RH, whereas the water content of native cells was 212%. Removal of a large amount of cellular water had no effect on the induction of the genetic changes. UV sensitivity of partially dried cells of X2447 for the induction of the genetic change at ade2 drastically increased with decrease in RH between 76 and 53%. The drastic change in the UV sensitivity suggested that photochemical reactivity of DNA of chromosome XV, in which the ade2 locus is located, changed between 76 and 53% RH. It seems that the genetic changes were induced only in the low RH region where DNA in vivo had a different photochemical reactivity.
研究了干燥诱导遗传变化是否存在临界干燥程度。将酿酒酵母细胞在相对湿度（RH）为0%、33%、53%和76%的空气中干燥。分别在X2447、XS1473和S288C菌株中测量了ade2位点的有丝分裂重组频率、leu1位点的基因转换频率和can1位点的基因突变频率。当细胞在0%RH下干燥4小时后，ade2、leu1和can1位点的遗传变化频率分别比各自的自发频率高56倍、7倍和3.5倍。诱导率定义为每单位干燥时间（1小时）诱导的遗传变化频率，随着RH的增加而大大降低。在76%RH的空气中部分干燥4小时和8小时，分别在ade2和leu1位点未诱导出遗传变化。因此得出结论，在53%至76%之间的某个RH下干燥会使细胞达到诱导遗传变化的临界干燥程度。细胞的含水量（每克干物质中的水克数）在53%RH时为12%，在76%RH时为21%，而天然细胞的含水量为212%。去除大量细胞内水分对遗传变化的诱导没有影响。X2447部分干燥细胞对ade2位点遗传变化诱导的紫外线敏感性随着RH在76%至53%之间的降低而急剧增加。紫外线敏感性的急剧变化表明，位于第XV号染色体上的ade2基因座的DNA光化学反应性在76%至53%RH之间发生了变化。似乎遗传变化仅在体内DNA具有不同光化学反应性的低RH区域被诱导。
