Wagner E D, Plewa M J
Environ Mutagen. 1985;7(6):821-32. doi: 10.1002/em.2860070604.
A standard protocol for a micronucleus assay in root tips of Zea mays was developed and calibrated using 137Cs gamma radiation, ethylmethanesulfonate (EMS), and N-ethyl-N-nitrosourea (ENU). The root tips were sampled 1, 3, and 5 days after the treatment period. Primary root tips (sampled 1 day after treatment) were the most responsive with the highest frequencies of micronuclei. The frequencies then decreased to control values after 3 days. By treating the same kernels for this assay and the yellow-green-2 (yg2) forward mutation assay, it was possible to analyze and compare the induction kinetics of micronuclei formation in root-tip cells and forward mutation at the yg2 locus in leaf primordial cells. Forward mutation at the yg2 locus by gamma rays, EMS, or ENU exhibited one hit kinetics. The induction of micronuclei demonstrated nonlinear kinetics with a significant increase over controls above 200 rads gamma rays, 10 mM EMS, or 250 microM ENU. ENU induced a higher frequency of micronuclei at all treatment concentrations than did gamma radiation or EMS. The data suggest that a higher relative proportion of yg2 mutant sectors induced by ENU may be due to chromosome aberrations than those induced by gamma radiation or EMS.
开发了一种用于玉米根尖微核试验的标准方案，并使用137Cs伽马辐射、甲基磺酸乙酯（EMS）和N-乙基-N-亚硝基脲（ENU）进行了校准。在处理期后的第1、3和5天对根尖进行采样。主根尖（处理后1天采样）反应最灵敏，微核频率最高。3天后频率降至对照值。通过对用于该试验的相同籽粒以及黄绿-2（yg2）正向突变试验进行处理，可以分析和比较根尖细胞中微核形成的诱导动力学以及叶原基细胞中yg2位点的正向突变。伽马射线、EMS或ENU在yg2位点的正向突变表现出单 hit 动力学。微核的诱导表现出非线性动力学，在高于200拉德伽马射线、10 mM EMS或250 microM ENU时，相对于对照有显著增加。在所有处理浓度下，ENU诱导的微核频率均高于伽马辐射或EMS。数据表明，与伽马辐射或EMS诱导的相比，ENU诱导的yg2突变区段相对比例更高可能是由于染色体畸变。
