DeLange A M, Mishra N C
Mutat Res. 1982 Oct;96(2-3):187-99. doi: 10.1016/0027-5107(82)90086-0.
Several MMS-sensitive mutants of Neurospora crassa were compared with the wild-type strain for their relative sensitivities to UV, X-ray, and histidine. They were also compared for the frequency of spontaneous mutation at the loci which confer assistance to p-fluorophenylalanine. The mutants were also examined for possible defects in meiotic behavior in homozygous crosses and for any change in the inducible DNA salvage pathways (as indicated by their ability to utilize DNA as the sole phosphate source in the growth medium). On the basis of these characterizations, the present MMS-sensitive mutants of Neurospora can be placed into three groups. The first group includes three mutants, mus-(SC3), mus-(SC13), and mus-(SC28). These are slow growers, insensitive to histidine with no apparent meiotic defects and may have reduced frequency of spontaneous mutation. In addition, their mycelial growth is sensitive to MMS but the conidial viability following MMS, UV or X-ray treatment appears normal or only slightly more sensitive than the wild-type. The second group includes only one mutant, mus-(SC15); its mycelial growth is very sensitive to MMS but the conidial survival following treatment with MMS or UV appears normal; however, the conidial survival following exposure to X-ray is significantly reduced. This mutant shows an increased (more than 10-fold) frequency of spontaneous mutation, but behaves normal like the wild-type with respect to fertility, growth rate and insensitivity to histidine. The third group includes mutants mus-(SC10), mus-(SC25), and mus-(SC29). These mutants are very sensitive to UV, X-rays and MMS and to histidine but have normal growth rates on minimal medium. Mutant mus-(SC10), but not mus-(SC25) and mus-(SC29), has an increased (11 X) frequency of spontaneous mutation. On the basis of data presented, the MMS sensitivity of the first group of mutants cannot be ascertained to arise from a defect in the DNA repair pathways; instead, it may stem from altered cell permeability or other pleotropic effects of the mus mutations. However, it can be suggested that the second and third group of mus mutants may indeed result from a defect in the DNA repair pathways controlled by the mus genes; this conclusion is based on their cross-sensitivity to the number of DNA-damaging agents such as MMS, UV and/or X-ray, high frequencies of spontaneous mutation (mutator effects) and defects in meiotic behavior.
将粗糙脉孢菌的几个对甲基磺酸甲酯（MMS）敏感的突变体与野生型菌株在对紫外线、X射线和组氨酸的相对敏感性方面进行了比较。还比较了它们在赋予对对氟苯丙氨酸抗性的位点上的自发突变频率。对这些突变体在纯合杂交中的减数分裂行为可能存在的缺陷以及诱导性DNA挽救途径的任何变化（以它们在生长培养基中利用DNA作为唯一磷源的能力来表示）进行了检测。基于这些特征，目前粗糙脉孢菌的MMS敏感突变体可分为三组。第一组包括三个突变体，mus-(SC3)、mus-(SC13)和mus-(SC28)。这些是生长缓慢的菌株，对组氨酸不敏感，没有明显的减数分裂缺陷，并且自发突变频率可能降低。此外，它们的菌丝体生长对MMS敏感，但在MMS、紫外线或X射线处理后的分生孢子活力看起来正常，或者仅比野生型稍敏感一些。第二组仅包括一个突变体，mus-(SC15)；其菌丝体生长对MMS非常敏感，但在MMS或紫外线处理后的分生孢子存活率看起来正常；然而，在暴露于X射线后的分生孢子存活率显著降低。这个突变体显示出自发突变频率增加（超过10倍），但在育性、生长速率和对组氨酸不敏感方面表现得像野生型一样正常。第三组包括突变体mus-(SC10)、mus-(SC25)和mus-(SC29)。这些突变体对紫外线、X射线、MMS和组氨酸非常敏感，但在基本培养基上生长速率正常。突变体mus-(SC10)，但不是mus-(SC25)和mus-(SC29)，自发突变频率增加（11倍）。根据所呈现的数据，第一组突变体对MMS的敏感性不能确定是由DNA修复途径中的缺陷引起的；相反，它可能源于mus突变导致的细胞通透性改变或其他多效性效应。然而，可以推测第二组和第三组mus突变体可能确实是由mus基因控制的DNA修复途径中的缺陷导致的；这个结论是基于它们对诸如MMS、紫外线和/或X射线等多种DNA损伤剂的交叉敏感性、高自发突变频率（诱变效应）以及减数分裂行为中的缺陷得出的。
