Schild D, Ananthaswamy H N, Mortimer R K
Genetics. 1981 Mar-Apr;97(3-4):551-62. doi: 10.1093/genetics/97.3-4.551.
A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an alpha alpha diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. Homothallism was excluded as a cause of the increase in ploidy; visual pedigree analysis of spore clones to about the 32-cell stage failed to reveal any zygotes, and haploids that diploidized retained their mating type. An extra round of meiotic DNA synthesis was also considered and excluded. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30 degrees, but did not occur at 23 degrees. Two cycles of sporulation and growth at 23 degrees resulted in haploids, which were shown to diploidize within 24 hr when grown at 30 degrees. Visual observation of the haploid cells incubated at 36 degrees revealed a cell-division-cycle phenotype characteristic of mutations that affect nuclear division; complementation analysis demonstrated that the mutation, cdc31-2, is allelic to cdc31-1, a mutation isolated by Hartwell et al. (1973) and characterized as causing a temperature-sensitive arrest during late nuclear division. The segregation of cdc31-2 in heterozygous diploids was 2:2 and characteristic of a noncentromere-linked gene.
已分离出酿酒酵母的一种隐性温度敏感突变体，并证明其会导致单倍体和二倍体的倍性增加。遗传分析表明，携带该突变的菌株是aa二倍体，尽管诱变剂N-甲基-N'-硝基-N-亚硝基胍是在a单倍体菌株上进行诱变的。当突变菌株与αα二倍体杂交，所得四倍体进行孢子形成时，通过遗传分析和DNA测量表明，该四倍体的一些减数分裂后代本身就是四倍体，而不是四倍体减数分裂预期的二倍体。对这些四倍体继续产生四倍体减数分裂后代的能力进行了四代跟踪。同宗配合被排除是倍性增加的原因；对孢子克隆进行约32细胞阶段的直观谱系分析未发现任何合子，并且二倍体化的单倍体保留了它们的交配型。还考虑并排除了一轮额外的减数分裂DNA合成。发现四倍体化与孢子形成温度无关，但取决于孢子的萌发温度和生长温度。当孢子在30℃萌发和生长时会发生倍性增加，但在23℃时不会发生。在23℃进行两轮孢子形成和生长产生单倍体，当在30℃生长时，这些单倍体在24小时内会二倍体化。对在36℃孵育的单倍体细胞进行直观观察，发现了影响核分裂的突变所特有的细胞分裂周期表型；互补分析表明，该突变体cdc31-2与Hartwell等人（1973年）分离出的、其特征为在核分裂后期导致温度敏感停滞的突变体cdc31-1等位。cdc31-2在杂合二倍体中的分离比例为2:2，是非着丝粒连锁基因的特征。
