A mutation that permits the expression of normally silent copies of mating-type information in Saccharomyces cerevisiae.
A mutation that permits the expression of normally silent copies of mating-type information in Saccharomyces cerevisiae.
复制标题
一种突变，允许在酿酒酵母中表达通常沉默的交配型信息副本。
作者：
James E. Haber;Jeanne P. George
对酿酒酵母异宗和同宗菌株的研究表明，交配型信息位于 3 号染色体上的三个不同位点，尽管仅表达交配型 (MAT) 位点的信息（Hicks、Strathern 和 Herskowitz，1977）。我们发现隐性突变 cmt 允许在 HMa 和 HM α 基因座表达通常沉默的交配型信息副本。在携带 HMa 和 HM α 的单倍体菌株中，cmt 突变允许同时表达 α 和 α 信息，导致非交配（“MATa/MAT α”）表型。 cmt 的影响可以通过改变 HMa 或 HM alpha 的交配类型信息来掩盖。例如，基因型MATa hma HM alpha cmt的细胞具有a交配型，而MAT alpha hma HM alpha cmt菌株是非交配型。 HM 基因座上交配型信息的表达可以纠正 mata* 和 mat alpha 10 等位基因的交配和孢子形成缺陷。从携带 mat 突变的 cmt/cmt 二倍体中回收的减数分裂分离子表明，这些突变体并未“治愈”为正常 MAT 等位基因，正如使用同宗基因 HO 的平行研究中的情况一样。所有结果都与 HMa 和 hm α 等位基因均编码 α 信息，而 HM α 和 hma 均编码信息的观点一致。 cmt 突变表明，这些通常沉默的交配型和孢子形成信息副本可以表达，并且这些基因座的信息在功能上与 MAT 中发现的信息相同。 cmt 突变不会导致 MAT 处交配型等位基因的相互转化，并且与 MAT、HMa、HM α 或 HO 没有遗传关联。在 cmt 杂合子中，当 MAT 基因座处的基因型为 mata*/MAT alpha 或 mat alpha 10/MATa 时，cmt 变为纯合的频率大于 1%。
Studies of heterothallic and homothallic strains of Saccharomyces cerevisiae have led to the suggestion that mating-type information is located at three distinct sites on chromosome 3, although only information at the mating-type (MAT) locus is expressed (Hicks, Strathern and Herskowitz, 1977). We have found that the recessive mutation cmt permits expression of the normally silent copies of mating-type information at the HMa and HM alpha loci. In haploid strains carrying HMa and HM alpha, the cmt mutation allows the simultaneous expression of both a and alpha information, leading to a nonmating ("MATa/MAT alpha") phenotype. The effects of cmt can be masked by changing the mating-type information at HMa or HM alpha. For example, a cell of genotype MATa hma HM alpha cmt has an a mating type, while a MAT alpha hma HM alpha cmt strain is nonmating. Expression of mating-type information at the HM loci can correct the mating and sporulation defects of the mata* and mat alpha 10 alleles. Meiotic segregants recovered from cmt/cmt diploids carrying the mat mutations demonstrate that these mutants are not "healed" to normal MAT alleles, as is the case in parallel studies using the homothallism gene HO.--All of the results are consistent with the notion that the HMa and hm alpha alleles both code for alpha information, while HM alpha and hma both code for a information. The cmt mutation demonstrates that these normally silent copies of mating-type and sporulation information can be expressed and that the information at these loci is functionally equivalent to that found at MAT. The cmt mutation does not cause interconversions of mating-type alleles at MAT, and it is not genetically linked to MAT, HMa, HM alpha or HO. In cmt heterozygotes, cmt becomes homozygous at a frequency greater than 1% when the genotype at the MAT locus is mata*/MAT alpha or mat alpha 10/MATa.