Institut Curie - Biologic, Centre Universitaire, Bâtiment 110, 91405, Orsay, France.
Curr Genet. 1982 Aug;5(3):191-7. doi: 10.1007/BF00391805.
The killer character of Kluyveromyces lactis is associated with a cytoplasmic genetic element which confers on the host cells: a) the capacity to kill sensitive cells of various yeast by producing a diffusible toxin, and b) the immunity to that toxin. The killing activity is associated with the presence of two linear DNA plasmids that we call kl and k2. Both plasmids seem to be required for the expression of the killing activity. Mutants defective for the killing activity have been isolated by mutagenesis and are either cytoplasmic or nuclear. Four classes of cytoplasmic mutations have been found: 1) loss of kl ; 2) loss of both k1 and k2; 3) internal deletion in kl and 4) probable point mutations in the plasmids. Among the nuclear mutants, many conserved the normal plasmids, but expression of the killer phenotype was blocked. In some respects, the organisation of this plasmid system resembles a DNA version of the double-stranded RNA killer system of Saccharomyces cerevisiae.
产朊假丝酵母的杀伤特性与其细胞质遗传因子有关，该因子使宿主细胞具有以下特性：a）通过产生可扩散毒素杀伤各种敏感酵母细胞的能力；b）对该毒素的免疫性。杀伤活性与两种线性 DNA 质粒的存在有关，我们称之为 kl 和 k2。这两种质粒似乎都需要表达杀伤活性。通过诱变已分离出杀伤活性缺陷的突变体，这些突变体要么是细胞质的，要么是核的。已经发现了四类细胞质突变：1）kl 的缺失；2）kl 和 k2 的同时缺失；3）kl 内缺失；4）质粒中的可能点突变。在核突变体中，许多保持了正常的质粒，但杀伤表型的表达被阻断。在某些方面，这个质粒系统的组织类似于酿酒酵母双链 RNA 杀伤系统的 DNA 版本。
