Rayko E, Goursot R, Bernardi G
Laboratoire de Génétique Moléculaire, Institut Jacques Monod, Paris, France.
Gene. 1993 Oct 15;132(2):167-74. doi: 10.1016/0378-1119(93)90192-6.
Previous work from our laboratory showed that mitochondrial (mt) genomes, with tandem repeat units, from spontaneous, cytoplasmic petite mutants of Saccharomyces cerevisiae do not exhibit site-specific recombination in petite x petite crosses [Rayko et al., Gene 63 (1988) 213-226]. Here, we have extended and confirmed these observations by studying other crosses of petites with tandem repeat units, as well as crosses in which one of the parents was, instead, an unstable petite, a-15/4/1, having a palindromic mt genome. In no case was site-specific recombination of the parental mt genomes observed. Progeny cells harbored mt genomes derived from either one or both of the two parents, as shown by analysis of restriction fragments. In the case of biparental inheritance, extensive subcloning of the diploids showed that this was due to a persistent heteroplasmic state and not to intermolecular recombination. The 'new' restriction fragments present in the mt DNA from some diploids were shown to be derived from the unstable parental genome, a-15/4/1, by a secondary excision process. Lack of site-specific recombination is, therefore, not only a feature of crosses involving petite genomes made up of tandem repeat units, but also of crosses in which one parental genome consists of inverted repeats and frequently originates secondary petite genomes formed by tandem repeats. Previous reports of mt recombination in petite mutants are discussed in light of these results.
我们实验室之前的研究表明，来自酿酒酵母自发细胞质小菌落突变体的带有串联重复单元的线粒体（mt）基因组，在小菌落×小菌落杂交中不表现出位点特异性重组[Rayko等人，《基因》63（1988）213 - 226]。在这里，我们通过研究其他带有串联重复单元的小菌落杂交组合，以及其中一方亲本为不稳定小菌落a - 15/4/1（其线粒体基因组具有回文结构）的杂交组合，扩展并证实了这些观察结果。在任何情况下，均未观察到亲本线粒体基因组的位点特异性重组。通过对限制性片段的分析表明，子代细胞含有源自两个亲本之一或两者的线粒体基因组。在双亲遗传的情况下，对二倍体进行广泛的亚克隆表明，这是由于持续的异质性状态，而非分子间重组。一些二倍体线粒体DNA中存在的“新”限制性片段被证明是通过二次切除过程源自不稳定的亲本基因组a - 15/4/1。因此，缺乏位点特异性重组不仅是涉及由串联重复单元组成的小菌落基因组杂交的一个特征，也是其中一个亲本基因组由反向重复组成且经常产生由串联重复形成的次生小菌落基因组的杂交的一个特征。根据这些结果，对之前关于小菌落突变体中线粒体重组的报道进行了讨论。
