A mobile group II intron of a naturally occurring rearranged mitochondrial genome in Kluyveromyces lactis.

Mitochondrial intron content is variable in the yeast Kluyveromyces lactis. Strains can be divided into three classes depending on the structure of the cytochrome oxidase subunit 1 (COX1) gene: (1) those containing intron K1 cox1.1, (2) those containing K1 cox1.2, 3 and 4 and, (3) those that contain all four introns. In addition, strains belonging to the first class (designated Type B strains), have an altered mitochondrial gene order relative to strains from classes (2) and (3) (Type A, Hardy et al. 1989). Crossing experiments reveal that K1 cox1.1 (a group II intron) transfers at high frequency (89%) to mitochondrial genomes lacking this intron. By contrast, the mobility of the remaining introns (all group I) is of the order of 7%.