Distribution of mitochondrial introns in the species Schizosaccharomyces pombe and the origin of the group II intron in the gene encoding apocytochrome b

Abstract

The mitochondrial genome size of 26 different Schizosaccharomyces pombe strains varies between 17.6 and 24.6 kilobase pairs due to the presence or absence of introns. One of these is the group II intron in the gene encoding apocytochrome b (cob: intron cobI1). Partial DNA sequences of continuous cob genes from six strains (including strain EF1: Trinkl et al. 1985) revealed identical nucleotide sequence in the region where the group II intron is inserted in the mosaic form of the gene. In contrast, analysis of the mosaic cob gene in strain UCD-FstI revealed several base pair changes in the exon regions flanking the splice point, compared with the continuous genes and with the mosaic cob gene in strain 50 (Lang et al. 1985). The base pair differences between the exons of the two mosaic cob genes and the identity of exons in all continuous cob genes argue in favour of the two cob introns in strains 50 and UCD-FstI as independent later acquisitions of the genes, rather than loss of the intron from a common mosaic ancestor of all strains. Other introns present in some but not all strain include two group I introns without open reading frame in the gene encoding subunit 1 of cytochrome c oxidase (cox1: introns cox1I2a and cox1I3), and two group I introns with open reading frames in the same gene (introns cox1I1 and cox1I2b).

Adenylyl cyclase activity of the fission yeast Schizosaccharomyces pombe is not regulated by guanyl nucleotides

“…Yeast strains and growing conditions S. pombe strains used were isolated independently from each other and are described in detail by Zimmer et al [38]. Briefly, strain 972 414 leul-32h-was isolated from grape juice in Switzerland and together with strain 975h+ is a parent of mutants comprising the 'Leupoldcollection'.…”

A low copy number central sequence with strict symmetry and unusual chromatin structure in fission yeast centromere.

“…S. pombe variant strains 267 (UCD-FSTI; isolated in Australia) and 270 (CBS5680; isolated in Poland) were described in Zimmer et al, (1987) and Levin et al (1990). We also used five other S. pombe wild-type strains (EF4, 0208, 0209, CSIR Y-830, NCYC132) (Zimmer et al, 1987) for genomic Southern hybridization probed with pRS138, pKT1 10, pKT104, and pSS163 (see Figure 1(b)). Intense hybridization bands were obtained, suggesting that these natural variants also contain centromeres similar to those reported here.…”

Phylogenetic evidence for horizontal transfer of an intervening sequence between species in a spirochete genus

“…Some of the best examples are the transfer of antibiotic resistance genes on plasmids or transposons in bacteria (14) and the movement of retroelements (29). Other good examples include group I and II introns that seem to have moved between species by horizontal transfer, on the basis of remarkable similarities in sequence in divergent organisms (2,4,10,15,16,18,19,31).…”