Linear Mitochondrial DNAs of Yeasts: Frequency of Occurrence and General Features

Abstract

In most yeast species, the mitochondrial DNA (mtDNA) has been reported to be a circular molecule. However, two cases of linear mtDNA with specific termini have previously been described. We examined the frequency of occurrence of linear forms of mtDNA among yeasts by pulsed-field gel electrophoresis. Among the 58 species from the genera Pichia and Williopsis that we examined, linear mtDNA was found with unexpectedly high frequency. Thirteen species contained a linear mtDNA, as confirmed by restriction mapping, and labeling, and electron microscopy. The mtDNAs from Pichia pijperi, Williopsis mrakii, and P. jadinii were studied in detail. In each case, the left and right terminal fragments shared homologous sequences. Between the terminal repeats, the order of mitochondrial genes was the same in all of the linear mtDNAs examined, despite a large variation of the genome size. This constancy of gene order is in contrast with the great variation of gene arrangement in circular mitochondrial genomes of yeasts. The coding sequences determined on several genes were highly homologous to those of the circular mtDNAs, suggesting that these two forms of mtDNA are not of distant origins.

Genome analysis of five recently described species of the CUG-Ser clade uncoversCandida theaeas a new hybrid lineage with pathogenic potential in theCandida parapsilosisspecies complex

“…in the families Debaryomycetaceae , Phaffomycetaceae , Pichiaceae , Saccharomycodaceae , Trichomonascaceae ) indicating their recurrent emergence in evolution presumably from closely related circular ancestors. 18 , 48 , 57 , 58 This conclusion is further supported by three different types of telomeric structures present at the ends of linear mitochondrial DNAs, i.e. covalently closed single-stranded hairpins (Type 1), arrays of tandem repeats (Type 2) and a protein covalently bound to the 5′ termini of DNA molecules (Type 3).…”

DNA sequences coding for the ribosomal small subunit RNA and valyl tRNA from the linear mitochondrial genome of the yeastWilliopsis mrakii

“…Mitochondrial DNA (mtDNA) of the yeast Williopsis mrakii (Hansenula mrakii, CBS 1707) is a linear molecule of 58 kilobase pairs, with an inverted repeat sequence at each end (1,2,3). In all the linear mtDNAs of yeast we have examined so far, the gene order seems to be strictly conserved, the ribosomal small subunit RNA (15S rRNA) gene being at the right end of the genome.…”