Abstract
Yeasts are leading model organisms for mitochondrial genome studies. The explosion of complete sequence of yeast mitochondrial (mt) genomes revealed a wide diversity of organization and structure between species. Recently, genome-wide polymorphism survey on the mt genome of isolates of a single species, Lachancea kluyveri, was also performed. To compare the mitochondrial genome evolution at two hierarchical levels: within and among closely related species, we focused on five species of the Lachancea genus, which are close relatives of L. kluyveri. Hence, we sequenced the complete mt genome of L. dasiensis, L. nothofagi, L. mirantina, L. fantastica and L. meyersii. The phylogeny of the Lachancea genus was explored using these data. Analysis of intra- and interspecific variability across the whole Lachancea genus led to the same conclusions regarding the mitochondrial genome evolution. These genomes exhibit a similar architecture and are completely syntenic. Nevertheless, genome sizes vary considerably because of the variations of the intergenic regions and the intron content, contributing to mitochondrial genome plasticity. The high variability of the intergenic regions stands in contrast to the high level of similarity of protein sequences. Quantification of the selective constraints clearly revealed that most of the mitochondrial genes are under purifying selection in the whole genus.
Highlights
Yeasts and more precisely the phylum of Hemiascomycetes have significantly contributed to have a better understanding of mitochondrial genome evolution of species spanning a broad distance
All genes are transcribed from one DNA strand. Such as the mtDNA of L. kluyveri and L. thermotolerans previously sequenced, this set of genes is composed of 8 protein-coding genes and 27 noncoding RNA genes [10], [2]
By contrast to several species distantly related to S. cerevisiae, mt genomes of the Lachancea genus do not encode the seven subunits of the NADH: ubiquinone oxidoreductase complex [20], [21]
Summary
Yeasts and more precisely the phylum of Hemiascomycetes have significantly contributed to have a better understanding of mitochondrial (mt) genome evolution of species spanning a broad distance. The complete mitochondrial genome sequence is available for more than 40 hemiascomycetous species, which are representative of different genera [1]. This ever-growing data represented an opportunity to have a deep insight into the mtDNA organization and the genome architecture variation from an evolutionary perspective in a whole phylum. To obtain a global view of the genetic variations occurring in the mtDNA within a species, we recently performed a genomewide polymorphism survey on the mt genome of 18 Lachancea kluyveri (formerly known as Saccharomyces kluyveri) isolates [2]. Selection was evaluated and the results clearly suggested that purifying selection purged most indels and non-synonymous differences from mitochondrial protein-coding genes
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