Characterization and Phylogenetic Analysis of the Mitochondrial Genome of Glarea lozoyensis Indicates High Diversity within the Order Helotiales

Background

Glarea lozoyensis is a filamentous fungus used for the industrial production of non-ribosomal peptide pneumocandin B₀. In the scope of a whole genome sequencing the complete mitochondrial genome of the fungus has been assembled and annotated. It is the first one of the large polyphyletic Helotiaceae family. A phylogenetic analysis was performed based on conserved proteins of the oxidative phosphorylation system in mitochondrial genomes.

Results

The total size of the mitochondrial genome is 45,038 bp. It contains the expected 14 genes coding for proteins related to oxidative phosphorylation,two rRNA genes, six hypothetical proteins, three intronic genes of which two are homing endonucleases and a ribosomal protein rps3. Additionally there is a set of 33 tRNA genes. All genes are located on the same strand. Phylogenetic analyses based on concatenated mitochondrial protein sequences confirmed that G. lozoyensis belongs to the order of Helotiales and that it is most closely related to Phialocephala subalpina. However, a comparison with the three other mitochondrial genomes known from Helotialean species revealed remarkable differences in size, gene content and sequence. Moreover, it was found that the gene order found in P. subalpina and Sclerotinia sclerotiorum is not conserved in G. lozoyensis.

Conclusion

The arrangement of genes and other differences found between the mitochondrial genome of G. lozoyensis and those of other Helotiales indicates a broad genetic diversity within this large order. Further mitochondrial genomes are required in order to determine whether there is a continuous transition between the different forms of mitochondrial genomes or G. lozoyensis belongs to a distinct subgroup within Helotiales.