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Open Access Research article

Evidence for inter-specific recombination among the mitochondrial genomes of Fusarium species in the Gibberella fujikuroi complex

Gerda Fourie1*, Nicolaas A van der Merwe2, Brenda D Wingfield2, Mesfin Bogale2, Bettina Tudzynski3, Michael J Wingfield1 and Emma T Steenkamp1

Author Affiliations

1 Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa

2 Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa

3 University of Munster, Germany

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BMC Genomics 2013, 14:605  doi:10.1186/1471-2164-14-605

Published: 8 September 2013

Abstract

Background

The availability of mitochondrial genomes has allowed for the resolution of numerous questions regarding the evolutionary history of fungi and other eukaryotes. In the Gibberella fujikuroi species complex, the exact relationships among the so-called “African”, “Asian” and “American” Clades remain largely unresolved, irrespective of the markers employed. In this study, we considered the feasibility of using mitochondrial genes to infer the phylogenetic relationships among Fusarium species in this complex. The mitochondrial genomes of representatives of the three Clades (Fusarium circinatum, F. verticillioides and F. fujikuroi) were characterized and we determined whether or not the mitochondrial genomes of these fungi have value in resolving the higher level evolutionary relationships in the complex.

Results

Overall, the mitochondrial genomes of the three species displayed a high degree of synteny, with all the genes (protein coding genes, unique ORFs, ribosomal RNA and tRNA genes) in identical order and orientation, as well as introns that share similar positions within genes. The intergenic regions and introns generally contributed significantly to the size differences and diversity observed among these genomes. Phylogenetic analysis of the concatenated protein-coding dataset separated members of the Gibberella fujikuroi complex from other Fusarium species and suggested that F. fujikuroi (“Asian” Clade) is basal in the complex. However, individual mitochondrial gene trees were largely incongruent with one another and with the concatenated gene tree, because six distinct phylogenetic trees were recovered from the various single gene datasets.

Conclusion

The mitochondrial genomes of Fusarium species in the Gibberella fujikuroi complex are remarkably similar to those of the previously characterized Fusarium species and Sordariomycetes. Despite apparently representing a single replicative unit, all of the genes encoded on the mitochondrial genomes of these fungi do not share the same evolutionary history. This incongruence could be due to biased selection on some genes or recombination among mitochondrial genomes. The results thus suggest that the use of individual mitochondrial genes for phylogenetic inference could mask the true relationships between species in this complex.

Keywords:
Synteny; Group I intron; LAGLIDADG and GIY-YIG homing endonucleases; Incongruent phylogenies