The distribution of optional mitochondrial introns encoding putative homing endonuclease genes in the Fusarium oxysporum complex

Cunnington J. H. (2009) The distribution of optional mitochondrial introns encoding putative homing endonuclease genes in the Fusarium oxysporum complex.

Sydowia 61 (1): 1–9

To determine if optional introns are responsible for size variation in the Fusarium oxysporum mitochondrial genome, the distribution of introns in five genes was determined for 16 isolates. Introns were found in two genes. These introns contained open reading frames coding for putative homing endonuclease genes. A homing endonuclease gene containing two LAGLIDADG motifs was present in an intron in the NADH ubiquinone oxidoreductase subunit 5 gene of all isolates. Nine isolates had a homing endonuclease gene with a GIY-YIG motif in an intron in the apocytochrome b (cob) gene. A second intron containing a LAGLIDADG homing endonuclease gene was found in the cob gene of two isolates. Phylogenetic analysis of the isolates based on partial translation elongation factor 1-alpha gene intron sequences revealed a relationship between evolutionary history and homing endonuclease gene distribution in the cob gene. The absence, or presence of one or two homing endonuclease genes in the cob gene, correlated with previously reported F. oxysporum clades 2, 3, and 1, respectively. This information could be used to help delimit subspecific taxa in the F. oxysporum complex.

Keywords: mitochondrial genomics, Hypocreales, phylogeny