Halibut mitochondrial genomes contain extensive heteroplasmic tandem repeat arrays involved in DNA recombination.
BACKGROUND
Halibuts are commercially important flatfish species confined to the North Pacific and North Atlantic Oceans. We have determined the complete mitochondrial genome sequences of four specimens each of Atlantic halibut (Hippoglossus hippoglossus), Pacific halibut (Hippoglossus stenolepis) and Greenland halibut (Reinhardtius hippoglossoides), and assessed the nucleotide variability within and between species.


RESULTS
About 100 variable positions were identified within the four specimens in each halibut species, with the control regions as the most variable parts of the genomes (10 times that of the mitochondrial ribosomal DNA). Due to tandem repeat arrays, the control regions have unusually large sizes compared to most vertebrate mtDNAs. The arrays are highly heteroplasmic in size and consist mainly of different variants of a 61-bp motif. Halibut mitochondrial genomes lacking arrays were also detected.


CONCLUSIONS
The complexity, distribution, and biological role of the heteroplasmic tandem repeat arrays in halibut mitochondrial control regions are discussed. We conclude that the most plausible explanation for array maintenance includes both the slipped-strand mispairing and DNA recombination mechanisms.
Mjelle
Kenneth A
KA
Department of Fisheries and Natural Sciences, Bodø University College, N-8049 Bodø, Norway. kenmjelle@hotmail.com
Karlsen
Bård O
BO
Jørgensen
Tor E
TE
Moum
Truls
T
Johansen
Steinar D
SD
D000818:Animals; D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics*; D005432:Flounder / Q000235:genetics*; D014644:Genetic Variation; D006239:Haplotypes / Q000235:genetics; D019901:Locus Control Region / Q000235:genetics; D008969:Molecular Sequence Data; D011995:Recombination, Genetic / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D020080:Tandem Repeat Sequences / Q000235:genetics*
D004272:DNA, Mitochondrial