Short repetitive sequences in green algal mitochondrial genomes: potential roles in mitochondrial genome evolution |
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Authors: | Nedelcu AM; Lee RW |
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Institution: | Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada. amned@is2.dal.ca |
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Abstract: | Current data on green algal mitochondrial genomes suggest an unexpected
dichotomy within the group with respect to genome structure, organization,
and sequence affiliations. The present study suggests that there is a
correlation between this dichotomy on one hand and the differences in the
abundance, base composition, and distribution of short repetitive sequences
we observed among green algal mitochondrial genomes on the other. It is
conceivable that the accumulation of GC- rich short repeated sequences in
the Chlamydomonas-like but not Prototheca-like mitochondrial genomes might
have triggered evolutionary events responsible for the distinct series of
evolutionary changes undergone by the two green algal mitochondrial
lineages. The similarity in base composition, nucleotide sequence,
abundance, and mode of organization we observed between the short
repetitive sequences present in Chlamydomonas-like mitochondrial genomes on
one hand and fungal and vertebrate homologs on the other might extend to
some of the roles that the short repetitive sequences have been shown to
have in the latter. Potential involvements we propose for the short
repetitive sequences in the evolution of Chlamydomonas-like mitochondrial
genomes include fragmentation and scrambling of the ribosomal-RNA-coding
regions, extensive gene rearrangements, coding-region deletions, surrogate
origins of replication, and chromosomal linearization.
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