Mitochondrion is a key evolutionary inventions specific to the eukaryotic cell.
Oxymonads remained as one of a few eukaryotic groups, where no
mitochondrion has been revealed so far. We have performed detailed genomic
and transcriptomic study of oxymonad Monocercomonoides sp., which
demonstrates the absence of mitochondrial hallmark proteins. The most
striking is the absence of canonical mitochondrial protein import machinery and
the substitution of mitochondrial iron sulphur cluster biosynthetic pathway
(ISC) by the sulphur mobilization system (SUF). We conclude that
Monocercomonoides represents the first report of amitochondriate eukaryote
demonstrating the fact that under some circumstances eukaryotes may entirely
loose mitochondrion.
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