1022-7954/02/3806- $27.00 © 2002
Russian Journal of Genetics, Vol. 38, No. 6, 2002, pp. 642–655. Translated from Genetika, Vol. 38, No. 6, 2002, pp. 773–788.
Original Russian Text Copyright © 2002 by Odintsova, Yurina.
Mitochondrial genomes of various organisms differ
in size, gene content, and organization. At present, the
total primary structures of mitochondrial genomes of
many eukaryotes, mainly animals, have been estab-
lished. In this regard, the phyla Chordata (including
) and Arthropoda have been investigated
in most detail. Complete sequences of mtDNA were
obtained for about 150 animal species
. Far less is
known about the mitochondrial genomes of other rep-
resentatives of the kingdom Eukarya (see OGMP data-
base, Organelle Genome Megasequencing Program):
By convention, mitochondrial genomes can be
divided in two major groups. Mitochondria of animals,
ﬂagellates, and fungi have comparatively small and
compact genomes, from 16–19 kb in animals to 170–
176 kb in some fungi. In mitochondria of these organ-
isms, the modiﬁed genetic code is used. Mitochondrial
genomes of higher plants are much larger: from 200 to
2400 kb. They are less compact and contain long spac-
ers. In these genomes, the universal genetic code is
used [1, 2]. Mitochondrial genomes of parasitic proto-
zoans of the phylum Apicomplexa (
consist of DNA minicir-
cles of 6–7 kb in size [3, 4]. The sizes of minicircular
kinetoplast DNA in species of the family Trypanoso-
matidae vary from 0.47 to 9.2 kb .
Comparison of total nucleotide sequences of mito-
chondrial DNA (mtDNA) of organisms from various
taxonomic groups is necessary in order to understand
the origin of that great mitochondrial genome diversity.
In this review, data reported until the second half of the year 2000
Here and in what follows, taxonomic names follow those pre-
sented in the papers cited.
This would provide answers to question which genes
are present in a certain genome, how they are arranged,
whether they have introns, how spacers are distributed
throughout the genome and how long they are, whether
repetitive sequences are present in the genome, etc.
Based on this evidence, the common ancestor mito-
chondrial genome and its subsequent evolution can be
deduced. Analysis of mtDNAs of primitive organisms,
such as protists, is of special interest. Protists are a large
biologically diverse group of unicellular eukaryotes.
They include Protozoa and microscopic algae
group diverged from more complex plants, fungi, and
animals at early evolutionary stages and formed an
individual phylogenetic branch.
In this review, we present data on the structure and
function of mitochondrial genomes of three protist
groups: Protozoa and unicellular red and green aglae.
At present, mitochondrial genomes of many organ-
isms have been completely or partially sequenced
(Table 1). Their sequences indicate that the structure
and content of their genes, as well as organization of the
mitochondrial genomes in this group are more diverse
than in multicellular eukaryotes. The genome includes
covalently closed circular and linear DNA molecules;
the circular form is predominant (Table 1). In gene
composition, mtDNAs of protists are closer to those
plants than of animals or fungi. Of all mtDNAs, the
greatest number of genes have been identiﬁed in the
Other sequenced mtDNAs contain only part of the
genes. It is suggested that the set of
Henderson’s Dictionary of Biological Terms, Lawrence, E., Ed.,
New York: John Wiley and Sons, 1995.
The Mitochondrial Genome of Protists
M. S. Odintsova and N. P. Yurina
Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, 119071 Russia;
fax: (095) 954-27-32; e-mail: email@example.com
Received August 14, 2001
—The data on the structure and functions of the mitochondrial genomes of protists (Protozoa and uni-
cellular red and green algae) are reviewed. It is emphasized that mitochondrial gene structure and composition,
as well as organization of mitochondrial genomes in protists are more diverse than in multicellular eukaryotes.
The gene content of mitochondrial genomes of protists are closer to those of plants than animals or fungi. In
the protist mitochondrial DNA, both the universal (as in higher plants) and modiﬁed (as in animals and fungi)
genetic codes are used. In the overwhelming majority of cases, protist mitochondrial genomes code for the
major and minor rRNA components, some tRNAs, and about 30 proteins of the respiratory chain and ribo-
somes. Based on comparison of the mitochondrial genomes of various protists, the origin and evolution of mito-
chondria are brieﬂy discussed.