Publication Date:
2024-05-24
Description:
Mitochondria originated from an ancient bacterial endosymbiont that
underwent reductive evolution by gene loss and endosymbiont gene transfer to the nuclear
genome. The diversity of mitochondrial genomes published to date has revealed
that gene loss and transfer processes are ongoing in many lineages. Most well-studied
eukaryotic lineages are represented in mitochondrial genome databases, except for the
superphylum Retaria—the lineage comprising Foraminifera and Radiolaria. Using singlecell
approaches, we determined two complete mitochondrial genomes of Foraminifera
and two nearly complete mitochondrial genomes of radiolarians. We report the complete
coding content of an additional 14 foram species. We show that foraminiferan
and radiolarian mitochondrial genomes contain a nearly fully overlapping but reduced
mitochondrial gene complement compared to other sequenced rhizarians. In contrast to
animals and fungi, many protists encode a diverse set of proteins on their mitochondrial
genomes, including several ribosomal genes; however, some aerobic eukaryotic lineages
(euglenids, myzozoans, and chlamydomonas-like algae) have reduced mitochondrial
gene content and lack all ribosomal genes. Similar to these reduced outliers, we show
that retarian mitochondrial genomes lack ribosomal protein and tRNA genes, contain
truncated and divergent small and large rRNA genes, and contain only 14 or 15 proteincoding
genes, including nad1, -3, -4, -4L, -5, and -7, cob, cox1, -2, and -3, and atp1, -6,
and -9, with forams and radiolarians additionally carrying nad2 and nad6, respectively. In
radiolarian mitogenomes, a noncanonical genetic code was identified in which all three
stop codons encode amino acids. Collectively, these results add to our understanding of
mitochondrial genome evolution and fill in one of the last major gaps in mitochondrial
sequence databases.
Keywords:
Foraminifera
;
mitochondrial evolution
;
mitochondrial genome
;
Radiolaria
;
Retaria
;
Rhizaria
Repository Name:
National Museum of Natural History, Netherlands
Type:
info:eu-repo/semantics/article
Format:
application/pdf
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