Phylogenetic Affinity of Mitochondria of Euglena gracilis and Kinetoplastids Using Cytochrome Oxidase I and hsp60 |
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Authors: | Shinji Yasuhira Larry Simpson |
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Institution: | (1) Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095-1662, USA, US;(2) Department of Molecular, Cellular and Developmental Biology, University of California, Los Angeles, CA 90095-1662, USA, US;(3) Department of Medical Microbiology and Immunology, University of California, Los Angeles, CA 90095–1662, USA, US |
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Abstract: | The mitochondrial DNA-encoded cytochrome oxidase subunit I (COI) gene and the nuclear DNA-encoded hsp60 gene from the euglenoid
protozoan Euglena gracilis were cloned and sequenced. The COI sequence represents the first example of a mitochondrial genome-encoded gene from this
organism. This gene contains seven TGG tryptophan codons and no TGA tryptophan codons, suggesting the use of the universal
genetic code. This differs from the situation in the mitochondrion of the related kinetoplastid protozoa, in which TGA codes
for tryptophan. In addition, a complete absence of CGN triplets may imply the lack of the corresponding tRNA species. COI
cDNAs from E. gracilis possess short 5′ and 3′ untranslated transcribed sequences and lack a 3′ polyA] tail.
The COI gene does not require uridine insertion/deletion RNA editing, as occurs in kinetoplastid mitochondria, to be functional,
and no short guide RNA-like molecules could be visualized by labeling total mitochondrial RNA with α-32P]GTP and guanylyl transferase. In spite of the differences in codon usage and the 3′ end structures of mRNAs, phylogenetic
analysis using the COI and hsp60 protein sequences suggests a monophyletic relationship between the mitochondrial genomes
of E. gracilis and of the kinetoplastids, which is consistent with the phylogenetic relationship of these groups previously obtained using
nuclear ribosomal RNA sequences.
Received: 5 March 1996 / Accepted: 31 July 1996 |
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Keywords: | : Mitochondrial gene — Codon usage — Mitochondrial phylogeny — Euglena gracilis— RNA editing |
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