The Complete Mitochondrial DNA Sequence of <i>Scenedesmus obliquus </i>Reflects an Intermediate Stage in the Evolution of the Green Algal Mitochondrial Genome

Nedelcu, Aurora M.; Lee, William R.; Lemieux, Claude; Gray, Michael W.; Burger, Gertraud

doi:10.1101/gr.10.6.819

Cited by 100 publications

(81 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We are confident in the fact that deeper analysis may provide more precision with regard to the relationship between the genera Helicosporidium and Prototheca. Notably, comparative analysis of mitochondrial genomes has been shown to be a very powerful tool for classification of green algae (Nedelcu et al, 2000). Similarly, observations on ultrastructure and cell biology may provide additional data to confirm our conclusions (Taylor, 1999).…”

Section: Discussionsupporting

confidence: 68%

Phylogenetic analysis identifies the invertebrate pathogen Helicosporidium sp. as a green alga (Chlorophyta).

Tartar

Boucias²,

Adams³

et al. 2002

International Journal of Systematic and Evolutionary Microbiology

View full text Add to dashboard Cite

Historically, the invertebrate pathogens of the genus Helicosporidium were considered to be either protozoa or fungi, but the taxonomic position of this group has not been considered since 1931. Recently, a Helicosporidium sp., isolated from the blackfly Simulium jonesi Stone & Snoddy (Diptera : Simuliidae), has been amplified in the heterologous host Helicoverpa zea. Genomic DNA has been extracted from gradient-purified cysts. The 18S, 28S and 5.8S regions of the Helicosporidium rDNA, as well as partial sequences of the actin and β-tubulin genes, were amplified by PCR and sequenced.Comparative analysis of these nucleotide sequences was performed using neighbour-joining and maximum-parsimony methods. All inferred phylogenetic trees placed Helicosporidium sp. among the green algae (Chlorophyta), and this association was supported by bootstrap and parsimony jackknife values. Phylogenetic analysis focused on the green algae depicted Helicosporidium sp. as a close relative of Prototheca wickerhamii and Prototheca zopfii (Chlorophyta, Trebouxiophyceae), two achlorophylous, pathogenic green algae. On the basis of this phylogenetic analysis, Helicosporidium sp. is clearly neither a protist nor a fungus, but appears to be the first described algal invertebrate pathogen. These conclusions lead us to propose the transfer of the genus Helicosporidium to Chlorophyta, Trebouxiophyceae.

show abstract

Section: Discussionsupporting

confidence: 68%

Phylogenetic analysis identifies the invertebrate pathogen Helicosporidium sp. as a green alga (Chlorophyta).

Tartar

Boucias²,

Adams³

et al. 2002

International Journal of Systematic and Evolutionary Microbiology

View full text Add to dashboard Cite

show abstract

“…The gene content and fragmentation pattern of the ribosomal RNA genes on the mtDNA of S. obliquus suggest that this mitochondrial genome represents an intermediate stage between the Prototheca-like green algae and the Chlamydomonas-like green algae (45). S. obliquus may represent a stage of green algal evolution in which the cox2b gene (encoding for a highly hydrophilic polypeptide) has been transferred to the nucleus, whereas the cox2a gene (encoding a more hydrophobic polypeptide) is retained in the mitochondrial genome.…”

Section: Cox II Is Encoded By Two Distinct Nuclear Genes In Thementioning

confidence: 99%

“…It is possible that in some organisms the transfer of cox2a and cox2b to the nucleus is ongoing, as in some legumes, or has been arrested at an intermediate stage. cox1, cox2, and cox3 were present in the mtDNA of the Chlorophycean alga Scenedesmus obliquus (45,46). However, the cox2 gene was truncated and was predicted to be a pseudogene.…”

Section: Cox II Is Encoded By Two Distinct Nuclear Genes In Thementioning

confidence: 99%

“…S. obliquus may represent a stage of green algal evolution in which the cox2b gene (encoding for a highly hydrophilic polypeptide) has been transferred to the nucleus, whereas the cox2a gene (encoding a more hydrophobic polypeptide) is retained in the mitochondrial genome. Since the mitochondrial genetic code of S. obliquus has diverged from the standard genetic code (45,46), it is likely that the cox2a gene has been retained on the mtDNA since it could not be functionally transferred to the nucleus in its current form. We hypothesize that two independent cox2a and cox2b genes existed in the mitochondrial genome of the common ancestor of Chlamydomonad algae and that these genes were transferred from the mitochondria to the nucleus before the separation of the colorless genera of Polytomella from the main photosynthetic lineage of Chlamydomonas.…”

Section: Cox II Is Encoded By Two Distinct Nuclear Genes In Thementioning

confidence: 99%

See 1 more Smart Citation

Subunit II of Cytochrome c Oxidase in Chlamydomonad Algae Is a Heterodimer Encoded by Two Independent Nuclear Genes

Pérez-Martı́nez

Antaramián

Vázquez-Acevedo

et al. 2001

Journal of Biological Chemistry

View full text Add to dashboard Cite

The mitochondrial genomes of Chlamydomonad algae lack the cox2 gene that encodes the essential subunit COX II of cytochrome c oxidase. COX II is normally a single polypeptide encoded by a single mitochondrial gene. In this work we cloned two nuclear genes encoding COX II from both Chlamydomonas reinhardtii and Polytomella sp. The cox2a gene encodes a protein, COX IIA, corresponding to the N-terminal portion of subunit II of cytochrome c oxidase, and the cox2b gene encodes COX IIB, corresponding to the C-terminal region. The cox2a and cox2b genes are located in the nucleus and are independently transcribed into mRNAs that are translated into separate polypeptides. These two proteins assemble with other cytochrome c oxidase subunits in the inner mitochondrial membrane to form the mature multi-subunit complex. We propose that during the evolution of the Chlorophyte algae, the cox2 gene was divided into two mitochondrial genes that were subsequently transferred to the nucleus. This event was evolutionarily distinct from the transfer of an intact cox2 gene to the nucleus in some members the Leguminosae plant family.

show abstract

“…8). The unicellular green alga Scenedesmus obliquus has retained a three-stop codon system, but only two of the standard stop codons are used, UGA/UAA, with UCA converted to a novel stop codon and UAG recoded as a leucine (9). In contrast, analysis of ORFs in mitochondrial DNA from the vast majority of organisms indicates a reduction from the standard three to two stop codons, retaining UAA/UAG but disposing of UGA, which is decoded by a tRNA Trp (TriTrypDB Database and Refs.…”

Section: Mitochondrially Encoded Translation Termination Codons Vary mentioning

confidence: 99%

Termination of Protein Synthesis in Mammalian Mitochondria

Chrzanowska-Lightowlers

Pajak

Lightowlers

2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

All mechanisms of protein synthesis can be considered in four stages: initiation, elongation, termination, and ribosome recycling. Remarkable progress has been made in understanding how these processes are mediated in the cytosol of many species; however, details of organellar protein synthesis remain sketchy. This is an important omission, as defects in human mitochondrial translation are known to cause disease and may contribute to the aging process itself. In this minireview, we focus on the recent advances that have been made in understanding how one of these processes, translation termination, occurs in the human mitochondrion.The synthesis of proteins is a fundamental mechanism of life. It is clearly essential that the process of mRNA translation, from which proteins are generated, is accurate and well controlled. Translation consists of four stages. The first is initiation, in which a repertoire of initiation factors coordinates the association of mRNA with the ribosomal subunits, recognition of the start codon, and its alignment with an fMet-tRNA Met in the ribosomal P-site. The second stage is elongation, which is facilitated by the action of elongation factors. These act in concert, causing the mRNA to move through the ribosome in steps corresponding to three nucleotides commonly referred to as a codon (1). This stepwise progression allows each codon to be decoded by the cognate aminoacylated tRNA, with the consequent addition of the corresponding amino acid to the nascent polypeptide (2). The third stage is termination, which occurs when a stop codon arrives in the ribosomal A-site and is recognized by a trans-acting protein termed a translation release (RF) 2 or termination factor. This acts in a ribosome-dependent manner, resulting in the nascent polypeptide being separated from the P-site tRNA, allowing the newly synthesized protein to be released from the ribosome. The final stage is that of ribosome recycling, in which the large (LSU) and small (SSU) ribosomal subunits are separated, and the mRNA is released so that the components can be used in a fresh cycle of translation.Extensive research on these individual steps has shown that, across the three domains of life, there are differences in both the cis-and trans-acting factors involved in carrying out these processes, resulting in mechanistic variations. Moreover, investigations into intraorganellar protein synthesis suggest that there are further subtleties to this process, with differences even between organelles from different organisms. To illustrate how the systems can differ as well as retain similarities, this minireview will concentrate on a single step in this process, namely translation termination, and focus on how mitochondria have organized their machinery to accomplish this process. TerminationTermination of translation occurs when a stop codon becomes positioned in the ribosomal A-site and is decoded by a protein moiety. This trans-acting factor (an RF) acts in an analogous fashion to the tRNAs, as it shows sequence-specific reco...

show abstract

The Complete Mitochondrial DNA Sequence of Scenedesmus obliquus Reflects an Intermediate Stage in the Evolution of the Green Algal Mitochondrial Genome

Cited by 100 publications

References 54 publications

Phylogenetic analysis identifies the invertebrate pathogen Helicosporidium sp. as a green alga (Chlorophyta).

Phylogenetic analysis identifies the invertebrate pathogen Helicosporidium sp. as a green alga (Chlorophyta).

Subunit II of Cytochrome c Oxidase in Chlamydomonad Algae Is a Heterodimer Encoded by Two Independent Nuclear Genes

Termination of Protein Synthesis in Mammalian Mitochondria

Contact Info

Product

Resources

About