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Analysis of two genomes from the mitochondrion-like organelle of the intestinal parasite Blastocystis: complete sequences, gene content, and genome organization.

Pérez-Brocal V, Clark CG - Mol. Biol. Evol. (2008)

Bottom Line: The human parasitic stramenopile Blastocystis is a rare example of an anaerobic eukaryote with organelles that have retained some mitochondrial characteristics, including a genome, whereas they lack others, such as cytochromes.Here we report the sequence and comparative analysis of the organellar genome from two different Blastocystis isolates as well as a comparison to other genomes from stramenopile mitochondria.Analysis of the characteristics displayed by the unique Blastocystis organelle genome gives us an insight into the initial evolutionary steps that may have led from mitochondria to hydrogenosomes and mitosomes.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.

ABSTRACT
Acquisition of mitochondria by the ancestor of all living eukaryotes represented a crucial milestone in the evolution of the eukaryotic cell. Nevertheless, a number of anaerobic unicellular eukaryotes have secondarily discarded certain mitochondrial features, leading to modified organelles such as hydrogenosomes and mitosomes via degenerative evolution. These mitochondrion-derived organelles have lost many of the typical characteristics of aerobic mitochondria, including certain metabolic pathways, morphological traits, and, in most cases, the organellar genome. So far, the evolutionary pathway leading from aerobic mitochondria to anaerobic degenerate organelles has remained unclear due to the lack of examples representing intermediate stages. The human parasitic stramenopile Blastocystis is a rare example of an anaerobic eukaryote with organelles that have retained some mitochondrial characteristics, including a genome, whereas they lack others, such as cytochromes. Here we report the sequence and comparative analysis of the organellar genome from two different Blastocystis isolates as well as a comparison to other genomes from stramenopile mitochondria. Analysis of the characteristics displayed by the unique Blastocystis organelle genome gives us an insight into the initial evolutionary steps that may have led from mitochondria to hydrogenosomes and mitosomes.

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Gene and physical map of the Blastocystis MLO genome. Black blocks represent genes and ORFs that are transcribed clockwise (outside of circle) or counterclockwise (inside of circle). Gray blocks represent tRNA genes. tRNA genes are identified by their linked amino acid (single-letter code). Mf and Me1/Me2 are initiator and elongator methionyl tRNAs, respectively. The inner circle shows the size scale. The map was created using GenomeViz 1.1 [Ghai et al. 2004]). Because of overlapping coding regions (see text and supplementary table S2, Supplementary Material online), gaps between adjacent genes are not always present.
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fig1: Gene and physical map of the Blastocystis MLO genome. Black blocks represent genes and ORFs that are transcribed clockwise (outside of circle) or counterclockwise (inside of circle). Gray blocks represent tRNA genes. tRNA genes are identified by their linked amino acid (single-letter code). Mf and Me1/Me2 are initiator and elongator methionyl tRNAs, respectively. The inner circle shows the size scale. The map was created using GenomeViz 1.1 [Ghai et al. 2004]). Because of overlapping coding regions (see text and supplementary table S2, Supplementary Material online), gaps between adjacent genes are not always present.

Mentions: The MLO genome consists of a circular mapping molecule of 27,719 and 28,382 bp in Blastocystis sp. DMP/02-328 and NandII, respectively. The synteny between the two MLO genomes is complete, with no evidence of rearrangements having occurred since the divergence of subtypes 1 and 4, represented by Blastocystis sp. NandII and DMP/02-328, respectively. The genome consists of 45 genes, of which 27 are ORFs (23 of them with identifiable orthologs) and the rest structural RNA genes (the small and large subunit ribosomal RNAs, plus a set of 16 tRNAs, including two distinct tRNA-Mete genes). The structure of the Blastocystis sp. DMP/02-328 MLO genome is displayed in figure 1. It is a highly compact genome, with coding regions representing 96% of its total length and overlapping genes being a common feature.


Analysis of two genomes from the mitochondrion-like organelle of the intestinal parasite Blastocystis: complete sequences, gene content, and genome organization.

Pérez-Brocal V, Clark CG - Mol. Biol. Evol. (2008)

Gene and physical map of the Blastocystis MLO genome. Black blocks represent genes and ORFs that are transcribed clockwise (outside of circle) or counterclockwise (inside of circle). Gray blocks represent tRNA genes. tRNA genes are identified by their linked amino acid (single-letter code). Mf and Me1/Me2 are initiator and elongator methionyl tRNAs, respectively. The inner circle shows the size scale. The map was created using GenomeViz 1.1 [Ghai et al. 2004]). Because of overlapping coding regions (see text and supplementary table S2, Supplementary Material online), gaps between adjacent genes are not always present.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2568035&req=5

fig1: Gene and physical map of the Blastocystis MLO genome. Black blocks represent genes and ORFs that are transcribed clockwise (outside of circle) or counterclockwise (inside of circle). Gray blocks represent tRNA genes. tRNA genes are identified by their linked amino acid (single-letter code). Mf and Me1/Me2 are initiator and elongator methionyl tRNAs, respectively. The inner circle shows the size scale. The map was created using GenomeViz 1.1 [Ghai et al. 2004]). Because of overlapping coding regions (see text and supplementary table S2, Supplementary Material online), gaps between adjacent genes are not always present.
Mentions: The MLO genome consists of a circular mapping molecule of 27,719 and 28,382 bp in Blastocystis sp. DMP/02-328 and NandII, respectively. The synteny between the two MLO genomes is complete, with no evidence of rearrangements having occurred since the divergence of subtypes 1 and 4, represented by Blastocystis sp. NandII and DMP/02-328, respectively. The genome consists of 45 genes, of which 27 are ORFs (23 of them with identifiable orthologs) and the rest structural RNA genes (the small and large subunit ribosomal RNAs, plus a set of 16 tRNAs, including two distinct tRNA-Mete genes). The structure of the Blastocystis sp. DMP/02-328 MLO genome is displayed in figure 1. It is a highly compact genome, with coding regions representing 96% of its total length and overlapping genes being a common feature.

Bottom Line: The human parasitic stramenopile Blastocystis is a rare example of an anaerobic eukaryote with organelles that have retained some mitochondrial characteristics, including a genome, whereas they lack others, such as cytochromes.Here we report the sequence and comparative analysis of the organellar genome from two different Blastocystis isolates as well as a comparison to other genomes from stramenopile mitochondria.Analysis of the characteristics displayed by the unique Blastocystis organelle genome gives us an insight into the initial evolutionary steps that may have led from mitochondria to hydrogenosomes and mitosomes.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.

ABSTRACT
Acquisition of mitochondria by the ancestor of all living eukaryotes represented a crucial milestone in the evolution of the eukaryotic cell. Nevertheless, a number of anaerobic unicellular eukaryotes have secondarily discarded certain mitochondrial features, leading to modified organelles such as hydrogenosomes and mitosomes via degenerative evolution. These mitochondrion-derived organelles have lost many of the typical characteristics of aerobic mitochondria, including certain metabolic pathways, morphological traits, and, in most cases, the organellar genome. So far, the evolutionary pathway leading from aerobic mitochondria to anaerobic degenerate organelles has remained unclear due to the lack of examples representing intermediate stages. The human parasitic stramenopile Blastocystis is a rare example of an anaerobic eukaryote with organelles that have retained some mitochondrial characteristics, including a genome, whereas they lack others, such as cytochromes. Here we report the sequence and comparative analysis of the organellar genome from two different Blastocystis isolates as well as a comparison to other genomes from stramenopile mitochondria. Analysis of the characteristics displayed by the unique Blastocystis organelle genome gives us an insight into the initial evolutionary steps that may have led from mitochondria to hydrogenosomes and mitosomes.

Show MeSH
Related in: MedlinePlus