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The mitochondrial genome of Toxocara canis.

Jex AR, Waeschenbach A, Littlewood DT, Hu M, Gasser RB - PLoS Negl Trop Dis (2008)

Bottom Line: In addition, the zoonotic potential of related species of Toxocara, such as T. cati and T. malaysiensis, is not well known.In the present study, the mitochondrial genome of T. canis was amplified by long-range polymerase chain reaction (long PCR) and sequenced using a primer-walking strategy.This circular mitochondrial genome was 14162 bp and contained 12 protein-coding, 22 transfer RNA, and 2 ribosomal RNA genes consistent for secementean nematodes, including Ascaris suum and Anisakis simplex (Ascaridida).

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia. ajex@unimelb.edu.au

ABSTRACT
Toxocara canis (Ascaridida: Nematoda), which parasitizes (at the adult stage) the small intestine of canids, can be transmitted to a range of other mammals, including humans, and can cause the disease toxocariasis. Despite its significance as a pathogen, the genetics, epidemiology and biology of this parasite remain poorly understood. In addition, the zoonotic potential of related species of Toxocara, such as T. cati and T. malaysiensis, is not well known. Mitochondrial DNA is known to provide genetic markers for investigations in these areas, but complete mitochondrial genomic data have been lacking for T. canis and its congeners. In the present study, the mitochondrial genome of T. canis was amplified by long-range polymerase chain reaction (long PCR) and sequenced using a primer-walking strategy. This circular mitochondrial genome was 14162 bp and contained 12 protein-coding, 22 transfer RNA, and 2 ribosomal RNA genes consistent for secementean nematodes, including Ascaris suum and Anisakis simplex (Ascaridida). The mitochondrial genome of T. canis provides genetic markers for studies into the systematics, population genetics and epidemiology of this zoonotic parasite and its congeners. Such markers can now be used in prospecting for cryptic species and for exploring host specificity and zoonotic potential, thus underpinning the prevention and control of toxocariasis in humans and other hosts.

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The secondary structure predicted for the small subunit (rrnS) of the rRNA gene in the mitochondrial genome of Toxocara canis.Bonds between C∶G and U∶A are indicated by a straight line and those between U∶G by a closed circle [35]. Conserved secondary structure elements [102] indicated by numbers 1–48.
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pntd-0000273-g004: The secondary structure predicted for the small subunit (rrnS) of the rRNA gene in the mitochondrial genome of Toxocara canis.Bonds between C∶G and U∶A are indicated by a straight line and those between U∶G by a closed circle [35]. Conserved secondary structure elements [102] indicated by numbers 1–48.

Mentions: All but the two serine tRNAs (AGN and UCN) had a predicted secondary structure containing a DHU arm and loop and a TV-replacement loop instead of the TψC arm and loop (Figure 2). As reported previously for secernentean nematodes [15],[16],[43],[44], the two serine tRNAs each contained the TψC arm and loop but lacked the DHU arm and loop. The rrnL and rrnS genes were 923 and 693 bp in length, respectively; the predicted secondary structure of each of these two genes are displayed in Figure 3 (rrnL) and Figure 4 (rrnS). The AT-content of the sequences of rrnL, rrnS and the AT-rich (“control”) region were 77.9%, 66.5% and 78.1%, respectively. The relatively low AT-richness exhibited in the mitochondrial genome of T. canis was pronounced for the rRNA genes: The AT-content of the rrnL sequence was 4.2% and 4.9% less compared with Anisakis simplex (76.1%) [17] and Ascaris suum (76.8%) [18], respectively. The AT-content of the rrnS sequence of T. canis was 5.5% and 5.4% less than that reported for Anisakis simplex (72.0%) [17] and Ascaris suum (71.9%) [18], respectively. Interestingly, the AT-content of the T. canis mitochondrial rRNA genes does not alter their predicted secondary structures with respect to those of other secernentean nematodes studied to date [35],[39],[41],[42].


The mitochondrial genome of Toxocara canis.

Jex AR, Waeschenbach A, Littlewood DT, Hu M, Gasser RB - PLoS Negl Trop Dis (2008)

The secondary structure predicted for the small subunit (rrnS) of the rRNA gene in the mitochondrial genome of Toxocara canis.Bonds between C∶G and U∶A are indicated by a straight line and those between U∶G by a closed circle [35]. Conserved secondary structure elements [102] indicated by numbers 1–48.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2483351&req=5

pntd-0000273-g004: The secondary structure predicted for the small subunit (rrnS) of the rRNA gene in the mitochondrial genome of Toxocara canis.Bonds between C∶G and U∶A are indicated by a straight line and those between U∶G by a closed circle [35]. Conserved secondary structure elements [102] indicated by numbers 1–48.
Mentions: All but the two serine tRNAs (AGN and UCN) had a predicted secondary structure containing a DHU arm and loop and a TV-replacement loop instead of the TψC arm and loop (Figure 2). As reported previously for secernentean nematodes [15],[16],[43],[44], the two serine tRNAs each contained the TψC arm and loop but lacked the DHU arm and loop. The rrnL and rrnS genes were 923 and 693 bp in length, respectively; the predicted secondary structure of each of these two genes are displayed in Figure 3 (rrnL) and Figure 4 (rrnS). The AT-content of the sequences of rrnL, rrnS and the AT-rich (“control”) region were 77.9%, 66.5% and 78.1%, respectively. The relatively low AT-richness exhibited in the mitochondrial genome of T. canis was pronounced for the rRNA genes: The AT-content of the rrnL sequence was 4.2% and 4.9% less compared with Anisakis simplex (76.1%) [17] and Ascaris suum (76.8%) [18], respectively. The AT-content of the rrnS sequence of T. canis was 5.5% and 5.4% less than that reported for Anisakis simplex (72.0%) [17] and Ascaris suum (71.9%) [18], respectively. Interestingly, the AT-content of the T. canis mitochondrial rRNA genes does not alter their predicted secondary structures with respect to those of other secernentean nematodes studied to date [35],[39],[41],[42].

Bottom Line: In addition, the zoonotic potential of related species of Toxocara, such as T. cati and T. malaysiensis, is not well known.In the present study, the mitochondrial genome of T. canis was amplified by long-range polymerase chain reaction (long PCR) and sequenced using a primer-walking strategy.This circular mitochondrial genome was 14162 bp and contained 12 protein-coding, 22 transfer RNA, and 2 ribosomal RNA genes consistent for secementean nematodes, including Ascaris suum and Anisakis simplex (Ascaridida).

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia. ajex@unimelb.edu.au

ABSTRACT
Toxocara canis (Ascaridida: Nematoda), which parasitizes (at the adult stage) the small intestine of canids, can be transmitted to a range of other mammals, including humans, and can cause the disease toxocariasis. Despite its significance as a pathogen, the genetics, epidemiology and biology of this parasite remain poorly understood. In addition, the zoonotic potential of related species of Toxocara, such as T. cati and T. malaysiensis, is not well known. Mitochondrial DNA is known to provide genetic markers for investigations in these areas, but complete mitochondrial genomic data have been lacking for T. canis and its congeners. In the present study, the mitochondrial genome of T. canis was amplified by long-range polymerase chain reaction (long PCR) and sequenced using a primer-walking strategy. This circular mitochondrial genome was 14162 bp and contained 12 protein-coding, 22 transfer RNA, and 2 ribosomal RNA genes consistent for secementean nematodes, including Ascaris suum and Anisakis simplex (Ascaridida). The mitochondrial genome of T. canis provides genetic markers for studies into the systematics, population genetics and epidemiology of this zoonotic parasite and its congeners. Such markers can now be used in prospecting for cryptic species and for exploring host specificity and zoonotic potential, thus underpinning the prevention and control of toxocariasis in humans and other hosts.

Show MeSH
Related in: MedlinePlus