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Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing.

ABSTRACT: BACKGROUND:Infection with the parasitic nematode, Baylisascaris schroederi (Ascaridida: Nematoda), is one of the most important causes of death in giant pandas, and was responsible for half of deaths between 2001 and 2005. Mitochondrial (mt) DNA sequences of parasites can unveil their genetic diversity and depict their likely dynamic evolution and therefore may provide insights into parasite survival and responses to host changes, as well as parasite control. METHODS:Based on previous studies, the present study further annotated the genetic variability and structure of B. schroederi populations by combining two different mtDNA markers, ATPase subunit 6 (atp6) and cytochrome c oxidase subunit I (cox1). Both sequences were completely amplified and genetically analyzed among 57 B. schroederi isolates, which were individually collected from ten geographical regions located in three important giant panda habitats in China (Minshan, Qionglai and Qinling mountain ranges). RESULTS:For the DNA dataset, we identified 20 haplotypes of atp6, 24 haplotypes of cox1, and 39 haplotypes of atp6?+?cox1. Further haplotype network and phylogenetic analyses demonstrated that B. schroederi populations were predominantly driven by three common haplotypes, atp6 A1, cox1 C10, and atp6?+?cox1 H11. However, due to low rates of gene differentiation between the three populations, both the atp6 and cox1 genes appeared not to be significantly associated with geographical divisions. In addition, high gene flow was detected among the B. schroederi populations, consistent with previous studies, suggesting that this parasite may be essentially homogenous across endemic areas. Finally, neutrality tests and mismatch analysis indicated that B. schroederi had undergone earlier demographic expansion. CONCLUSIONS:These results confirmed that B. schroederi populations do not follow a pattern of isolation by distance, further revealing the possible existence of physical connections before geographic separation. This study should also contribute to an improved understanding of the population genetics and evolutionary biology of B. schroederi and assist in the control of baylisascariasis in giant pandas.

SUBMITTER: Xie Y

PROVIDER: S-EPMC4292857 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing.

Xie Yue Y Zhou Xuan X Zhang Zhihe Z Wang Chengdong C Sun Yun Y Liu Tianyu T Gu Xiaobin X Wang Tao T Peng Xuerong X Yang Guangyou G

Parasites & vectors 20141223

<h4>Background</h4>Infection with the parasitic nematode, Baylisascaris schroederi (Ascaridida: Nematoda), is one of the most important causes of death in giant pandas, and was responsible for half of deaths between 2001 and 2005. Mitochondrial (mt) DNA sequences of parasites can unveil their genetic diversity and depict their likely dynamic evolution and therefore may provide insights into parasite survival and responses to host changes, as well as parasite control.<h4>Methods</h4>Based on prev ...[more]

PMID: 25532965

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Project description:Baylisascaris schroederi, an intestinal nematode of the giant panda, is the cause of the often fatal disease, baylisascariasis. Glutathione S-transferases (GSTs) are versatile enzymes that can affect parasite survival and parasite-host interactions and, are therefore, potential targets for the development of diagnostic tests and vaccines.In this study, we identified a full-length cDNA that encoded a novel, secretory sigma-like GST (Bsc-GST?) from a B. schroederi-omic dataset. Following cloning and sequencing, sequence and structural analyses and comparative modeling were performed using online-bioinformatics and proteomics tools. The recombinant Bsc-GST? (rBsc-GST?) protein was prokaryotically expressed and then used to detect antigenicity and reactivity using immunoblotting assays. In addition, the native protein in female adult B. schroederi was located via immunofluorescence techniques, while the preliminary ELISA-based serodiagnostic potential of rBsc-GST? was assessed in native and infected mouse sera.Bsc-GST? contained a 621-bp open reading frame that encoded a polypeptide of 206 amino acids with two typical sigma GST domain profiles, including a GST_N_Sigma_like at the N-terminus and a GST_C_Sigma_like at the C-terminus. The presence of an N-terminal signal sequence indicated that Bsc-GST? was a secretory protein. Sequence alignment and phylogenetic analyses showed that Bsc-GST? was a nematode-specific member of the Sigma class GSTs and shared the closest genetic distance with its homologue in Ascaris suum. Further comparative structure analyses indicated that Bsc-GST? possessed the essential structural motifs (e.g., ???????) and the consensus secondary or tertiary structure that is typical for other characterized GST?s. Immunolocalization revealed strong distributions of native Bsc-GST? in the body hypodermis, lateral chords, gut epithelium, gut microvilli, oviduct epithelium, and ovaries of adult female worms, similar to its homologue in A. suum. Building on good immunogenic properties, rBsc-GST?-based ELISA exhibited a sensitivity of 79.1% and a specificity of 82.0% to detect anti-B. schroederi IgG antibodies in the sera of experimentally infected mice.This study presents a comprehensive demonstration of sequence and structural-based analysis of a new, secretory sigma-like GST from a nematode, and its good serodiagnostic performance suggests that rBsc-GST? has the potential to detect B. schroederi and, therefore, could be used to develop an ELISA-based serological test to diagnose baylisascariasis in giant pandas.

Project description:BackgroundBaylisascaris schroederi is one of the most common nematodes of the giant panda, and can cause severe baylisascarosis in both wild and captive giant pandas. Previous studies of the giant pandas indicated that this population is genetically distinct, implying the presence of a new subspecies. Based on the co-evolution between the parasite and the host, the aim of this study was to investigate the genetic differentiation in the B. schroederi population collected from giant pandas inhabiting different mountain ranges, and further to identify whether the evolution of this parasite correlates with the evolution of giant pandas.MethodsIn this study, 48 B. schroederi were collected from 28 wild giant pandas inhabiting the Qinling, Minshan and Qionglai mountain ranges in China. The complete sequence of the mitochondrial cytochrome b (mtCytb) gene was amplified by PCR, and the corresponding population genetic diversity of the three mountain populations was determined. In addition, we discussed the evolutionary relationship between B. schroederi and its host giant panda.ResultsFor the DNA dataset, insignificant Fst values and a significant, high level of gene flow were detected among the three mountain populations of B. schroederi, and high genetic variation within populations and a low genetic distance were observed. Both phylogenetic analyses and network mapping of the 16 haplotypes revealed a dispersed pattern and an absence of branches strictly corresponding to the three mountain range sampling sites. Neutrality tests and mismatch analysis indicated that B. schroederi experienced a population expansion in the past.ConclusionsTaken together, the dispersed haplotype map, extremely high gene flow among the three populations of B. schroederi, low genetic structure and rapid evolutionary rate suggest that the B. schroederi populations did not follow a pattern of isolation by distance, indicating the existence of physical connections before these populations became geographically separated.

Dataset Information

Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing.

Publications

Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing.

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