The Mitochondrial Genome of Baylisascaris procyonis

Jiabo Deng,Yue Xie,Qiang Wang,Justin David Brown,Deying Yang,Jingchao Lan,Xuerong Peng,Lili Niu,Guangyou Yang,Chengdong Wang,Guiying Hao,Yan Fu,Zhihe Zhang,Shuxian Wang,Huaming Nie,Xiaobin Gu,Ning Yan

doi:10.1371/journal.pone.0027066

Jiabo Deng, Yue Xie + Show 15 more

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https://doi.org/10.1371/journal.pone.0027066

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Abstract

Background Baylisascaris procyonis (Nematoda: Ascaridida), an intestinal nematode of raccoons, is emerging as an important helminthic zoonosis due to serious or fatal larval migrans in animals and humans. Despite its significant veterinary and public health impact, the epidemiology, molecular ecology and population genetics of this parasite remain largely unexplored. Mitochondrial (mt) genomes can provide a foundation for investigations in these areas and assist in the diagnosis and control of B. procyonis. In this study, the first complete mt genome sequence of B. procyonis was determined using a polymerase chain reaction (PCR)-based primer-walking strategy.Methodology/Principal FindingsThe circular mt genome (14781 bp) of B. procyonis contained 12 protein-coding, 22 transfer RNA and 2 ribosomal RNA genes congruent with other chromadorean nematodes. Interestingly, the B. procyonis mtDNA featured an extremely long AT-rich region (1375 bp) and a high number of intergenic spacers (17), making it unique compared with other secernentean nematodes characterized to date. Additionally, the entire genome displayed notable levels of AT skew and GC skew. Based on pairwise comparisons and sliding window analysis of mt genes among the available 11 Ascaridida mtDNAs, new primer pairs were designed to amplify specific short fragments of the genes cytb (548 bp fragment) and rrnL (200 bp fragment) in the B. procyonis mtDNA, and tested as possible alternatives to existing mt molecular beacons for Ascaridida. Finally, phylogenetic analysis of mtDNAs provided novel estimates of the interrelationships of Baylisasaris and Ascaridida.Conclusions/SignificanceThe complete mt genome sequence of B. procyonis sequenced here should contribute to molecular diagnostic methods, epidemiological investigations and ecological studies of B. procyonis and other related ascaridoids. The information will be important in refining the phylogenetic relationships within the order Ascaridida and enriching the resource of markers for systematic, population genetic and evolutionary biological studies of parasitic nematodes of socio-economic importance.

Highlights

Baylisascaris procyonis, a ubiquitous helminth parasite of raccoons (Procyon lotor), is increasingly being recognized as an emerging public health concern in North America, Europe and parts of Asia [1,2]
The B. procyonis mtDNA contained 17 intergenic spacers ranging in length from 1 to 118 bp (211 bp in total) including the non-coding regions (NCRs) region (Table S1), which was the highest number of intergenic spacers identified in a nematode mt genome far [23]
Other faint bands were detected in our polymerase chain reaction (PCR) assays, such as a 300bp band in B. procyonis and multiple bands in B. transfuga, which may relate to the specificity of primer pair A. These results suggested that the limited number of available mt genomes in the genus Baylisascaris is still a major barrier for screening effective mt fragments for PCR specific amplification used for identification and differentiation between B. procyonis and other congeners

Summary

Introduction

Baylisascaris procyonis, a ubiquitous helminth parasite of raccoons (Procyon lotor), is increasingly being recognized as an emerging public health concern in North America, Europe and parts of Asia [1,2]. The nucleotide sequence of the AT-region in the B. procyonis mtDNA appeared to share low similarity (all values ,60%) with that of the ten described Ascaridida species, including the congeneric B. ailuri, B. transfuga and B. schroederi (not shown).

Results

Conclusion