The complete mitochondrial genome of the rodent intra-arterial nematodes Angiostrongylus cantonensis and Angiostrongylus costaricensis

Abstract

The two rodent intra-arterial nematodes, Angiostrongylus cantonensis and Angiostrongylus costaricensis, can cause human ill-health. The present study aimed to characterize and compare the mitochondrial (mt) genomes of these two species, and clarify their phylogenetic relationship and the position in the phylum Nematoda. The complete mt genomes of A. cantonensis and A. costaricensis are 13,497 and 13,585 bp in length, respectively. Hence, they are the smallest in the class of Chromadorea characterized thus far. Like many nematode species in the class of Chromadorea, they encode 12 proteins, 22 transfer RNAs, and two ribosomal RNAs. All genes are located on the same strand. Nucleotide identity of the two mt genomes is 81.6%, ranging from 77.7% to 87.1% in individual gene pairs. Our mt genome-wide analysis identified three major gene arrangement patterns (II-1, II-2, and II-3) from 48 nematode mt genomes. Both patterns II-1 and II-2 are distinct from pattern II-3, which covers the Spirurida, supporting a closer relationship between Ascaridida and Strongylida rather than Spirurida. Thymine (T) was highly concentrated on coding strands in Chromadorea, but balanced between the two strands in Enoplea, probably due to the gene arrangement pattern. Interestingly, the gene arrangement pattern of mt genomes and phylogenetic analysis based on concatenated amino acids indicated a closer relationship between the order Ascaridida and Rhabditida rather than Spirurida as indicated in previous studies. These discrepancies call for new research, reassessing the position of the order of Ascaridida in the phylogenetic tree. Once consolidated, the findings are important for population genetic studies and target identification.

Hurdles in the evolutionary epidemiology of Angiostrongylus cantonensis: Pseudogenes, incongruence between taxonomy and DNA sequence variants, and cryptic lineages

“…At the time of our study, we had used two mtDNA genome samples as references in our phylogenetic analyses because they were identified in their respective publications as A. cantonensis . These were NC_013065 (Lv et al., 2012) and KT186242 (Yong, Eamsobhana, Lim, et al., 2015; Yong, Song, et al., 2015), both of which originated from laboratory‐maintained isolates in China or Thailand, respectively. Clade I contained NC_013065 and Clade II had KT186242.…”

“…Recently Song, Yong, and Eamsobhana (2017) compared the whole mtDNA of A. mackerrasae (Aghazadeh, 2015) to KT947978 (Thailand isolate of A. cantonensis , Yong et al., 2016) and to NC_013065 (China isolate of A. cantonensis , Lv et al., 2012). They found across all protein coding genes the following pairwise p ‐distances: A. mackerrasae ‐KT947978 = 1.73%, A. mackerrasae ‐NC_013065 = 3.7%, KT947978‐NC_013065 = 3.52%.…”

“…For example, ribosomal DNA sequences were used to assess metastrongylid nematode relationships (Carreno & Nadler, 2003) or to help survey larvae from mollusk intermediate hosts (Fontanilla & Wade, 2008; Qvarnstrom, Sullivan, Bishop, Hollingsworth, & da Silva, 2007; Qvarnstrom et al., 2010), and ~360‐bp region of the cytochrome c oxidase 1 ( CO 1) gene was used to assess relationships to other species of Angiostrongylus (Eamsobhana et al., 2010). To date, molecular systematic/phylogeographic studies on A. cantonensis have mainly used two mitochondrial (mtDNA) markers, CO 1 and cytochrome b ( CYTB ), where the focus has largely been descriptive in terms of reporting local patterns of haplotype variants (Aghazadeh et al., 2015; Dalton, Fenton, Cleveland, Elsmo, & Yabsley, 2017; Dusitsittipon, Criscione, Morand, Komalamisra, & Thaenkham, 2017; Dusitsittipon, Thaenkham, Watthanakulpanich, Adisakwattana, & Komalamisra, 2015; Eamsobhana, Song, et al., 2017; Eamsobhana, Yong, et al., 2017; Lv et al., 2012; Monte et al., 2012; Moreira et al., 2013; Nakaya et al., 2013; Okano et al., 2014; Rodpai et al., 2016; Simoes et al., 2011; Tokiwa et al., 2012, 2013; Vitta et al., 2016; Yong, Eamsobhana, Song, Prasartvit, & Lim, 2015; Yong, Song, Eamsobhana, Goh, & Lim, 2015; Yong, Song, Eamsobhana, & Lim, 2016). …”

Molecular and pathological studies on Angiostrongylus species in southeast Queensland

“…1), similar in length to those of A. cantonensis (13,497 bp), A. costaricensis (13,585 bp) 133 and A.vasorum (13,422 bp) 132 .…”

“…Each protein coding mt gene was identified by local alignment comparison (performed in all six frames) using amino acid sequences from corresponding genes from mt genomes of A. vasorum, A. cantonensis and A. costaricensis; accession nos.NC_018602, GQ398121 and GQ398122, respectively 132,133 . The large and small subunits (rrnL and rrnS) of mt ribosomal RNA genes were identified by local alignment, and all transfer RNA (tRNA) genes were predicted and annotated based on available data from selected nematode superfamilies, (the Metastrongyloidea, Trichostrongyloidea, Ancylostomatidea and Strongyloidea).…”