Complete mitochondrial genomes of Taenia multiceps, T. hydatigena and T. pisiformis: additional molecular markers for a tapeworm genus of human and animal health significance.
BACKGROUND
Mitochondrial genomes provide a rich source of molecular variation of proven and widespread utility in molecular ecology, population genetics and evolutionary biology. The tapeworm genus Taenia includes a diversity of tapeworm parasites of significant human and veterinary importance. Here we add complete sequences of the mt genomes of T. multiceps, T. hydatigena and T. pisiformis, to a data set of 4 published mtDNAs in the same genus. Seven complete mt genomes of Taenia species are used to compare and contrast variation within and between genomes in the genus, to estimate a phylogeny for the genus, and to develop novel molecular markers as part of an extended mitochondrial toolkit.


RESULTS
The complete circular mtDNAs of T. multiceps, T. hydatigena and T. pisiformis were 13,693, 13,492 and 13,387 bp in size respectively, comprising the usual complement of flatworm genes. Start and stop codons of protein coding genes included those found commonly amongst other platyhelminth mt genomes, but the much rarer initiation codon GTT was inferred for the gene atp6 in T. pisiformis. Phylogenetic analysis of mtDNAs offered novel estimates of the interrelationships of Taenia. Sliding window analyses showed nad6, nad5, atp6, nad3 and nad2 are amongst the most variable of genes per unit length, with the highest peaks in nucleotide diversity found in nad5. New primer pairs capable of amplifying fragments of variable DNA in nad1, rrnS and nad5 genes were designed in silico and tested as possible alternatives to existing mitochondrial markers for Taenia.


CONCLUSIONS
With the availability of complete mtDNAs of 7 Taenia species, we have shown that analysis of amino acids provides a robust estimate of phylogeny for the genus that differs markedly from morphological estimates or those using partial genes; with implications for understanding the evolutionary radiation of important Taenia. Full alignment of the nucleotides of Taenia mtDNAs and sliding window analysis suggests numerous alternative gene regions are likely to capture greater nucleotide variation than those currently pursued as molecular markers. New PCR primers developed from a comparative mitogenomic analysis of Taenia species, extend the use of mitochondrial markers for molecular ecology, population genetics and diagnostics.
Jia
Wan-Zhong
WZ
Key Laboratory of Veterinary Parasitology of Gansu Province, Key Laboratory of Zoonoses of Ministry of Agriculture, State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, CAAS, Lanzhou, Gansu Province 730046, The People's Republic of China. jwanzhong@yahoo.com.cn
Yan
Hong-Bin
HB
Guo
Ai-Jiang
AJ
Zhu
Xing-Quan
XQ
Wang
Yu-Chao
YC
Shi
Wan-Gui
WG
Chen
Hao-Tai
HT
Zhan
Fang
F
Zhang
Shao-Hua
SH
Fu
Bao-Quan
BQ
Littlewood
D Timothy J
DT
Cai
Xue-Peng
XP
D000818:Animals; D014644:Genetic Variation; D054629:Genome, Mitochondrial; D006801:Humans; D010802:Phylogeny; D012343:RNA, Transfer / Q000235:genetics; D013621:Taenia / Q000145:classification* / Q000235:genetics*
D012343:RNA, Transfer