Background: The Smad proteins function in TGF-β signalling transduction. In the model nematodeCaenorhabditis elegans, the co-Smad, DAF-3 mediates R-Smads and performs a central role in DAF-7 signal transduction, regulating dauer formation and reproductive processes. Considering the divergent evolutionary patterns of the DAF-7 signalling pathway in parasitic nematodes, it is meaningful to explore the structure and function of DAF-3 in parasitic nematodes, such asHaemonchus contortus.Methods: Adaf-3gene (Hc-daf-3) and its predicted product (Hc-DAF-3) were identified fromH. contortusand characterised using integrated genomic and genetic approaches. In addition to immunohistochemistry employed to localiseHc-DAF-3 within adult worm sections, real-time PCR was conducted to assess the transcriptional profiles in different developmental stages ofH. contortusand RNA interference (RNAi) was performedin vitroto assess the functional importance ofHc-daf-3in the development ofH. contortus.Results: Hc-DAF-3 sequences predicted fromHc-daf-3displayed typical features of the co-Smad subfamily. The nativeHc-DAF-3 was localised to the gonad and cuticle of adult parasites. In addition,Hc-daf-3was transcribed in all developmental stages studied, with a higher level in the third-stage larvae (L3) and adult females. Moreover, silencingHc-daf-3by RNAi retarded L4 development.Conclusion: The findings of the present study demonstrated an important role ofHc-DAF-3 in the development ofH. contortuslarvae.

The complete mitochondrial (mt) genome of Trichuris skrjabini has been determined in the current study and subsequently compared with closely related species by phylogenetic analysis based on concatenated datasets of mt amino acid sequences. The whole mt genome of T. skrjabini is circular and 14,011 bp in length. It consists of a total of 37 genes including 13 protein coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNAs) genes, and two non-coding regions. The gene arrangement and contents were consistent with other members of the Trichuridae family including Trichuris suis, Trichuris trichiura, Trichuris ovis, and Trichuris discolor. Phylogenetic analysis based on concatenated datasets of amino acids of the 12 PCGs predicted the distinctiveness of Trichuris skrjabini as compared to other members of the Trichuridae family. Overall, our study supports the hypothesis that T. skrjabini is a distinct species. The provision of molecular data of whole mt genome of T. skrjabini delivers novel genetic markers for future studies of diagnostics, systematics, population genetics, and molecular epidemiology of T. skrjabini.

The complete mitochondrial (mt) genome of Ostertagia trifurcata, a parasitic nematode of small ruminants, has been sequenced and its phylogenetic relationship with selected members from the superfamily Trichostrongyloidea was investigated on the basis of deduced datasets of mt amino acid sequences. The entire mt genome of Ostertagia trifurcata is circular and 14,151 bp in length. It consists of a total of 36 genes comprising 12 genes coding for proteins (PCGs), 2 genes for ribosomal RNA (rRNA), 22 transfer RNA (tRNA) genes and 2 non-coding regions, since all genes are transcribed in the same direction. The phylogenetic analysis based on the concatenated datasets of predicted amino acid sequences of the 12 protein coding genes supported monophylies of the Haemonchidae, Dictyocaulidae and Molineidae families, but rejected monophylies of the Trichostrongylidae family. The complete characterization and provision of the mtDNA sequence of Ostertagia trifurcata provides novel genetic markers for molecular epidemiological investigations, systematics, diagnostics and population genetics of Ostertagia trifurcata and its correspondents.