Transcriptional differences between hypobiotic and non-hypobiotic preadult larvae of the bovine lungworm Dictyocaulus viviparus

Abstract

The survival of the bovine lungworm Dictyocaulus viviparus, one of the most important parasites in cattle, inside the host is ensured by arrested development during adverse environmental conditions, commonly referred to as hypobiosis. In the present study, a subtractive hybridization approach was used to compare the transcription profiles of hypobiotic and non-hypobiotic larvae (L5hyp and L5, respectively). Thereby, 75 L5hyp-enriched and 58 L5-enriched representative ESTs (rESTs) were identified. Subsequent sequence similarity search revealed that 28 L5hyp-rESTs and 11 L5-rESTs were homologous to known transcripts, whereas 47 L5hyp-rESTs and 47 L5-rESTs showed no homologies with published sequences, thus possibly representing parasitic or even Dictyocaulus-specific genes. The differential transcripts were predicted to be involved in nucleic acid synthesis, DNA binding, metabolic pathways and signal transduction. Overall, data presented in this paper provide a first basis for further characterization and analysis of genes driving normal as well as arrested (hypobiotic) parasite development.

Dictyocaulus viviparus genome, variome and transcriptome elucidate lungworm biology and support future intervention

“…We specifically explored transcription in hypobiotic L5 (L5hyp) in an attempt to infer the molecular mechanism(s) responsible for maintenance of the parasite’s developmental arrest within the host animal, a process critical to the year-to-year survival of D. viviparus in temperate regions. Although L5hyp have undergone the final molt, they are smaller than active L5 and have an underdeveloped genital primordium 16 . Interestingly, the transcriptome profile of L5hyp was more similar to L4 than active L5 ( Fig.…”

“…A total of 217 genes were significantly overexpressed in L5hyp compared with L4 ( Supplementary Table S8 ), and these were enriched for GO terms associated with proteolysis, response to heat, and lipid transport ( Supplementary Table S7 ). A previous study suggested that an upregulation of transcription factors might aid in the initiation and maintenance of the hypobiotic state 16 . We identified 11 TFs among the 417 genes, which are differentially transcribed between L4 and L5hyp, although they are not significantly over-represented.…”

“…D. viviparus were collected from parasite-naïve, experimentally infected Holstein-Friesian calves ( Bos taurus ) as previously described 16 . L1 were isolated from fresh, rectal faeces using the Baermann method.…”

“…Isolated L1 were incubated in tap water for one and six days to develop into L2 and L3, respectively. L3 were chilled to induce hypobiosis and introduced to calves via oral infection; calves were sacrificed and mixed-sex hypobiotic L5 (<5 mm in length) were collected from the lungs 35 days post-infection 16 . Calves infected with un-chilled L3 were sacrificed at seven, 15, and 28 days post-infection for collection of L4, L5, and adults via lung perfusion.…”

“…In the present study, we characterize the draft genome, population variome and developmentally-staged transcriptome of D. viviparus in order to substantially improve our understanding of this pathogen at the molecular level across all defined life cycle stages and its relationship with the bovine host. The Hannover Dv2000 field isolate, a temperate strain from Northern Germany, was selected for this investigation because it has been the subject of previous recombinant vaccine 14 and gene expression studies 15 16 17 , serves as the basis for the lungworm-MSP-ELISA diagnostic assay 18 19 , and (unlike the strain used for producing live vaccine) is capable of undergoing hypobiosis. This is the first comprehensive “omic” study of an economically important nematode parasite of the respiratory system.…”