Dauer signalling pathway model for Haemonchus contortus

Abstract

Background Signalling pathways have been extensively investigated in the free-living nematode Caenorhabditis elegans , but very little is known about these pathways in parasitic nematodes. Here, we constructed a model for the dauer-associated signalling pathways in an economically highly significant parasitic worm, Haemonchus contortus . Methods Guided by data and information available for C. elegans , we used extensive genomic and transcriptomic datasets to infer gene homologues in the dauer-associated pathways, explore developmental transcriptomic, proteomic and phosphoproteomic profiles in H. contortus and study selected molecular structures. Results The canonical cyclic guanosine monophosphate (cGMP), transforming growth factor-β (TGF-β), insulin-like growth factor 1 (IGF-1) and steroid hormone signalling pathways of H. contortus were inferred to represent a total of 61 gene homologues. Compared with C. elegans , H. contortus has a reduced set of genes encoding insulin-like peptides, implying evolutionary and biological divergences between the parasitic and free-living nematodes. Similar transcription profiles were found for all gene homologues between the infective stage of H. contortus and dauer stage of C. elegans . High transcriptional levels for genes encoding G protein-coupled receptors (GPCRs), TGF-β, insulin-like ligands (e.g. ins-1 , ins-17 and ins-18 ) and transcriptional factors (e.g. daf-16 ) in the infective L3 stage of H. contortus were suggestive of critical functional roles in this stage. Conspicuous protein expression patterns and extensive phosphorylation of some components of these pathways suggested marked post-translational modifications also in the L3 stage. The high structural similarity in the DAF-12 ligand binding domain among nematodes indicated functional conservation in steroid (i.e. dafachronic acid) signalling linked to worm development. Conclusions Taken together, this pathway model provides a basis to explore hypotheses regarding biological processes and regulatory mechanisms ( via particular microRNAs, phosphorylation events and/or lipids) associated with the development of H. contortus and related nematodes as well as parasite-host cross talk, which could aid the discovery of new therapeutic targets. Electronic supplementary material The online version of this article (10.1186/s13071-019-3419-6) contains supplementary material, which is available to authorized users.

Dafachronic acid and temperature regulate canonical dauer pathways during Nippostrongylus brasiliensis infectious larvae activation

“…Based on our structural comparisons, we identified three ILP antagonists: Nbr-ILP-1, Nbr-ILP-6, and Nbr-ILP-7. Both Nbr-ilp-1 and Nbr-ilp-6 were downregulated during iL3 activation, similar to downregulation of putative ILP antagonists in H. contortus [46,49] and S. stercoralis [39,44] during iL3 activation. Our transcriptomic data also suggest that Nbr-ilp-2, Nbr-ilp-3, and Nbr-ilp-5 may act as agonists during iL3 activation.…”

“…Furthermore, we are unaware of a study directly examining changes in cGMP levels during iL3 activation in a parasitic nematode and whether this correlates with changes in transcript abundance in signaling pathway components. Thus, we are unable to fully ascertain the biological relevance of the decreases in transcript abundance of daf-11, tax-2, and tax-4 during iL3 activation in N. brasiliensis, although similar decreases have been observed in iL3 activation in H. contortus [49] and to a lesser extent in S. stercoralis [39] and T. canis [63]. Although specific homologs were not identified, receptor-gated ion channels are downregulated in A. ceylanicum during early infection of the golden hamster host [64].…”

“…Most dauer signaling pathway genes found in C. elegans (clade 9A) were also present in N. brasiliensis (clade 9B) [2], with the exception of the number of ILPs, with 40 present in C. elegans [17] and eight identified in N. brasiliensis in this study. A paucity of ILPs in the ruminant parasitic nematode H. contortus (clade 9B) [49], as well as in the more distantly related human parasitic nematode S. stercoralis (clade 10B) [39], suggests that the number of ILPs have expanded in the Caenorhabditis lineage and are found in more modest numbers in parasitic nematodes. Conservation of the components in the other dauer signaling pathways is congruous with both N. brasiliensis and C. elegans having descended from a common ancestor in the clade V/clade 9 lineage [2,50].…”

“…In order to identify canonical dauer signaling pathway components in N. brasiliensis, we performed reciprocal BLAST searches of the N. brasiliensis genome using C. elegans or H. contortus protein sequences as queries, because both species are clade V/clade 9 nematodes and dauer pathway homologs have been identified in H. contortus [49,50]. Since the N. brasiliensis genome assembly is highly fragmented, resulting in some genes being split amongst two or more contigs/scaffolds, we also utilized de novo assembled transcripts to manually reconstruct coding sequences of each gene.…”

Identification and characterization of an R-Smad homologue (Hco-DAF-8) from Haemonchus contortus

“…The Cel-daf-8 gene sequence was obtained from Worm-Base (WS271; code R05D11.1), and an homologue of this gene was identified by searching the C. elegans protein sequence against the non-redundant (nr) protein sequence database using the protein BLAST from the National Center for Biotechnology Information (NCBI) (http://www.ncbi.nlm.nih.gov/BLAST ). Homologues of the Cel-DAF-8 protein were inferred from the H. contortus genomes (PRJEB506 and PRJNA205202) using BLAST/BLAT (https ://wormb ase.org/tools /blast _blat) [23].…”