title: daf-7 and the development of Strongyloides ratti and Parastrongyloides trichosuri.
abstract: daf-7 is a key ligand in one of the three pathways that control dauer larva development in Caenorhabditis elegans. Given the similarities between dauer larvae of free-living nematodes and third stage infective larvae of animal parasitic nematodes, we hypothesised that daf-7 may be involved in the development of these infective larvae. To investigate this, we cloned daf-7 orthologues from Strongyloides ratti and Parastrongyloides trichosuri and analysed their RNA level by semi-quantitative RT-PCR during the S. ratti and P. trichosuri life cycles and in a range of in vitro and in vivo conditions. We found that, in both species, the RNA level of daf-7 was low in free-living stages but peaked in the infective L3 (iL3) stage with little or no expression in the parasitic stages. This contrasts with the daf-7 RNA level in C. elegans, which peaks in L1, decreases thereafter, and is absent in dauer larvae. The RNA level of daf-7 in infective larvae was reduced by larval penetration of host skin or development in the host, but not by a shift to the body temperature of the host.
authors.affiliation: School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
authors.forename: Matt
authors.initials: M
authors.lastname: Crook
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Thompson
authors.forename: Warwick N
authors.initials: WN
authors.lastname: Grant
authors.forename: Mark E
authors.initials: ME
authors.lastname: Viney
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000254:growth & development; D008018:Life Cycle Stages; D008297:Male; D008969:Molecular Sequence Data; D048329:Phalangeridae / Q000469:parasitology; D017168:Rhabditida / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017196:Rhabditida Infections / Q000469:parasitology / Q000662:veterinary; D017422:Sequence Analysis, DNA; D017170:Strongyloides ratti / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D013322:Strongyloidiasis / Q000469:parasitology / Q000662:veterinary; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; C102095:DAF-7 protein, C elegans; D015801:Helminth Proteins; D016212:Transforming Growth Factor beta