A stilbonematid nematode EST project

In the last years it became clear that the study of biological systems in which invertebrates and procaryotes succeed to beneficially interact with each other could enlarge our understanding of how chronic pathogenic infections develop and persist. Among the very few known non-pathogenic nematode-bacteria associations, the most spectacular ones are those involving the Stilbonematinae (Desmodoridae, Chromadoria). Chemoautotrophic sulfur- oxidizing bacteria arranged in a genus- or even species-specific pattern cover the cuticle of these marine nematodes, irrespectively of their age. The association of stilbonematids of the genus Laxus could be specifically disrupted by incubation in D-mannose and a worm cDNA predicted to encode for a secreted mannose-binding C- type lectin (provisionally called STIL-1) was identified. STIL-1, which shares significant identity with mammalians dendritic cell immunoreceptors, is supposedly only one of a whole battery of proteins encoded by symbiosis- specific genes. Here we propose to carry out a stilbonematid expressed sequence tag (EST) project to identify other molecular key players belonging to this battery. The potential of a stilbonematid EST-based gene discovery approach goes beyond that of identifying adaptations requisite for bacterial association at the molecular level. Indeed, the availability of the full genome sequence of three Caenorhabditis species and of Brugia malayi, as well as EST datasets of many parasitic nematodes, yields an exceptional opportunity to compare free-living, parasitic and symbiotic gene sequences and structures. Finally, from a phylogenetic point of view, the acquisition from stilbonematid sequence data will help rooting the main radiation of the Secernentea and resolving the trichotomy at the base of the Nematoda.

In the last years it became clear that the study of biological systems in which invertebrates and procaryotes succeed to beneficially interact with each other could enlarge our understanding of how chronic pathogenic infections develop and persist. Among the very few known non-pathogenic nematode-bacteria associations, the most spectacular ones are those involving the Stilbonematinae (Desmodoridae, Chromadoria). Chemoautotrophic sulfur- oxidizing bacteria arranged in a genus- or even species-specific pattern cover the cuticle of these marine nematodes, irrespectively of their age. The association of stilbonematids of the genus Laxus could be specifically disrupted by incubation in D-mannose and a worm cDNA predicted to encode for a secreted mannose-binding C- type lectin (provisionally called STIL-1) was identified. STIL-1, which shares significant identity with mammalians dendritic cell immunoreceptors, is supposedly only one of a whole battery of proteins encoded by symbiosis- specific genes. Here we propose to carry out a stilbonematid expressed sequence tag (EST) project to identify other molecular key players belonging to this battery. The potential of a stilbonematid EST-based gene discovery approach goes beyond that of identifying adaptations requisite for bacterial association at the molecular level. Indeed, the availability of the full genome sequence of three Caenorhabditis species and of Brugia malayi, as well as EST datasets of many parasitic nematodes, yields an exceptional opportunity to compare free-living, parasitic and symbiotic gene sequences and structures. Finally, from a phylogenetic point of view, the acquisition from stilbonematid sequence data will help rooting the main radiation of the Secernentea and resolving the trichotomy at the base of the Nematoda.