Using cDNA libraries and in situ hybridization for analysis of receptors involved in the settlement and metamorphosis of a dominant biofouling tubeworm, Hydroides elegans

Abstract

Larval detection of specific molecular cues on the substratum during settlement and metamorphosis is still a process we know very little about. In order to examine and identify larval receptor systems involved in settlement and metamorphosis, we developed cDNA libraries and performed in situ hybridization (ISH) with different larval stages of the tubeworm Hydroides elegans. This polychaete is a significant problem fouler in warm water ports around the world and is an excellent candidate for investigating molecular reception during larval settlement and metamorphosis. Our first goal was to develop cDNA libraries from pre-competent and metamorphically competent larvae of H. elegans that can be examined for specific receptor genes. Our second goal was to identify candidates for receptors for ligand detection. To this end, we performed ISH with probes developed from these genes to determine where expression occurs in larvae of different developmental stages. One candidate identified using RACE libraries was G_(αq), a guanine nucleotide-binding protein that is a component of transduction pathways of G-protein coupled receptors (GCPRs). We expected this transcript to be present in the apical sensory organ of metamorphically competent larvae if it was involved in ligand detection. ISH did not show expression of this gene in the apical sensory organ in either competent or pre-competent larvae, indicating that perhaps GCPRs are not involved in ligand detection in these larvae. Other likely candidates for receptors during settlement that can be screened using these methods include lectin receptors and ligand-gated ion channels.

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