Molecular identification of candidate chemoreceptor genes and signal transduction components in the sensory epithelium ofAplysia

Abstract

SUMMARYAn ability to sense and respond to environmental cues is essential to the survival of most marine animals. How water-borne chemical cues are detected at the molecular level and processed by molluscs is currently unknown. In this study, we cloned two genes from the marine mollusk Aplysia dactylomela which encode multi-transmembrane proteins. We have performed in situ hybridization that reveals expression and spatial distribution within the long-distance chemosensory organs, the rhinophores. This finding suggests that they could be receptors involved in binding water-borne chemicals and coupling to an intracellular signal pathway. In support of this, we found expression of a phospholipase C and an inositol trisphosphate receptor in the rhinophore sensory epithelia and possibly distributed within outer dendrites of olfactory sensory neurons. In Aplysia, mate attraction and subsequent reproduction is initiated by responding to a cocktail of water-borne protein pheromones released by animal conspecifics. We show that the rhinophore contraction in response to pheromone stimulants is significantly altered following phospholipase C inhibition. Overall, these data provide insight into the molecular components of chemosensory detection in a mollusk. An important next step will be the elucidation of how these coordinate the detection of chemical cues present in the marine environment and activation of sensory neurons.

Ancient Protostome Origin of Chemosensory Ionotropic Glutamate Receptors and the Evolution of Insect Taste and Olfaction

“…In situ hybridisation on 12 µm rhinophore cryosections was performed essentially as described [90]. Sections were photographed using an Olympus BX60 with Nomarski optics and a Nikon Digital Sight DS-U1 camera.…”

Chemoreceptor proteins in the Caribbean spiny lobster, Panulirus argus: Expression of Ionotropic Receptors, Gustatory Receptors, and TRP channels in two chemosensory organs and brain

“…The chemoreceptor proteins used by Protostomia and Deuterostomia are largely different from each other [ 9 ]. Protostomes predominately use ionotropic receptors as chemoreceptors, though GPCRs have been shown to function in a few protostomes, most notably in the nematode Caenorhabditis elegans [ 18 – 20 ], the sea hare Aplysia californica [ 21 , 22 ], and the crown-of-thorns starfish [ 23 ]. In this study, we investigate the major classes of chemoreceptor proteins in the Protostomia, including Ionotropic Receptors (IRs), gustatory receptors (GRs), and transient receptor potential (TRP) channels.…”

Identification of putative olfactory G-protein coupled receptors in Crown-of-Thorns starfish, Acanthaster planci

“…Since their discovery, chemosensory GPCRs have been found across the animal and plant kingdoms, from invertebrates such as the nematode worm Caenorhabditis elegans (which has a larger GPCR repertoire, as a per cent of its genome, than any other animal investigated) [19], to vertebrates including humans [20]. New insights into the molecular basis of olfaction in aquatic invertebrates have been recently reported [21, 22] This has primarily been due to advances in genomics [23]; for example, sequencing of the purple sea urchin Strongylocentrotus purpuratus genome [24] enabled the in silico identification of over 900 rhodopsin-like GPCRs, including a novel family of independently-expanded olfactory receptors, the surreal -GPCRs (Sea URchin Rapidly ExpAnded Lineages of GPCRs) [21]. This research was the first to reveal the molecular components of olfaction in the echinoderm phyla.…”