title: Insights into the olfactory system of the ectoparasite Caligus rogercresseyi: molecular characterization and gene transcription analysis of novel ionotropic receptors.
abstract: Although various elements of the olfactory system have been elucidated in insects, it remains practically unstudied in crustaceans at a molecular level. Among crustaceans, some species are classified as ectoparasites that impact the finfish aquaculture industry. Thus, there is an urgent need to identify and comprehend the signaling pathways used by these in host recognition. The present study, through RNA-seq and qPCR analyses, found novel transcripts involved in the olfactory system of Caligus rogercresseyi, in addition to the transcriptomic patterns expressed during different stages of salmon lice development. From a transcriptomic library generated by Illumina sequencing, contigs that annotated for ionotropic receptors and other genes implicated in the olfactory system were identified and extracted. Full length mRNA was obtained for the ionotropic glutamate receptor 25, which had 3923 bp, and for the glutamate receptor ionotropic kainate 2, which had 2737 bp. Furthermore, two other transcripts identified as glutamate receptor, ionotropic kainate 2-like were found. In silico analysis was performed for the transcription expression from different stages of development in C. rogercresseyi, and clusters according to RPKM values were constructed. Gene transcription data were validated through qPCR assays in ionotropic receptors, and showed an expression of glutamate receptor 25 associated with the copepodid stage whereas adults, especially male adults, were associated with the kainate 2 and kainate 2-like transcripts. Additionally, gene transcription analysis of the ionotropic receptors showed an overexpression in response to the presence of masking compounds and immunostimulant in salmon diets. This response correlated to a reduction in sea lice infection following in vivo challenge. Diets with masking compounds showed a decrease of lice infestation of up to 25%. This work contributes to the available knowledge on chemosensory systems in this ectoparasite, providing novel elements towards understanding the host-finding process of the salmon louse C. rogercresseyi.
authors.affiliation: Laboratory of Biotechnology and Aquatic Genomics, Interdisciplinary Center for Aquaculture Research (INCAR), University of Concepción, P.O. Box 160-C, Concepción, Chile.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Núñez-Acuña
authors.affiliation: Laboratory of Biotechnology and Aquatic Genomics, Interdisciplinary Center for Aquaculture Research (INCAR), University of Concepción, P.O. Box 160-C, Concepción, Chile.
authors.forename: Valentina
authors.initials: V
authors.lastname: Valenzuela-Muñoz
authors.affiliation: EWOS Innovation Chile, Camino a Pargua km 57, Colaco km 5, Calbuco, Chile.
authors.forename: Jorge Pino
authors.initials: JP
authors.lastname: Marambio
authors.affiliation: EWOS Innovation Norway, N-4335 Dirdal, Norway.
authors.forename: Simon
authors.initials: S
authors.lastname: Wadsworth
authors.affiliation: Laboratory of Biotechnology and Aquatic Genomics, Interdisciplinary Center for Aquaculture Research (INCAR), University of Concepción, P.O. Box 160-C, Concepción, Chile.
authors.forename: Cristian
authors.initials: C
authors.lastname: Gallardo-Escárate
mesh_terms: D000818:Animals; D001483:Base Sequence; D033342:Copepoda / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D004478:Ectoparasitic Infestations / Q000469:parasitology / Q000662:veterinary*; D005260:Female; D005393:Fish Diseases / Q000469:parasitology*; D005786:Gene Expression Regulation; D008297:Male; D008969:Molecular Sequence Data; D009830:Olfactory Bulb / Q000033:anatomy & histology / Q000502:physiology; D018034:Olfactory Receptor Neurons / Q000033:anatomy & histology / Q000502:physiology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D018092:Kainic Acid Receptors / Q000235:genetics; D012487:Salmonidae / Q000469:parasitology*; D016415:Sequence Alignment; D012903:Smell / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics; D059467:Transcriptome / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D018092:Kainic Acid Receptors
keywords: Caligus rogercresseyi; Ionotropic receptor; Olfactory receptor; RNA-seq