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Characterization of a novel RXR receptor in the salmon louse (Lepeophtheirus salmonis, Copepoda) regulating growth and female reproduction.

ABSTRACT: Nuclear receptors have crucial roles in all metazoan animals as regulators of gene transcription. A wide range of studies have elucidated molecular and biological significance of nuclear receptors but there are still a large number of animals where the knowledge is very limited. In the present study we have identified an RXR type of nuclear receptor in the salmon louse (Lepeophtheirus salmonis) (i.e. LsRXR). RXR is one of the two partners of the Ecdysteroid receptor in arthropods, the receptor for the main molting hormone 20-hydroxyecdysone (E20) with a wide array of effects in arthropods.Five different LsRXR transcripts were identified by RACE showing large differences in domain structure. The largest isoforms contained complete DNA binding domain (DBD) and ligand binding domain (LBD), whereas some variants had incomplete or no DBD. LsRXR is transcribed in several tissues in the salmon louse including ovary, subcuticular tissue, intestine and glands. By using Q-PCR it is evident that the LsRXR mRNA levels vary throughout the L. salmonis life cycle. We also show that the truncated LsRXR transcript comprise about 50% in all examined samples. We used RNAi to knock-down the transcription in adult reproducing female lice. This resulted in close to zero viable offspring. We also assessed the LsRXR RNAi effects using a L. salmonis microarray and saw significant effects on transcription in the female lice. Transcription of the major yolk proteins was strongly reduced by knock-down of LsRXR. Genes involved in lipid metabolism and transport were also down regulated. Furthermore, different types of growth processes were up regulated and many cuticle proteins were present in this group.The present study demonstrates the significance of LsRXR in adult female L. salmonis and discusses the functional aspects in relation to other arthropods. LsRXR has a unique structure that should be elucidated in the future.

SUBMITTER: Eichner C

PROVIDER: S-EPMC4333900 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Characterization of a novel RXR receptor in the salmon louse (Lepeophtheirus salmonis, Copepoda) regulating growth and female reproduction.

Eichner Christiane C Dalvin Sussie S Skern-Mauritzen Rasmus R Malde Ketil K Kongshaug Heidi H Nilsen Frank F

BMC genomics 20150214

<h4>Background</h4>Nuclear receptors have crucial roles in all metazoan animals as regulators of gene transcription. A wide range of studies have elucidated molecular and biological significance of nuclear receptors but there are still a large number of animals where the knowledge is very limited. In the present study we have identified an RXR type of nuclear receptor in the salmon louse (Lepeophtheirus salmonis) (i.e. LsRXR). RXR is one of the two partners of the Ecdysteroid receptor in arthrop ...[more]

PMID: 25765704

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Project description:BackgroundA microsporidian was previously reported to infect the crustacean parasite, Lepeophtheirus salmonis (Krøyer, 1837) (Copepoda, Caligidae), on farmed Atlantic salmon (Salmo salar L.) in Scotland. The microsporidian was shown to be a novel species with a molecular phylogenetic relationship to Nucleospora (Enterocytozoonidae), but the original report did not assign it to a genus or species. Further studies examined the development of the microsporidian in L. salmonis using electron microscopy and re-evaluated the molecular findings using new sequence data available for the group. Here we report a full description for the microsporidian and assign it to a new genus and species.ResultsThe microsporidian infects subcuticular cells that lie on the innermost region of the epidermal tissue layer beneath the cuticle and along the internal haemocoelic divisions. The mature spores are sub-spherical with a single nucleus and an isofilar polar filament with 5-8 turns in a double coil. The entire development is in direct contact with the host cell cytoplasm and is polysporous. During early merogony, a diplokaryotic nuclear arrangement exists which is absent throughout the rest of the developmental cycle. Large merogonial plasmodia form which divide to form single uninucleate sporonts. Sporogonial plasmodia were not observed; instead, binucleate sporonts divide to form two sporoblasts. Prior to final division, there is a precocious development of the polar filament extrusion apparatus which is associated with large electron lucent inclusions (ELIs). Analyses of DNA sequences reveal that the microsporidian is robustly supported in a clade with other members of the Enterocytozoonidae and confirms a close phylogenetic relationship with Nucleospora.ConclusionThe ultrastructural findings of the precocious development of the polar filament and the presence of ELIs are consistent with those of the Enterocytozoonidae. However, the confirmed presence of an early diplokaryotic stage and a merogonial plasmodium that divides to yield uninucleate sporonts instead of transforming into a sporogonial syncitium, are features not currently associated with the family. Yet, analyses of DNA sequence data clearly place the microsporidian within the Enterocytozoonidae. Therefore, due to the novelty of the copepod host, the ultrastructural findings and the robust nature of the phylogenetic analyses, a new genus should be created within the Enterocytozoonide; Desmozoon lepeophtherii n. gen. n. sp. is proposed.

Dataset Information

Characterization of a novel RXR receptor in the salmon louse (Lepeophtheirus salmonis, Copepoda) regulating growth and female reproduction.

Publications

Characterization of a novel RXR receptor in the salmon louse (Lepeophtheirus salmonis, Copepoda) regulating growth and female reproduction.

Similar Datasets

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