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Silencing of the Vasa gene by RNA Interference Affects Embryonic Development and Reproductive Output in the Sea Louse Caligus rogercresseyi

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Abstract

The sea louse Caligus rogercresseyi is a major ectoparasitic copepod that causes significant economic losses in the salmon farming industry. Despite recent advancements, the mechanisms underlying germline and embryo development in this species remain poorly understood. The Vasa gene encodes a highly conserved DEAD box helicase that is required for germ cell formation and function in many species. In this study, the Vasa gene was characterized in C. rogercresseyi, and its expression and function were analyzed. Phylogenetic analysis showed that the Cr-Vasa gene product formed clusters in clades with Vasa proteins from closely related species of crustaceans. Cr-Vasa gene expression patterns were assessed by qPCR, and the results showed a significantly higher relative expression level in adult females compared to copepodid, chalimus, and adult male stages. Tissue-specific localization of Cr-Vasa mRNA in C. rogercresseyi was determined using chromogenic in situ hybridization, and strong positive signal was observed in male testes, but also in the intestine and cuticle, while in females, it was observed in the ovaries, oocytes, cuticle, intestine, and egg strings. RNAi-mediated gene silencing of Cr-Vasa impacted embryonic development and reproductive output in adult female lice. Females from the dsVasa-treated group displayed unusual phenotypes, including shorter egg strings with numerous extra-embryonic inclusions, irregularly shaped abnormal embryos, and aborted egg strings. This study provides insights into the role of the Vasa gene in C. rogercresseyi embryonic development and reproductive output, which may have implications for the control of this parasitic copepod in the salmon farming industry.

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Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We are grateful to Sandra Marin, Melinka Mancilla, and Nitza Vera at Laboratorio de Interacciones Ecológicas, Universidad Austral (Chile), for their sea lice culture assistance and to Sussie Dalvin at the Institute of Marine Research (Norway) for her recommendations regarding the RNAi experiment.

Funding

This study was supported by the ANID-Chile FONDECYT 11150915 and FONDEF ID21I10276 granted to Rodolfo Farlora and ANID-Chile “BECA DE DOCTORADO NACIONAL” No. 21170548 granted to Paulina Bustos. Paulina Bustos and Rodolfo Farlora were also supported by the Centro de Investigación y Gestión de Recursos Naturales (CIGREN) CIDI-UV and the Programa de Apoyo a la Adquisición de Equipamiento Menor from the Universidad de Valparaíso, Chile.

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Authors and Affiliations

  1. Laboratorio de Biotecnología Acuática y Genómica Reproductiva (LABYGER), Instituto de Biología, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, 2360102, Valparaíso, Chile

    Paulina Bustos & Rodolfo Farlora

  2. Doctorado en Acuicultura, Programa Cooperativo Universidad de Chile, Universidad Católica del Norte, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile

    Paulina Bustos

  3. Laboratorio de Genética e Inmunología Molecular, Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile

    Paulina Schmitt

  4. Laboratorio de Biología de la Reproducción y del Desarrollo, Instituto de Biología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile

    Donald I. Brown

  5. Centro de Investigación y Gestión de Recursos Naturales (CIGREN), Universidad de Valparaíso, Valparaíso, Chile

    Rodolfo Farlora

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  1. Paulina Bustos
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  4. Rodolfo Farlora
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Contributions

Paulina Bustos: Conceptualization, methodology, investigation, data curation, formal analysis, writing—original draft, visualization. Paulina Schmitt: Conceptualization, resources, writing—review and editing. Donald Irving Brown: Conceptualization, methodology, resources, writing—review and editing. Rodolfo Farlora: Conceptualization, methodology, resources, writing—review and editing, supervision, project administration, funding acquisition. All authors contributed to the article and approved the submitted version.

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Correspondence to Rodolfo Farlora.

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Bustos, P., Schmitt, P., Brown, D.I. et al. Silencing of the Vasa gene by RNA Interference Affects Embryonic Development and Reproductive Output in the Sea Louse Caligus rogercresseyi. Mar Biotechnol 25, 612–623 (2023). https://doi.org/10.1007/s10126-023-10232-5

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