Lice attach to the Atlantic salmon skin and feed on blood and mucus. If untreated, the parasites can create sores that stress and can ultimately lead to death of the fish. Photo: Helge Skodvin © Nofima.

CrispResist

Harnessing cross-species variation in sea lice resistance

 Breeding and genetics    Fish health    Food and health    Nutrition and feed technology  

Do Pacific salmon species carry a secret they could share with Atlantic salmon? What is it in the genes that make these relatives of Atlantic salmon less susceptible to lice? Researchers will now find the answers to these questions, using the gene editing method CRISPR-Cas9.

Time:1. January 2021 – 31. December 2024
Financed by: Norwegian Seafood Research Fund (FHF)
In cooperation with:The Roslin Institute (University of Edinburgh, UK), the Institute of Aquaculture (University of Stirling, UK), Rothamsted Research (UK), the University of Melbourne (Australia), University of Prince Edward Island and Centre for Aquaculture Tehnologies Canada (Canada), Bigelow Laboratory for Ocean Sciences (USA), University of Gothenburg (Sweden), and the Institute of Marine Research (Norway). Benchmark Genetics, Salmar and Mowi are industry partners.
Contact person
Portrettbilde av Nicholas Andrew Robinson
Nicholas Andrew Robinson

Senior Scientist
Phone: +61 448 984 002
nicholas.robinson@nofima.no

More about the project at the financier's website:

Harnessing cross-species variation in sea lice resistance

This project draws together a leading team of researchers from Norway, UK, USA, Canada, Sweden and Australia to discover the mechanisms underlying cross-species variation in host resistance to sea lice, and apply this knowledge to boost Atlantic salmon resistance.

Background

It is well established that certain Pacific salmon species are resistant to sea lice and are able to kill lice in the early stages of parasitisation, whereas Atlantic salmon are highly susceptible.

This difference is primarily due to variation in the effectiveness of the early-stage immune response, but immunomodulation by the lice is likely to play a key role. Improving the innate genetic resistance of the Atlantic salmon host to the lice is a highly promising but underexploited approach to sea lice control.

See animation film about the project:

Objective

The main objective is to elaborate and document the potential for utilising genetic traits and mechanisms of salmon lice resistance in Pacific salmon as tools to achieve an Atlantic salmon with high or full salmon lice (L. salmonis) resistance.

Subobjectives are to:

  • Identify and document genes and mechanisms responsible for the difference in salmon lice resistance between salmonid species.
  • Elaborate and document the potential for utilising the identified genetic traits and mechanisms of salmon lice resistance as tools to achieve an Atlantic salmon with high or full salmon lice resistance.
  • Conduct a risk evaluation on the possibilities for, and consequences of salmon lice adapting to Atlantic salmon with salmon lice resistance.

What we will do

This project will focus on two main potential mechanisms underlying inter-species variation affecting louse parasitisation.

  • Firstly, we will compare the host-parasite interaction in the early stages of louse attachment in detail using transcriptomic and proteomic profiling of tissue sampled from attachment sites.
  • Secondly, we will evaluate differential attractiveness to host-specific semiochemicals across species using louse behavioural analysis.

Integrating results across these two research arms will enable shortlisting of high priority candidate genes for perturbation using genome editing of salmon embryos. Sea lice challenge testing will assess resistance to lice in the edited fish in comparison to unedited family-matched controls. Together with our major industry partners, protocols for breeding and disseminating edited fish as part of ongoing breeding programmes will be designed to limit inbreeding, enable concurrent improvement of other important traits, and minimise the risk of lice evolving to overcome the host resistance.

Outcomes will include fundamental knowledge of mechanisms affecting genetic resistance to sea lice, leading to infection outcomes in Atlantic salmon more closely resembling the resistant Pacific species, together with pathways to implementation to transform the Norwegian salmon farming sector.

This project builds on previous individual and collaborative research projects led by the project leaders at all the institutions in the fields of functional genomics, host-parasite interaction, breeding, preventative lice infestation strategies, risk analysis, semiochemical detection and testing and genome editing.

Follows ethical guidelines

It is up to the aquaculture industry and the authorities, in consultation with other stakeholders, to determine whether these new tools can be deployed. The project will fully explore the potential for using gene editing to prevent lice infestation for salmon farming.

The researchers will follow so-called RRI guidelines (responsible research and innovation).

“We will invite NGOs and others who are interested in seafood production to get input on what social and moral consequences the research and possible implementation could have for Norwegian society. With such input, we can adjust the work underway and create a responsible plan that balances animal welfare, ethics and law”, says project leader Nick Robinson.

Sea lice on salmon. Illustration: Oddvar Dahl © Nofima.

The work

Work package 1: Mechanisms of resistance to sea lice

Elucidation of host-parasite interactions before and after contact with L. salmonis will be evaluated using diverse approaches, harnessing the interdisciplinary background of our project team. Transcriptomics, proteomics and semiochemical profiles of two resistant (coho and pink) and two susceptible (Atlantic and chum) salmon species will be compared, assessing all the different components of resistance: host immune responses, host attractiveness and lice immunomodulation. We have chosen these four species so that we can determine if the same factors affect resistance in all species. We chose chum because they are highly susceptible to lice and, unlike Atlantic salmon, chum, coho and pink are relatively undomesticated, often reared together and phylogenetically close.

The goal is to gain a detailed functional understanding of resistance and susceptibility, pointing to molecular processes and gene networks that can be modified by genome editing to transfer Pacific salmon resistance to Atlantic salmon.

Subobjective: Identify and document genes and mechanisms responsible for the difference in salmon lice resistance between species.

Work package 2: Potential to introduce sea lice resistance loci into Atlantic salmon stocks using genome editing

Genome editing of candidate genes selected based on the results of WP1 will be used to test the effectiveness of transferring sea lice resistance from Pacific species to Atlantic salmon. This WP will also explore how breeding technologies can be most effectively used to disseminate putative resistance loci.

Subobjective: Elaborate and document the potential for utilising the identified genetic traits and mechanisms of salmon lice resistance as tools to achieve an Atlantic salmon with high or full salmon lice resistance.

Work package 3: Risk analysis and modelling of the potential for sea lice to evolve to overcome genetic resistance

This WP integrates a risk analysis on the potential of sea lice to evolve to adapt to resistant salmon. A key plank of our implementation plan will be to minimise the risk of adaptation by lice. We can assume from what data is already available that without mitigation strategies any new adaptations in sea lice could rapidly increase in frequency along the Norwegian coast, rendering resistant salmon ineffective.

Subobjective: Conduct a risk evaluation on the possibilities for, and consequences of salmon lice adapting to Atlantic salmon with salmon lice resistance.

In this project we aim to insert CRISPR-Cas9 to edit targeted genes in Atlantic salmon eggs, which will be grown and tested for their ability to resist salmon lice. Photo: Joe Urrutia © Nofima.

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