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Snails, worms and flies have different ways to fight viral infection

A study has shown that many invertebrate animals don’t fight viral infection in the same way as ‘model’ animals such as fruit flies. These findings could change the way we think about the evolution of immunity.

Dog whelk
Dog whelks have a different flavour of antiviral RNAi from other invertebrates.

Invertebrate animals (those without backbones such as insects, worms and jellyfish) make up more than 97% of animal species.

Most of what we know about antiviral immunity in these animals has been learned from just a few well-studied laboratory species such as fruit flies and nematode worms - so called ‘model organisms’.

Previous studies have shown that fruit flies, nematode worms, plants and fungi apparently have a similar virus-defence mechanism called ‘RNAi’. 

It was therefore assumed that all invertebrate animals would probably fight virus infection in the same way, but this hadn’t been tested until now.

New flavours of RNAi identified

Now, a new study has found that a range of inveterbrates animals do in fact have different types, or ‘flavours’ of antiviral RNAi, from that foud in fruit flies and nematode worms.

Researchers from the University of Edinburgh sampled starfish, sea anemones, sponges, dog whelks and earthworms from the wild in Scotland.  They found 85 viruses new to science, and were surprised to find that the different animals had different flavours of antiviral RNAi.

While researchers did not find any evidence that starfish, sea anemones, and sponges use antiviral RNAi to defend against RNA virus infection, they found that dog whelks did use RNAi, but that it was different from that in fruit flies.

Unexpectedly, they also found that a common sea weed, the serrated wrack, has RNAi more like that of plants, fungi and fruit flies.

Dr. Fergal Waldron, of the University of Edinburgh’s School of Biological Sciences, who led the study, said: “

This study is a missing piece in the puzzle of how animals have evolved to fight virus infection. These findings point towards a much more complex picture than we previously thought”.

Dr. Darren Obbard, also from the School of Biological Sciences, who supervised the study, said

Until recently it was thought that vertebrates like ourselves had lost antiviral RNAi in our evolutionary past. That is because evidence for vertebrate antiviral RNAi has been very difficult to detect. This may be a feature common to some of our sampled invertebrates, which challenges the traditional dichotomy between vertebrate- and invertebrate-like antiviral immunity.”

The study, published in PLoS Genetics, was supported by the Leverhulme Trust and the Wellcome Trust.

Further information

Catriona Kelly, Press & PR office: 0131 651 4401; 07791 355940; Catriona.Kelly@ed.ac.uk

Related links

University of Edinburgh School of Biological Sciences

Obbard lab website

Stone lab website