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News Release - New research highlights a rare fish tale

Monday, March 22, 2021

News Release- Queen’s University researchers Peter Davies and Laurie Graham have published a study in Trends in Genetics reporting a gene that crossed the “species barrier”. The study, Horizontal Gene Transfer in Vertebrates: A Fishy Tale looks specifically at new evidence proving the direction of transfer was from herring to smelt.

Just over 10 years ago, unexpected similarities between the antifreeze protein (AFP) genes of herring and smelt led the authors to propose that the AFP gene had jumped between these different species of fish. AFPs bind to ice crystals to stop them from growing and protect fish from freezing when they swim in icy water. Just as antibiotic resistance offers a survival advantage to bacteria (which can readily swap genes), the antifreeze protein gene would have offered the same to a fish encountering icy seas as the Earth entered the last ice age. While a variety of fishes slowly evolved different kinds of AFPs, the smelt short circuited this lengthy process when it received the readymade AFP gene from a herring.

This research shows a unique example of direct vertebrate to vertebrate transmission of a useful gene, analogous to genetic modifications that can be carried out in a laboratory.

How did the gene jump the species barrier? For most fish, fertilization occurs externally in water that is contaminated with the DNA of many organisms. The authors suggest that the antifreeze gene piggy-backed into the fish egg on the sperm during fertilization. They say it will be worth examining other fishes for additional examples of horizontal gene transfer.

The study appears in the March issue of the journal Trends in Genetics and is also available online and from PubMed.

 A video by Thomas Hansen that expands on the story, is available here.

 

Quotes

It was just over 10 years ago that Dr. Graham and I got the first hints that an antifreeze protein gene had ‘jumped’ the species barrier between fish that included the herring and smelt. Bacteria readily swap genes, which can be a beneficial to their survival, when these pieces of DNA lead to antibiotic resistance. However, if a gene is to be directly passed between fish, it would have to be incorporated into their reproductive cells. - Peter Davies, Professor, Biomedical and Molecular Sciences, Queen’s University

“What happened in nature is similar to what could have been achieved by genetically engineering the fish in a lab.”- Peter Davies, Professor, Biomedical and Molecular Sciences, Queen’s University

“Now that the herring genome has been sequenced and is available on-line, I was able to read the DNA and confirm that this beneficial gene has been passed from the herring to the smelts. Reading the herring genome sequence also showed that this gene did not start out in the herring but was transferred in from another fish, before a copy was later passed on to the smelt.”- Laurie Graham, Professor, Biomedical and Molecular Sciences, Queen’s University

 

Links
Trends in Genetics

PubMed

 

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