Butterflies, wasps and interspecies gene transfer

The more we look, the more we find that transgenic behavior—moving genetic material between unrelated life forms, is common in nature.

One of the hallmarks of the anti-GMO movement seems to be the argument that it’s unnatural to move, for example, bacterial DNA into plants to make them resistant to certain bug predators.

It not only isn’t unnatural, but it happens all the time in nature.

“Breaching the species barrier,” it’s called. It turns out this barrier is pretty porous.

We’ve reported earlier about naturally transgenic sweet potatoes. 

And we’ve reported on virus DNA movement into human DNA and bacteria DNA into animals. 

New evidence released just last week shows that parasitic wasps have inserted viral DNA into butterfly genomes. The viral DNA turns off portions of the butterfly immune system. 

All of this interspecies trade allows the wasps to insert their eggs into the butterfly caterpillar phase without their being attacked by the butterfly immune systems. Creepy, but that's nature.

Here is the Sept. 17, 2015,paper reporting on that finding. It's in the latest PLOS Genetics and is problematically entitled "Recurrent Domestication by Lepidoptera of Genes from Their Parasites Mediated by Bracoviruses."

The process of moving genetic material between species is called horizontal gene transfer. 

The new paper concludes that while science has assumed that species have needed to reshuffle their own genes to fight off  new threats, in fact,  horizontal gene transfer is “recognized as an important factor in…evolution.”

“We show here that in several lineages, lepidopteran genomes have acquired genes from a bracovirus that is symbiotically used by parasitic wasps to inhibit caterpillar host immune defences,” the paper says.

The research suggests that the wasps initially collected the viral DNA, carried it within their bodies, and then transferred it to the butterflies. They used the viral DNA as a kind of tool kit to allow them to carry out their own life cycles.

And there’s more. It appears that the butterflies have then been able to use the borrowed genes to fight off a virus that can attack them.

“Additionally, we present functional analyses suggesting that some of the acquired genes confer to caterpillars a protection toward baculovirus, a very common pathogen in the field. This phenomenon may have implications for understanding how caterpillars acquire resistance against baculoviruses used in biological control,” the paper says.

 

Evolutionary biologist Louise Johnson, at the British University of Reading, said it’s a fine example of just how adaptive evolution can be.

"This three-way gene shuffle is a particularly clear and clever example: wasps use viruses to attack butterflies, but those viruses have also allowed the butterflies to steal genes from the wasps. 

“It’s clear that the stolen genes are useful to the butterflies, so naturally occurring genetic engineering helps them to survive. 

“From my perspective as an evolutionary biologist, it’s also a perfect illustration of how evolution uses every trick in the book, and the book is bigger than we think,” Johnson said.

© Jan TenBruggencate 2015