(ORDO NEWS) — It sounds like the plot of a horror movie, but in the world of insects, this happens more often than you think: viruses take over the bodies of their hosts and lead them to death so that the pathogen can more easily spread to other victims.
It sounds like the plot of a horror movie, but in the world of insects, this happens more often than you think: viruses take over the bodies of their hosts and lead them to death so that the pathogen can more easily spread to other victims.
Scientists believe that in fact, similar cases have been happening for hundreds of millions of years, and new research is shedding light on this issue.
Scientists talked about the strange strategy of a group of viruses that infect insects. They are known as nucleopolyhedrovirus (NPVs), and their victims are caterpillars of the cotton bollworm (Helicoverpa armigera).
Researchers have been watching for a century as the virus drives its caterpillar hosts to the top of the plant before dying, while the more natural behavior for caterpillars to pupate is to descend lower.
But now we have a more detailed understanding of the mechanism behind this “treetop disease.” As it turned out, this behavior of the virus is associated with phototaxis, the natural attraction of living organisms to light.
How the virus controls the host
IN a new study , scientists at China Agricultural University conducted a series of experiments with cotton bollworm caterpillars and a variant of NPV called HearNPV.
Previous research suggested that HearNPV-infected caterpillars gravitated toward light sources, and new work has confirmed this with LED lights, glass tubes, and a climbing net.
At the top of the grid, the infected insects always died, but the higher the light, the higher they rose before dying – being, in fact, already half dead.
Further testing with light in different positions confirmed that the caterpillars were attracted to the light rather than any reaction to gravity or elevation, and that their vision was in fact being used against them: blind H. armigera were not exposed to the same degree of HearNPV.
How all these acrobatic tricks help the virus is not entirely clear. But if the caterpillars die off at the tops of the plants, that seems to give the host virus more room to spread further, whether it’s being carried by the wind or the chance of the caterpillar being eaten by a predator.
“Because sunlight hits plants from above, positive phototaxis is likely a reliable mechanism for killing infected larvae at high altitudes on host plants,” the researchers write.
Interesting differences were also found in the genomes of infected and uninfected caterpillars. The scientists found six genes involved in the response to light that were expressed differently when the HearNPV virus established itself in the body.
Apparently, nucleopolyhedrovirus capture insects’ natural attraction to light and use it against them.
The next question, which remains to be explored, is no less interesting: how exactly does a virus manage to manipulate individual genes so precisely, and can human viruses do the same? Is the zombie virus far from just a figment of the fantasy of horror writers?
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