(ORDO NEWS) — A deadly virus that infects caterpillars changes the activity of light-related genes to drive insects to the tops of trees, scientists from the China Agricultural University have found. The study was published in the journal Molecular Ecology.
Nucleopolyhedrovirus infect some insects, including caterpillars of the cotton bollworm. Before dying, caterpillars climb to the tops of trees – it is believed that this contributes to a more active spread of the virus. Earlier studies have shown that HearNPV-infected caterpillars gravitate towards light sources.
The researchers placed infected caterpillars in glass tubes and installed a light source at the top, middle, and bottom of the tube. The higher the source was, the higher the infected caterpillars climbed. The control group of healthy caterpillars did not react to light.
Additional experiments with completely blind caterpillars confirmed that it was light that caused the reaction, and not gravity, height, or other factors – unable to recognize the light source, the caterpillars did not react to it.
“Because sunlight illuminates plants from above, positive phototaxis (the ability to navigate and move towards a light source) is likely a reliable mechanism for the death of infected larvae on host plants at high altitude,” the authors of the work noted.
They also studied the genetic differences between infected caterpillars and healthy ones. They found six genes involved in the response to light, the activity of which changed under the influence of the virus. Three of these proved to be the most important.
HaBL for detecting short wavelength light, HaLW for detecting long wavelength light, and TRPL, which converts light into electrical signals. When these genes were turned off in infected caterpillars, the insects were less likely to approach or die near a light source.
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