Virus-infected caterpillars become real zombies

Zoological studies have helped to understand the animal Kingdom and the different phenomena that take place there. Recently, a study showed that the caterpillars start to climb towards the sky because of a infection. The disease is caused by the presence of a virus modifying related genes vision and increasing the insect’s attraction to sunlight.

Each time a cotton pod earthworm caterpillar climbs, its tiny body moves incessantly from leaf to leaf. Upon reaching the top of a plant, she finds death. And this is how the virus manages to proliferate rapidly.

This discovery is reported on the Internet in the newspaper Molecular Ecology.

A caterpillar-controlling virus

In reality, this virus affecting the larvae belongs to the family of baculovirus. As Xiaoxia Liu, an entomologist at China Agricultural University in Beijing, points out, these viruses have evolved very well. together with their hosts. Indeed, these baculoviruses are likely to contaminate nearly 800 categories of insects, in particular butterfly larvae day and moths.

As soon as they are affected, the insect hosts manifest the tree crown disease. They feel compelled to climb the trees before succumbing, leaving their contagious remains to the litter of scavengers. According to Liu, the trickery of this virus has been well mastered by scientists for a hundred years. However, the researchers did not know the mode of transformation used to make caterpillars zombies.

Recent analyzes have revealed an increase in the phototaxis in infected caterpillars. Reason for which, they have an attraction for the rays of light. Liu and his collaborators confirmed this conclusion following an experiment on cotton-husk earthworm larvae (Helicoverpa armigera) infected with a bacillus called HearNPV.

A bacillus modifying the ocular genetic heritage

The scientists compared the level of activity of different genes present in the body of each caterpillar, whether infected or not. They discovered in their eyes, 2 opsin genes. It is light-reactive proteins and which are decisive for sight. These turned out more active in the event of a viral infection, in the same way as the TRPL.

Using the gene editing device CRISPR/Cas9 to neutralize the genome of the TRPL and the opsin, the number of insects having been attracted by the light of the box decreased. According to Liu, this is how the virus is able manipulate the genetic structure associated with sight caterpillars.


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