Honeybee genetics fight pathogens

Scientists look at how to use insect’s antiviral response to control viruses and parasites 
in crops and bee colonies

Honeybees use different sets of genes to fight different viruses, bacteria and pathogens.

According to researchers at Pennsylvania State University, these genes are regulated by two distinct mechanisms. Understanding how they work could help scientists develop treatments designed for specific infections.

“Honey bees, as with many other organisms, have specific molecules that will recognize individual pathogens,” said David Galbraith, a graduate student in entomology.

“Once these molecules identify the type of pathogen, a set of genes will then be turned on, resulting in an appropriate response, whether that be antiviral, antibacterial, etc.”

Pests, parasites, and weather conditions continually challenge honeybees. The insects face more than 20 different kinds of viruses. Several of them, such as the varroa virus, are linked to colony collapses.

According to Christina Grozinger, director of the Penn State Center for Pollinator Research, beekeepers lose an average of 30 percent of their colonies every winter and an average of 25 percent in the summer.

To understand viral infections, researchers wanted to know which genes increased or decreased their activity in response to a pathogen.

Viruses are microscopic organisms that consist of genetic material (RNA) contained in a protein coat. Unable to live independently, they multiply inside a living host, like a bee.

In bees, the virus goes through its life cycle, but at a critical stage the bee’s genes recognize the invader. Its immune system destroys the virus by interfering with the virus’s RNA and fragmenting it into pieces.

“The RNA interference (RNAi) pathway is a primitive antiviral re-sponse that has also been exploited as a laboratory technique to control gene expression in a wide variety of organisms,” said Galbraith.

According to Grozinger, scientists and beekeepers are interested in finding ways to use RNAi to control viruses and parasites in agricultural crops and in honeybee colonies.

Honeybees are genetically equal at birth, but as they take on specific roles in life their behaviour and physical makeup are changed. These modifications include the addition of chemical “tags” in the form of methyl molecules that alter the way a gene is expressed.

“DNA methylation can change expression of genes and it used to be thought that it was a “permanent” change that would be maintained as cells divide,” said Gailbraith.

“But there is increasing evidence that DNA methylation can change rapidly in response to environmental and physiological changes.”

She said researchers found there may be two genomic response pathways to viral infection.

Galbraith said that current technology to alter DNA methylation patterns is spotty and it will take further investigation.

“The next phase of our research is to figure out if we can safely alter DNA methylation in a manner that makes the bees more resistant to viruses,” he said. “There has been some research into using RNAi technology to treat honeybees to reduce viral infections, but this technology needs more research before it can be used commercially.”

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