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Published on 01/27/25

CAES researchers study how parasitic wasps use ancient viruses to ensure survival

By Maria M. Lameiras
A tiny wasp stings a white caterpillar larva to lay its eggs.
Braconid wasps use a class of viruses called bracoviruses that can hijack the cells of their hosts without destroying them, expressing genes important to the survival and development of the wasp’s offspring while it feeds on the live host. (Photo by Jena Johnson, UGA Department of Entomology) 

Supported by a $1.1 million award from the National Science Foundation, University of Georgia entomologists Gaelen Burke and Michael Strand are seeking answers about how parasitic wasp biology has developed to use viruses passed down from parent to offspring to ensure survival.

Scientists have been able to trace the relationship between the wasps and their viruses back 100 million years. Today about 55,000 types of wasps carry these types of inherited viruses.

Exploring the ancient relationship between parasitic wasps and viruses

These viral genes that are now part of the genetic makeup of the insect and the viruses are important for helping the wasps to parasitize other host insects. The viral genes in the wasp are dormant until they are “switched on” during their development. Burke and Strand will test their theory that the virus has lost the ability to control its own replication and that wasp processes are involved in controlling the activation of the virus.

“It looks like the wasps are controlling the activation of these viral genes to make the virus. The grant involves determining how those genes are controlled by the wasp,” said Burke, an associate professor in the Department of Entomology in the College of Agricultural and Environmental Sciences.

One of the study’s aims is to look at external mechanisms that could be involved in activating these viral genes, including hormones, as well as examining intracellular mechanisms to determine how the viral genes are activated.

In previous research, Burke’s lab found that tiny parasitic braconid wasps have evolved to make virus genes that function to suppress the immune response in the host insect. Endogenous viruses are the genetic remnants of ancient viral infections that are present in the genome of a host. These virus genes can produce infectious virus particles known as domesticated endogenous viruses, also known as DEVs.

A woman with shoulder-length brown hair, glasses a black shirt and an orange cheetah print scarf smiles at the camera
Gaelen Burke (Photo by Andrew Davis Tucker)

How viral genes help parasitic wasps ensure offspring survival

Braconid wasps use a class of viruses called bracoviruses that can hijack the cells of their hosts without destroying them, expressing genes important to the survival and development of the wasp’s offspring while it feeds on the live host.

Typical viruses invade cells for the sole purpose of replicating themselves, destroying the cells in the process. Unlike typical viruses, domesticated endogenous viruses disable the host insects’ defenses while keeping them alive as a food source for their offspring, killing the host insect.

Previous studies have determined that the replication of the virus in the wasps is limited to specialized calyx cells in the ovaries. These cells develop during the wasp’s pupal stage. As the wasp matures, the virus replicates in the calyx cells, creating virus particles that contain the genetic material of the virus enclosed in a protective protein coat and an envelope membrane.

These virus particles accumulate in the wasp’s oviducts, creating a suspension of virus called calyx fluid. When the wasp lays an egg into a host, she injects a quantity of virus that infects the host, allowing the wasp’s offspring to successfully develop.

“This novel trait is like a weapon,” said Burke. “Our first step is to try and identify hormones that are related to activating the virus replication. We're looking at a number of hormones, primarily those involved in signaling the wasps to transition from the larval to the pupal stage.” 

Unraveling the mechanisms of virus activation in wasps

A man with light brown hair and horn-rimmed glasses and a lab coat holds a specimen dish in a lab.
H.M. Pulliam Chair Michael Strand (Photo by Andrew Davis Tucker)

Next the team will focus on the cells that produce the viruses and what genes are expressed at the same time as the viral genes to determine candidates for wasp genes that are controlling virus replication and activation, Burke added.

“We plan to manipulate the expression of those genes so we can basically illuminate their activity and test whether particular wasp genes are involved in the process of controlling virus replication,” she said.

Using what they find, the team will compare what they find in the tiny braconid wasps Burke focused on in her research to determine whether similar mechanisms are used to control virus replication in different species of parasitic wasps.

“Is it a different solution to the same problem in each case? We want to see whether they’ve evolved in the same way to serve these similar purposes,” Burke said.

Studies like this one are critical to understanding insect physiology and behavior and the influence these beneficial insects can have on fields including agriculture and medicine.

“In medicine, certain types of therapeutics are delivered using a disabled virus to move a gene into another organism. In effect, these insects have evolved to do the same thing. Understanding how these processes work may inform us about how to design vectors like this that could be used for delivering more complex and sophisticated payloads,” said Strand, H.M Pulliam Chair at CAES.

Maria M. Lameiras is a managing editor with the University of Georgia College of Agricultural and Environmental Sciences.