Skip to comments.Ancient Virus Gave Wasps Their Sting
Posted on 02/15/2009 8:07:15 PM PST by neverdem
Parent trap. Parasitic wasps inject caterpillars with a virus to disable their natural defenses and allow wasp larvae to grow within caterpillars' bodies.
Credit: : Image courtesy of Alex Wild/myrmecos.net
By Rachel Zelkowitz
ScienceNOW Daily News
12 February 2009
There's no consent for these surrogate parents. Tens of thousands of wasp species lay their eggs inside caterpillars, injecting toxins that paralyze the hosts and allow their young to feast on the innards with impunity. Researchers have long wondered what exactly these toxins are and where they came from. The answers, a new genetic analysis reveals, have to do with a virus that infected wasps millions of years ago.
The first clue to the nature of the wasp's toxins came in the 1970s. Using electron microscopy, researchers found that they consisted of protein-encased, double-stranded DNA particles that were produced in the wasps' ovaries. Because they resemble viruses, the toxins were christened polydnaviruses.
But the virus classification immediately provoked debate. Genetic analysis revealed that the particles harbored mostly wasp DNA and didn't seem to contain any of the proteins most viruses use to replicate. These two observations led some researchers to argue that the particles were actually "genetic secretions" of the wasp itself rather than an independent virus.
Determined to resolve the debate, entomologist Jean-Michel Drezen of the University of Tours in France and colleagues decoded the first complete sequence of a polydnavirus in 2004. But those results also showed mostly wasp DNA (Science, 8 October 2004, p. 286). So in the new study, Drezen's team looked at DNA from wasp ovaries, in which the polydnaviruses are made. They analyzed DNA from three different wasp species and checked the sequences against those of known insect viruses. In one group of wasps, 22 genes matched those of an ancient family of viruses called nudiviruses, the researchers report tomorrow in Science. Further experiments showed that these genes code for key structural proteins in the wasps' polydnavirus toxins.
What this means, explains Drezen, is that nudiviruses infected wasps a few million years ago and that, over time, the viral DNA fully integrated into the wasp genome. As it currently stands, the wasps need the virus to survive, because the virus helps the insects lay eggs in caterpillars. The virus also needs the wasp to survive, because the virus can only replicate in the wasp's ovaries. The virus cannot replicate inside the caterpillar, because all of its replication machinery is inside the wasp.
The findings provide the most convincing evidence to date that some polydnaviruses descended from a type of nudivirus that infected wasps millions of years ago, says Nancy Beckage, an entomologist at the University of California, Riverside. The researchers could not explain how the second group of polydnaviruses--which didn't contain nudivirus genes--developed. But another kind of insect virus, as yet undiscovered or even extinct, might have infiltrated wasps to create those groups, says James Webb, an entomologist at the University of Kentucky, Lexington.
Learning more about how these viruses work could have clinical applications, says Drezen. The polydnavirus acts as a gene vector, carrying much larger chunks of DNA to the caterpillar than any synthetic gene therapy agent can transport. Thus, studying these viruses could enhance gene-therapy techniques, Drezen says.
Genome Sequence of a Polydnavirus: Insights into Symbiotic Virus Evolution
Science 306 (5694), 286. [DOI: 10.1126/science.1103066]
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Nature News version
Is this how some of Europe’s descendants are immune from the Plague (viral, not bacterial. I think there were several different “Plagues”)
I’m still not sure how but somehow this has got to be Bush’s fault.
Thankfully, Ø-bama will fix this, possibly in the next stimulus bill.
Fascinating, that viruses can integrate into a species’ genetic code. There’s probably examples of this in a lot of other species as well. It may be that viruses are our best friend as well as our most dangerous enemies.
A number of families whose ancestors survived the Black Plague were found to have gene which had a 32 kilobase pair deletion for the CCR5 receptor, IIRC.
BEFORE they got “infected,” how did the wasps lay their eggs?
Happy Birthday, Darwin!
Ummm, the same way they lay them now. They just had a lower survival rate. Of course the caterpillars’ defenses probably hadn’t developed as much yet either.
Could explain evolution better than Darwin does...
Yikes! What a way to die: Paralyzed and eaten from the inside out! Let’s hope no large super-intelligent wasps on some other planet take humans for prey. Stuff of nightmares!
Transposable genetic elements incorporated into viruses have long been known to possess the ability to insert genetic sequences coding for new protiens into the chromosomes of host cells. This can be good or bad of course and it seems to me to be just another potential tool by which mutations can occur within a species of plant or animal.
Thanks neverdem! I knew I had read that somewhere before and even that they think AIDS is a distant cousin to the Plague and someone said “The plague is a bacteria” and I remember reading that only ONE of the plagues were bacterial, some were viral which is why they spread so quickly.
But Europeans (European Americans) didn’t seems to die as quickly and some were even immune to AIDS compared to those in Africa and Arabia and I think they thought it had something to do with that built up immunity in our DNA which is ASTONISHING to me. That we could have an IMMUNITY to a virus worked into our genetic code. How brilliant this world is sometimes!
“perhaps it expands upon and improves it instead.”
probably more correct. It is an interesting notion that genetic code could be transferred via virus and would go a long way towards explaining the lack of transitional fossils since genetic sequences that “took” could produce radically different phenotypes much more rapidly (it would seem).
What is even more amazing is all those people that figure that it all happened by the god of chance.
“chance” has never been that kind to me.
FReepmail me if you want on or off my health and science ping list.
Don't have to be from another planet. Don't have to be so very intelligent either. Democrat poly-ticks!
Definitely the stuff of a B-flick for the SciFi network.
#3...nope, you are sadly mistaken...it is all because of global warming! (sarc)