There’s been recent excitement over the discovery of bornaviruses fixed in the human genome1, 2. Exciting and unexpected as that is, as usual, the insects are way ahead of us. The genome of a parasitoid wasp has poxvirus sequences in it!
Detecting ancient lateral transfers is more problematic. By examining protein domain arrangements in Nasonia relative to other organisms, we uncovered an ancient lateral gene transfer involving Pox viruses, Wolbachia, and Nasonia. Thirteen ANK repeat–bearing proteins encoded in the N. vitripennis genome also contain C-terminal PRANC (Pox proteins repeats of ankyrin–C terminal) domains. This domain was previously only described in Pox viruses, where it is associated with ANK repeats and inhibits the nuclear factor ΚB (NF- ΚB) pathway in mammalian hosts …3
These parasitic wasps are not the same family as the magnificent braconid parasitic wasps that have developed a symbiotic relationship with polydnaviruses (see my posts here and here), and braconids’ incorporation of nudivirus genomes already trumps the bornavirus findings. But still. Poxviruses!
I don’t think we have any functional information on what the Nasiona are doing with the poxvirus genes here, and I know very little about wasp biology, but given that:
- in mammals these genes are inhibitors of the innate immune response,
- the innate immune response is relatively conserved from insects to humans, and
- Braconid wasps use their symbiotic viruses to inhibit their prey’s immune responses,
I wonder if the Nasonia have independently come up with the same idea as Braconids, and incorporated a viral immune evasion molecule to use in their venom to suppress their prey’s immune response to the wasp’s eggs and larvae.
- Original paper in Nature[↩]
- See commentary in the New York Times; the Virology Blog; and Not Exactly Rocket Science[↩]
- The Nasonia Genome Working Group (2010). Functional and Evolutionary Insights from the Genomes of Three Parasitoid Nasonia Species Science, 327 (5963), 343-348 DOI: 10.1126/science.1178028[↩]
This is clearly an interesting finding and I am looking forward to learning what all these viral Ank/PRANC proteins are doing. Here are a few remarks.
First, the poxvial PRANC proteins are not that novel or unusual. Ankyrin repeat proteins are found all over the place, and what the viral people call a PRANC domain is not different from a plain old F-box domain. Admittedly, this particular combination is much more restricted than the individual domains.
In any case, these proteins are probably not a viral invention and have been hijacked from a host genome at one point. As the PRANC proteins are found in different types of poxviruses, this acquisition must have taken place rather early. As far as I know, it has not been formally excluded that the Ank/PRANC proteins were originally a wasp invention and have been acquired by the viruses later (not very likely, though).
In the recent literature, there are reports claiming that poxviral Ank/PRANC proteins work through messing with the Akt pathway. I haven’t read those paper, so I cannot comment on the solidity of these data. However, Akt is not the first pathway I would have thought of and I doubt that this will be the last word on the subject
Hi, Kay. Thanks for the comments. Chris Upton (in Twitter) said that he’s not even sure if entomopox viruses have these PRANC proteins. To make it even harder to figure out, the viral sequences in the wasps apparently come via the Wohlbachia, which is to me even weirder, and I don’t know what they think is happening.
And did you know that some poxvirus genomes contain an endogenous retroviral genome?
Hint taken directly from the Nasonia wikipedia page:
“Nasonia are a genus of small pteromalid parasitoid wasps that sting and lay eggs in the pupae of various flies. The fly species that Nasonia usually parasitize are primarily blowflies and fleshflies..”
See that? They take the machinery from Wolbachia for primer insertion, and they use a cation channel neurotoxin.
“{alpha}-Latrotoxin consists of a conserved N-terminal domain and C-terminal ankyrin-like repeats. ”
For those slow on the uptake, latrotroxin is a spider neurotoxin.
http://en.wikipedia.org/wiki/Alpha-Latrotoxin
Add a few or take away a few of the repeats changes the toxicity.
http://www.jneurosci.org/cgi/content/full/25/44/10188
A publication from 10 years ago on the Entomopoxvirus and gene similarities with mammalian pox viruses:
Virions of Heliothis armigera Entomopoxvirus contain a Homologue of the Vaccinia VP8 Major Core Protein. Rosa Crnov1 and David J. Dall. Virus Genes 19:23-31 (1999).
http://www.springerlink.com/content/kr125p12n53g64q5/gue of the Vaccinia VP8 Major Core Protein