Recorded: 08 May 2008
Yeah, well, so the original idea was to cover mutations which made Drosophila resistant to one particular virus, an RNA virus, and this was all Luis’ idea, it wasn’t mine, he had the idea and came to me to do it, and very quickly he found strains of Drosophila melanogaster which were very, very resistant to a particular virus and it was exciting. But then within a few weeks, it was clear that this was not due to a mutation because it showed maternal inheritance and just didn’t have the properties of being under genetic control and he showed very quickly that the resistance is caused by a bacterium, by infection of Drosophila. So there’s a ubiquitous bacterium called Wolbachia, which you’ve probably heard of Wolbachia. Wolbachia is an intracellular bacterium, so it’s a raquetts serum. Its rather similar to the, rather it’s genetically similar to the causative organism of typhus in humans. And Wolbachia is found in natural populations of most insects, in fact most arthropods, crustacea and also some nematodes. Um it’s, and Wolbachia is very cunning because it is intracellular and it’s transmitted maternally, it’s transmitted through the egg. So it manipulates the, it frequently manipulates its host organism so that it optimizes, optimizes its own transmission. So very often Wolbachia infection will lead to a killing of male progenies or the progeny of female, which transmit the bacterium, males don’t. So it’s very clever and so it’s been a bit of a mystery why, well it still is, why Wolbachia is so ubiquitous and just why it is maintained in populations of species and so prevalent and it turns out in Drosophila, we don’t know if this is going to be true for other insects, if you are infected by Wolbachia you are very, very resistant to the pathogenic effects of RNA viruses. But that was totally unexpected, yeah. That’s when science really progresses, when you, if you find something you don’t expect.
Yeah, well the one we work with is called Drosophila C. Virus, DCV, it’s a negative strand RNA virus, it’s fairly closely related to Polio virus, but it’s actually a different family, the structure of its genome is slightly different and it’s a ubiquitous pathogen in Drosophila, it’s not, I mean it’s very widespread and, but mostly the levels of infection, I think, are fairly low. But, if you inject it into naive flies they die in few days unless they’ve got Wolbachia, in which case they don’t, they live. We don’t understand the mechanism. The problem is, you can’t, since Wolbachia is intracellular parasite, and we can’t culture it outside the cell, it’s actually quite tough to get at it. We’ve got some ideas, but we’ll see.
Yeah, yes, we’d like to look at other insects, and, but we haven’t done that, yes. It could potentially be quite important because…there are some insect diseases of viruses which are economically important, particularly in honey bees, for example. We’d like to get a collaboration together with some bee people to see whether or not we cant protect honey bees, because that, Wolbachia itself, it can be benign, and sometimes it does often cause these weird sex ratio affects or forms of reproductive vaccination between infected and uninfected strains, but it can be benign. I mean it’s possible that this discovery could be exploited, yeah, but...
Well Wolbachia itself can cause, I mean for example, in many beetles, Wolbachia if you cross a, an infected male and an uninfected female then the male progeny die, the males die, so you get a sex ratio effect.
Michael Ashburner, a leader in Drosophila Genetics and bioinformatics, received his B.A. (1964), M.A. (1968), Ph.D. (1968) and Sc.D. (1978) from the University of Cambridge, where he is currently professor of Biology in the Department of Genetics and a Professional Fellow of Churchill College.
He has been the joint head of European Bioinformatics Institute (EBI), of the European Molecular Biology Laboratory (EMBL) and was co-founder of Flybase, the primary online database for Drosophila genetics and molecular biology, the Gene Ontology Consortium, an effort to coordinate biological databases through a defined taxonomy of gene function, and the Crete Meetings, a bi-annual event focusing on the developmental and molecular biology of Drosophila melanogaster.
Among many honors, he is the recipient of the G.J. Mendel Medal (Czech Republic 1998) and the George W. Beadle Medal (Genetics Society of America 1999).