How Enticing Viruses Manipulate Animals

Viruses are ubiquitous to life; they infect everything from the smallest of bacterial cells to the largest of whales. And though these these miniscule pathogens often bring illness, they do not contaminate our bodies out of malice or spite, rather they do so out of necessity. Lacking the prerequisite internal anatomy for self-reproduction, viruses invade the cells of the living as a means of insuring their posterity. They splice their DNA (or RNA) into the nucleus of the host’s cells and effectively subvert its cellular mechanics to meet viral reproductive ends. Hijacked cells are re-programmed by the viruses and become factories dedicated to the task of manufacturing more viruses; viruses which ultimately move on to other victims. In addition to hacking programming codes for the building of replicates, viruses often include sub-routines, or additional programming hacks, that facilitate their journey to new hosts.

By undermining the normal life-processes of the host’s cells, viruses are detriments to health; however, more than just illness can remain in the wake of a virus’s biological sabotage. Sometimes included with the observable symptoms of an ailment are other characteristics of viral infection that serve to promote the spread of disease. The genes that viruses splice into a host cell’s mainframe can code for phenotypes that manipulate unwitting vectors into exposing themselves – purely for the benefit of the virus.

For example, recent work out of Penn State University has shown that a virus common to the squash group of plants does more than just hack a virus-building program into the cells of its vegetative victims - it also includes a program that attracts insects. The cucumber mosaic virus (CMV) infects plants with a gene that causes the plant to synthesize and release chemicals that draw-in hungry aphids. Normally, aphids use their capacity to chemically sense plants as a way to zero-in on healthy and nutritious foodstuffs essential to their survival. By manipulating the aphids’ chemo-sense, the virus’s genes trick the insects into locating and then taking a bite from the diseased leaves of an infected plant. Even though the plant may emit a ‘delicious smell,’ because it has been subjected to disease, it lacks the nutrients needed by the aphids. Luckily for the aphids, after just one bite their tasting-sense overrides their smelling-sense and they’ll bugger-off in search of better food. Unfortunately for other squash plants, the aphids now have a mouthful of CMV virus! Thus, the virus spreads.

The genes of the cucumber mosaic virus can integrate into the DNA of a plant, causing it to produce a chemical compound that manipulates aphids into volunteering their time and services as vectors of disease. This scenario isn’t unique to viruses, plants and insects. Other studies have shown that a similar pathogen to chemo-attractant dynamic exists between sandflies and hamsters; the parasitic protozoa Leishmania causes infected hamsters to produce chemicals that attract sandflies as vectors. And in humans, there is some evidence that Plasmodium falciparum causes more than just malaria, it also hijacks human bodies to produce chemicals that attract more mosquitoes.


Mauck, K., De Moraes, C., & Mescher, M. (2010). Deceptive chemical signals induced by a plant virus attract insect vectors to inferior hosts Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0907191107

Insinuations of Lamarckian Evolution and a Lamenting First Impression

I just had a read of Meet your viral ancestors - how bornaviruses have been infiltrating our genomes for 40 million years over at Not Exactly Rocket Science, and then promptly made a follow-up, though cursory, pass at the associated publication from Nature:

Horie, M., Honda, T., Suzuki, Y., Kobayashi, Y., Daito, T., Oshida, T., Ikuta, K., Jern, P., Gojobori, T., Coffin, J., & Tomonaga, K. (2010). Endogenous non-retroviral RNA virus elements in mammalian genomes Nature, 463 (7277), 84-87 DOI: 10.1038/nature08695



Sine Ed has already accomplished the task of detailing the paper (at the above link), I won’t bother to do so here, rather I’ll just provide my initial, perhaps somewhat imaginative, take on it.

My first impression of the work, once again emphasizing that I sometimes express imaginative tendencies, is that it suggests a Lamarckian process of evolution.

The paper reports on a genera of RNA viruses called ‘bornaviruses’ that seemingly have the capacity to enter, and remain in, in the germlines of their hosts. In the instance of primates, for example, the researchers indicate that bornaviruses have been passed to humans from a lineage stretching back 40-million years. Although the authors don’t make specific reference to Lamarck, they do add to the argument that in addition to demonstrating “functional, albeit weak, evolutionary conservation,” the viruses “may have some function in their host species,” such as being a causative agents of psychiatric disorders, AND EVEN being “a source of genetic novelty” as to become “a new source of genetic innovation”!

So, is the paper saying that the introduction of ACQUIRED CHARACTERS into the germline of a lineage has lead to GENETIC NOVELTIES with the demonstrated ability to translate to the expressed PHENOTYPE of an ANIMAL, thus acting as a source of INNOVATION. That seems to have a tinge of Lamarckism…

Fascinating findings and bold suggestions, but in my interpretation the word ‘innovation’ goes too far in that it implies adaptation, fitness benefit and positive selection. Let’s not forget that Lamarck’s theories also relied on the idea of progression; the belief that evolution advances form towards specific functional goals. The research ‘is what it is;’ but, I can’t help but think that its speculative portions could have written a little differently… I’d be surprised if the ‘tinge’ in this paper isn’t abused by the fundys; there might be a pattern emerging over at Nature…