>Bi-directional RNA mobilization may lead to dual co-evolution
of host and virus. Expression of viral sequences from the
host genome is probably an infrequent event prone to
deterioration. However, when expressible, it may lead to the
appearance of a new host phenotype. [Comment: I mention this because it
created quite a buzz at the time. Where did this discovery lead to?]
Good question Pete! I've been working with Dr. Maori, and we recently
spent some time with Dr. Maria-Carla Saleh (from the Institut Pasteur,
where considerable research on this subject has taken place)*. Much
progress has now been made on our understanding of the endogenization (or
horizontal gene transfer) of viral sequences into the genomes of
vertebrates, plants, arthropods, and fungi.
We now know that this is a common natural evolutionary occurrence, with the
result that most (if not all) species could be considered as GMOs. It
appears that endogenization of part of the viral genome often offers
adaptive benefit to the host population. Goic and Saleh explain:
" it is tempting to think of viruses as modulators of the ecosystem. For
instance, farmed animals and plants are frequently plagued with
disease-causing or lethal virus infections. The lack of heterogeneity in
the host population, together with the overcrowding of individuals, may
create conditions where the asymptomatic virus can switch to an acute
infection. This infection may then force the appearance of less susceptible
host variants or may reduce the host population to a size that can no
longer support viral transmission or dissemination. In both cases, even
when the acute infection has a cost for some or many individuals, the host
population may gain benefits at the species level."
We beekeepers are witness to this process taking place in the honey bee
since the introduction of varroa, which completely changed the success at
transmission of several viruses (notably DWV, the KBV family, and LSV).
*Goic B, Saleh MC (2012) Living with the enemy: viral persistent infections
from a friendly viewpoint. Curr Opin Microbiol. 15(4):531-7. doi:
10.1016/j.mib.2012.06.002.
--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com
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