Researchers working on RNAi (I've been involved in a couple of projects)
have two big things to address:
1. Delivery
2. Unintended side effects

Several years ago, researchers discovered that double-stranded RNA (dsRNA)
was used by invertebrates and plants to activate a system to both fight
viruses, and to regulate gene expression.  Thus, one could theoretically
use dsRNA to "silence" or "knock down" the expression of a specific gene in
an organism without affecting other gene function.

As it turns out, it's not that simple.  Yes, gene function can be knocked
down, but for some reason, other gene expressions are also affected.  This
came as a surprise to us, based upon Michelle Flenniken's research on dsRNA
and bee viruses.

And then there is the "delivery" issue.  In one large project that both I
and the lead author of the cited paper, Eyal Maori, were involved in, we
just couldn't get enough dsRNA into the plant (and we tried REALLY hard) to
have an effect.  Monsanto, with all their research money, also stumbled
over the same hurdle.  And Monsanto also has the same problem with their
varroa control research--how do you get enough dsRNA into the mite?

And even if you are able to deliver dsRNA into an organism, Maori then asks
the obvious question:   " Interestingly, while the aforementioned examples
provide evidence that some organisms acquire, and are affected by foreign
regulatory RNA, it is still puzzling why would they allow it? This
evolutionary maintained susceptibility to non-self regulatory RNA is
intriguing in light of the fact that the most well-known transmissible RNA
are viruses."

We were more successful getting it into insects via feeding.  Once in the
insect or plant, a protein called RNA-dependent RNA polymerase (RdRP) then
amplifies the number of copies of the dsRNA (simple version).  This
critical amplification allows for a treatment effect resulting from the
introduction of a small amount of dsRNA.  This process works well for fed
dsRNA for virus suppression and at least some gene knockdown (we were
working with mosquitoes).

However, in a recent study in which researchers *injected* DWV dsRNA into
bees, and then introduced the bees into observation hives, those injected
bees still got infected with DWV after a number of days (Title: "Covert
deformed wing virus infections have long-term deleterious effects on
honeybee foraging and survival").

Maori's paper is of great interest, and it is no surprise to me that honey
bees use jelly to pass virus resistance from one bee to another--although
he didn't delve into such transfer via worker-to-worker trophyllaxis.
We're learning a great deal about the molecular biology of bees.  Lots of
new acronyms to learn, but the biology is absolutely fascinating!

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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