Honey bees are an important honey producer worldwide. But most importantly they are a pollinator that if did not exist would cause certain foods to cease to exists. Sadly, a lot of factors are causing a decrease in their numbers.
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RNA Modifications
A superstar among bee parasites and pathogens is a mite known as Varroa destructor that feeds on bee fetuses and also functions as a vector (among others) for the deformed wing virus (DWV) another bee scourge. Currently, the main weapon against the mites is using acaricidal substances but those have a big problem. Varroa is evolving resistance against them. But maybe better times are upon us as Sean P. Leonard and his colleagues developed a weapon that targets both the mentioned buggers at the same time.
Eukaryotic organisms have a defense system inside their cells that protects them against foreign RNA (mostly RNA) called RNA interference (RNAi). It works thanks to an enzyme called Dicer that seizes the foreign RNA and chops it into parts long just roughly 21 bases called small interfering RNA (siRNA). These are then loaded onto a protein-based RNA-induced silencing complex (RISC) where one of the two strains is removed while the other functions as a matrix to find complementary RNA. Once such RNA is found in the cell it is split and it cannot work as genetic information anymore. But the RNAi technique is used by the cell to post-transcribe-regulate its genes – in other words, to prevent the creation of a protein after a gene that has already been inscribed into mRNA.
RNAi is used as a tool in molecular biology if you want to turn off a certain gene without destroying it to figure out what exactly it does. But you need a lot of dsRNA to do this as a bee treatment. And dsRNA is expensive and doesn't last long. Another potential problem is getting it into the cell in large enough numbers.
Killing Parasites
This is why scientists took a betaproteobacteria Snodgrassella alvi as a helper. It lives in the bee intestines and the scientists put a modified plasmid – a circular DNA molecule – into it. The bacteria were then able to make dsRNA inside the intestines of the bees. The plasmid included either a part of the Varroa destructor genes, genes from the DWV, or genes for the favorite fluorescent jellyfish protein (GFP) – that was used purely for control.
During the experiment, the researchers first fed the bees with the plasmid bacteria and after some time they infected them with the virus. While the control bees that had the GFP bacteria in them died similarly to bees that had no extra bacteria the bees that were fed the bacteria that carried the anti-viral plasmid were doing much better. Similarly, encouraging results came from the experiments with Varroa as the mites on bees with a bacteria that carried a plasmid with the mites DNA sequences died faster than those in control groups. And this defense does nothing bad to the bees.
So the method works. And another of its benefits is the fact that bees – as social animals – live in large colonies and do a lot of mutual feeding and cleaning so they will naturally spread the modified bacteria among each other. But the authors warn that the journey towards the practical use of the modified bacteria is long and a lot of work needs to be done. There will need to be more verification on how the bacteria transfer between the bees and hives, increase the dsRNA transfer efficiency, etc.
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