“Gene silencing” is one of the hottest topics in science these days. It is the “switching off” of a gene by a mechanism other than genetic modification and is related to epigenetics, the regulation of genes through environmental factors. A gene that would be expressed (turned on) under normal circumstances is in essence switched off via gene silencing.
Recall that the instructions for all life processes in plants and animals are found in the double-helix molecule, deoxyribonucleic acid (DNA). The DNA is a template from which ribonucleic acid (RNA), often called messenger RNA, is formed. An enzyme, RNA polymerase delivers (transcribes) the DNA’s information onto RNA, stimulating genes to turn on or “express” themselves, usually by producing certain proteins, the chemical building blocks of life. If the message is not delivered, the gene is not turned on. In summary, the life process that is supposed to occur never begins, because the proper message is not received. The DNA genetic information has been “silenced.”
RNA interference (RNAi) is a major cause of gene silencing in organisms. It is naturally occurring and often transient. The term was coined by two scientists, who were awarded Nobel Prize in Physiology or Medicine in 2006. The work of Craig C. Mello and Andrew Fire capped a long history in genetic analysis in plants and other organisms investigating genetic expression and suppression. Their study of RNAi in nematodes (round worms) revealed a mechanism responsible for gene-silencing. The exact way RNAi works is complex, but begins when double-stranded RNA is created, then introduced into a cell, which recognizes it as somewhat of a foreign substance, and this activates RNAi.
The ability to silence genes brings to the table huge possibilities in all realms of genetic investigation. RNA interference is a vital part of the immune response to viruses and other foreign genetic material, especially in plants. This brings into focus the role of viruses in honey bees health. There has been relatively little work on honey bee viruses by scientists over the years. They are not easy to detect, and even if there was any evidence viruses were doing harm to honey bee colonies, there were few if any treatment options.
Virus detection is becoming revolutionized via new technologies like RT-PCR assay and the Integrated Virus Detection System (IVDS). We can now look at the latter topic, what to do about viral infections after they are detected, with a fresh eye thanks to efforts of scientists looking at possibilities using RNAi. Viruses produce their own messenger RNA, which hijacks the host’s cell mechanics to replicate the virus instead of the original organism or host. If this can be interfered with via RNAi, the viral RNA no longer can do its job. Because the genome of viruses is shorter and less complicated than other organisms, it becomes relatively easier to get their DNA sequenced.
A pioneer firm in developing RNAi is a company called Beeologics. The first product it attempted to bring to market was Remebee®, which was designed to protect honey bees from Israeli acute paralysis virus (IAPV), It was given wide publicity at the World Apicultural Congress in Melbourne, Australia (Apimondia 2007) as being strongly correlated with CCD. Remebee® was advertised as the the foundation for the development of a comprehensive RNAi based anti viral agent for a series of known bee viruses. A recent paper examines this in some detail. Although viruses are a logical target, perhaps the most important organism that RNAi might target is the Varroa mite.
Beeologics was sold to Monsanto. Unfortunately, the future of Remebee® appears to be in doubt as the company shifts its focus from viral to Varroa mite control using RNAi. Monsanto was recently purchased by Bayer, which provides less opportunity for this technology to go further, although it pulled at least one regulator into the fray, considered by some a “crazy bet.” However, the technology is now being examined by others attempting to find the appropriate “holes in the mite’s armor.” See more about RNAi and Beeologics here. Recently, an outfit named Greenlight Biosciences has acquired the technology from Bayer.
