If you wanted to, say, turn a red pepper yellow, you have a few options. You could directly tinker with with the plant's genetic code, tweaking the genes that control its colour. Or, perhaps, you could just mist the plant with a spray that changes its gene expression without altering its genetics.
A team at the University of Queensland in Australia has just published the results of a study in which they successfully used a "gene-silencing spray" to protect tobacco plants from a virus for 20 days with a single application. Its creators hope that the spray might lead to more environmentally-friendly crop production. But the potential applications for such technology are wide-ranging, from conferring temporary drought resistance to making plants more nutritious to protecting them from disease. All of this, in theory, can be accomplished without turning the plants into GMOs.
Gene-silencing sprays work through the process of "RNA interference". They don't actually change a plant's DNA. Instead, they exploit a natural cellular defence system to temporarily shut down a specific gene. When a virus invades cells, the cells cut up some of the invader's RNA, making short pieces of double-stranded RNA that they use to recognise that virus in the future. Double-stranded RNA is a signal to attack. Scientists have now figured out that if they design double-stranded RNA that corresponds to a plant's own genes, those genes will be attacked like invaders, and temporarily turned off.
Gene sprays have only been around for a few years, but already, companies like Monsanto are investing big. Last week, the ag giant announced that a spray targeting varroa mites, which impact the health of honey bees, is now in the final stages of development. The speculative technology remains highly expensive, and its full impacts are not yet well-understood.
For now, perhaps the most interesting question surrounding gene-silencing sprays is whether they will challenge our notion of a GMO. If you change a plant's genetic expression without altering its DNA, has it been "modified"? Is it still "natural"?