The study, led by agricultural biotechnologist Neena Mitter at the University of Queensland (UQ), involves the development of BioClay, a spray that makes use of microscopic sheets of clay that contain double-stranded RNA (ribonucleic acid). This chemical is released when a plant is threatened, triggering a process known as RNA interference (RNAi), a natural process that leads to the plant silencing the genes of the harmful virus. The potential in this process is that this plant defense system is highly adaptive, opening the possibility of learning new adaptation methods in the face of disease. Its responses are not one-size-fits-all but tailored to counter each virus that enters its system based on the information it receives from the latter's genome.
Two factors to consider with the success of this experiment include the benefits to cutting out the middle man of the pesticide agents and the financial ease of a single step process for farmers. While commercial RNA sprays do exist on the market, they function by targeting and killing insects, not as in the case of this study, building up a plant's defence.
“In agriculture, the need for new control agents grows each year, driven by demand for greater production, the effects of climate change, community and regulatory demands, and toxicity and pesticide resistance,” Mitter said.
In addition, plant-oriented techniques that have been produced in labs so far last only a few days, this makes them problematic on the market as most farmers operate on slim profit margins and are not viably able to spray crops so frequently as an alternative to pesticide chemical application.
This application of BioClay in their experiments with tobacco plants is especially promising with consideration to the financial aspect of farming practices. Mitter and her team found that a single application of the spray stopped the pepper mild mottle virus from infecting and ruining the crop for 20 days. This is a first instance of researchers achieving such a sustained result.
"Once BioClay is applied, the plant 'thinks' it is being attacked by a disease or pest insect and responds by protecting itself from the targeted pest or disease," explains Mitter. "A single spray of BioClay protects the plant and then degrades, reducing the risk to the environment or human health."
Other factors that make RNAi an attractive solution to commercial crop growers include the fact that firstly, while sprays can easily be tailored to fight new viruses or insect infestations, its use is not limited to disease and pest control. It is hypothesised that this technology could range from helping plants get through prolonged drought conditions, to changing the colours of flowers, and increasing the nutritional value of food crops.
Secondly, compared to developing genetically modified (GMO) crops from scratch, RNAi sprays are potentially far cheaper and less time-intensive to develop. According to a survey conducted by trade association CropLife International, developing new GMO crops could easily cost more than US$100 million and take more than 10 years to develop.
Finally, unlike GMO methods, this experiment represents a new technique that doesn't alter the plant's genome. Thanks to prolonged media coverage and legal regulations efforts in this area have reduced the favourability and viability of many biotech crops.
From an ecological perspective, BioClay and other sprays could act in contrast to the conventional pesticides that do not differentiate between helpful and harmful insects and subsequently lead to the death of many beneficial insects who come into contact with the crop. With RNA sprays, scientists could theoretically refer to DNA data to avoid genetic matches with friendly bugs, such as honeybees.
In reality, however, some scientists have been quick to outline that all of these revolutionary features are harder to manufacture than it sounds since many insect species often share the same important genes.
If this venture is successful and we can implement this technology, a further potential advantage is that it should be less harmful to human health since RNA is broken down quickly by enzymes in the saliva and digestive juices.
With such an impressive list of benefits, it is only a question of how long will it take researchers to prepare BioClay commercial use. A large challenge is the is cost – manufacturing RNA is not yet a cheap process. Guus Bakkeren, a research scientist at Agriculture and Agri-Food Canada, is of the opinion that while the technique could certainly help advance scientific research, it remains too premature to talk of its use in the field.
"In general, these techniques are very valuable for scientific research, especially in cases where the pathogens cannot be easily genetically modified for testing gene functions, such as the obligate biotrophic rust fungi," he says. In the case of large-scale applications, the costs of producing si- or dsRNA molecules keep it from becoming an economically feasible option for now.
On the bright side, biotech startups such as Apse are attempting to lower the production costs of RNA for agricultural applications. If successful, this could turn RNA sprays into a much-needed breakthrough for farmers and developing countries that depend on agriculture for trade.
The results of the study were published in Nature Plants.
Source: University of Queensland