Farmers like genetically engineered (GE) crops because they require less pesticides and fertilizers than conventional crops. This allows farmers to save money, time, and also the environment.
One of the most famous GE technologies, Bt, introduced a gene that makes plants insect-resistant. Plants produce a protein, named Cry, which is toxic for insects but does not affect humans. This technology eliminates the need for indiscriminate fumigation of entire fields.
Bt technology was developed during the 90’s; cleaver as it is, a new technology just down the corner could make it look like a VHS recorder.
RNA interference (RNAi) technology is a tool so precise and accurate that will be more effective and even safer for humans and the environment than first-generation GE insect-resistant crops (1). How does it work?:
CSI viewers and crime-stories’ fans know that DNA fingerprints are so personal that they allow pin-pointing of individuals. Biologists also use DNA sequencing to identify species and families of species, even extinct species.
DNA doesn’t do much work in the cells though; it is more like a DIY book that cells read to know what to do. DNA contains instructions on how to make proteins. Proteins are the real players in the cells.
Proteins do all the work: they convert food into energy and energy into fat stores; they build the cell membranes and defence systems; they even make more proteins*. This is a key point for the new technology. Before protein-making proteins can read instructions encoded in DNA, the instructions need to be transcribed into RNA code. RNA is a molecule closely related to DNA. Proteins that make more proteins read their instructions from RNA.
RNA is neither protein nor DNA; RNA is RNA. It carries the same message as DNA but the message is written in different characters, like books in Greek and English. Taking the analogy further, it would be as if proteins that make proteins could read “English” (RNA) but not “Greek” (DNA).
In 1998 Fire and Mello discovered that there was a second type of RNA (RNAi), an anti sense RNA with instructions written upside down. This RNAi prevented protein workers from reading normal RNA, even causing it to be destroyed. This prevents the building of proteins. In normal circumstances RNAi is used by cells for regulating processes after DNA has been transcribed into RNA and for fighting viruses. Fire and Mello received the Nobel Prize in 2006 for their discovery.
DNA and RNA share important characteristics; they are equally written in a 4 letters code of nucleic acids and are very particular of each species or families of species. For this reason, RNAi could be used to target specific pests leaving any other species untouched. For example, plants could produce an RNAi that selectively kills a nasty insect, such as the corn borer, leaving pollinators completely unharmed (1).
Several universities and companies are now competing to develop and commercialize RNAi GE technology and to deliver an insecticide with a scalpel’s precision.
Read also Kai Kupferschimidt excellent article in Science Magazine VOL 341 p732-3 (You will need a subscription)
You can listen to Science Magazine Podcast about pesticides for free
* To be more precise proteins are built by ribosomes, large and complex cellular machines formed by proteins and rRNA.