A bollworm, which is the target of current research into giving crops genetic defenses against pests. Image: Wikimedia
I regularly use an organic pesticide that's made up of ground fossils. It resembles flour more than anything, but, to a tiny beetle, it’s a sea of broken glass, the fine shards of silicon slicing up insect shells like soft flesh. The afflicted bugs die, of course, and the survivors make a point of taking the long way around my Swiss chard. It's amazingly brutal-sounding, really; imagine that at a human scale: broken glass and razor blades falling from the stratosphere in dense, high-velocity clouds. Rough.
It’s a clever way to get rid of some beetles, but it’s crude and basically takes out anything moving and tiny. That’s OK for the couple of acres I have, but hundreds or thousands of acres takes something a bit more sophisticated. Big fields become their own ecosystems, with their own cycles and feedbacks, and the “everything that moves” strategy isn’t good for anything in that context, including the corn or soybeans or cotton that you’re trying to protect.
Even brute-force chemical pesticides have targeting power, and the world is loaded with genetically modified plants that can act as their own deterrents. These are "Bt" plants, crops engineered to produce a certain bacteria that, once consumed by certain herbivorous insects, becomes toxic and, well, you know. Doom. This is a pretty huge thing in global agriculture, but it’s just one, fairly inflexible thing. Agricultural demand is poised to go nuclear in the coming years, and that means a need for more and better tools.
Which shouldn't be more and better chemicals to spray from airplanes. As you might guess, it probably means better genetic engineering of crops. At the pesticide frontier is a totally fascinating and, in this context, vaguely ominous thing called RNAi. It's basically a way to silence certain sequences in a target’s genes.
One way to picture how it works is to imagine an RNAi technique targeting the parts of the human genome that tell your body to make white blood cells. A certain kind of RNA storms in, slices up your genes, and, hey look, no white blood cells. So it’s a very powerful technology in a lot of different fields. (I posted something about it on Facebook last night, and an HIV researcher friend immediately chimed in with a “w00T RNAi.”)
The approximate land area covered by the United States' three major crops. Blue: soybeans; red: cotton; green: corn.
There are three projects looking at RNAi’s potential in agriculture currently underway. They're all different, but the basic idea is to make crops capable of their own RNAi techniques—thus enabling a better defense against pests. So, yes: genetically modified crops are capable of genetically modifying insects.
The most interesting of these are cotton plants that produce double-stranded RNA that suppresses a particular gene in bollworms. It silences the gene that codes for a certain chemical capable of degrading the cotton plants’ natural worm repellant. So, it weakens the worms’ countermeasures against the plant’s already-existing defenses.
However, a paper out in yesterday’s edition of the journal BioScience argues that our current methods of safety testing are unprepared for RNAi technology. Currently, this involves a fairly simple test of toxicity, which is fine for most pesticides that act now and discretely. The paper, written by Jonathan G. Lundgren and Jian J. Duan, argues, however, that we’ve entered into an entirely new realm of unpredictability.
Creating plants that can modify the genome of another organism on their own is a leap past current GMO techniques. A lot of organisms share genes, and with the vast majority of organisms out there not having had their genome sequenced yet, it's impossible to be sure that the bollworm gene being targeted doesn't also show up somewhere else. The chance that crops' RNAi defenses could affect organisms that weren't initially targeted is enough to proceed with caution, which is what Lundgren and Duan argue for.
There are several general centers of concern: silencing the wrong genes in target organisms, silencing the right ones in non-target organisms, overstimulating the immune systems of food consumers with the introduction of tons of weird RNA, and the possibility of killing all gene expression in either target or nontarget organisms by flooding their cells’ RNA machinery with outside RNA. It could just gum up the genetic works entirely. If possible, such an outcome could be very bad.
Here is the pair’s very general conclusion:
The flexibility, adaptability, and demonstrated effectiveness of RNAi technology indicate that it will have an important place in the future of pest management, but these benefits should be viewed in light of the relative environmental risks that the technology poses.
I suspect this will read as absolute doom for the GMO paranoid, rather than a bit of hope for the global food problem (it’s some shading of both). That’s fine. The point is that this is actually a thing to be concerned about, maybe not as a consumer yet, but a warning that we’re treading into unknown waters with RNAi technology and maybe even too fast. We can’t say a thing is safe until we know more what it’s capable of. Ground fossils are indeed brutal, but at least I don't have to keep an eye on successive generations of flea beetles to know I didn't end the world with the stuff.
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