Could this cause an apocalyptic worldwide famine if applied to plants that form large parts of human food supply (e.g. by terrorists, rogue states, or as part of the "destruction" phase of a mutually assured destruction)?
Probably not much more than current crop seeds do, insofar as large volumes of crops are already highly homogenous GMO breeds. I think this technique will probably just be a better mousetrap for GMO breeding.
It'd be easily detectable-- any phenotypic differences would present themselves in the first generation. Unless the rogue actors were able to add gene drive genetics to a wide swath of a plant's population in a short amount of time, this doesn't seem a tangible threat.
I guess the question is: How do we target them? We don't really think about it much, but there are a lot of methods of horizontal gene transfer even for larger animals (viruses, inter-"species" breeding). How do we make sure these extra potent genes stay in the intended organisms lines?
Is CRISPR-driven homozygosity more likely to transfer between species than any other? I suspect not. Would it be a problem if several different quasi-species of mosquito lost the potential to incubate malaria? Again, no.
The thing to remember is that wild populations are still subject to selective pressure, even with "driven" genes. If a gene is introduced that makes an individual incapable of reproduction, that will have no long-term effect. Even if the handicapped genetics can be spread widely through the population, it will disappear within a generation, while non-handicapped genetics will thrive. The trick will be to introduce changes that are benign enough in survival terms to make it to the point of fertilization. At that point the driven homozygosity will pitch in.
One could imagine a change that was subtle enough to survive but severe enough that a population could get pushed out of its ecological niche. That's a good reason to try this on pests rather than e.g. endangered megafauna, at least until the consequences are better understood.
> Would it be a problem if several different quasi-species of mosquito lost the potential to incubate malaria?
Yes. There is a reasonable chance that may go very badly. Malaria exists within a very specific niche inside the mosquito. It has risen to the top of the pyramid to establish dominance there. Knocking it from the pyramid, removing malaria from the environment that is the inside of the mosquito, will create a vacuum. Some other disease will rise to occupy the niche. Perhaps it will be harmless, or perhaps it will be worse. But what is true is that whenever a species is artificially removed another rises to take its place.
Do plasmodia compete with each other for insect hosts? Is there some other plasmodium waiting in the wings to wreak deadly havoc, if only it were free from its nemeses P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi? This seems far-fetched, and besides why wouldn't the genetic changes that make mosquitoes unsuitable hosts for the malaria we've had for millennia also make them unsuitable hosts for this new malaria that's going to evolve overnight?
It isn't about only the plasmodia. Insects, all animals, have a an acceptable parasite load. Too many and the host dies. Wild animals live pretty close to that limit. So even if there isn't an exact swap-in replacement, by eliminating malaria some other parasite will step up.
It's possible to extrapolate too much from general biological trends. Considering that the hypothetical "new" protozoan is as likely to target black-bellied bustards as it is to target humans, and that malaria is an awful blight upon humanity, I expect most humans would be pleased to make the exchange.
The only possible difference would be between those varieties that are presently capable of incubating malaria and those that are not. If the driven allele actually works for human purposes, it will work on the former, and have no effect on the latter.
One might imagine a gene the expression of which is modulated by the environment. If this had the effect you fear it would effectively create two species anyway. Either 1) a mosquito population would inhabit a "benign" environment (for the mosquitoes) and individuals could either incubate malaria or not, or 2) a mosquito population would inhabit an environment in which malaria incubation was deleterious to (mosquito) survival. Humanity seeks to modify the first sort of population, and will not affect the second which does not interbreed with it. It's probably a good idea to study the second however!
This article is a decent intro to the concepts and implications of gene drivers. Based on the title, I expected something new; I thought "self-driving genes" would be somehow different than the CRISPR-based developments of late.
