Science Interviews


Sun, 21st Jun 2009

Transgenic Plants

Professor Jonathan Jones, The Sainsbury Laboratory, Norwich

Listen Now    Download as mp3 from the show The Future of our Food

Chris -   Now, one of the things that farmers have to do is to combat the problem of plant pests.  And at the moment, they tend to do that in one way which is by using chemicals to treat the problem.  But one alternative could be the use of genetic techniques.  In other words, we could take genes from one plant or perhaps even a totally different species that knows how to destroy a pathogen, give it to a plant and that plant then has the ability to ward off that pathogen chemically, but without farm having to add additional chemicals.  How do we do this and why is it any better than existing techniques?  To tell us, here's Professor Jonathan Jones, he's based at the Sainsbury Laboratory in Norwich.  Hi, Jonathan.

Jonathan -  Hello there.

Chris -  And welcome to the Naked Scientists.  First of all, if you would, just tell us, how do you actually make a genetically modified plant?

Rice PlantJonathan -  Well, a plant carries 50,000 genes or so, and the idea was to put in a gene or two that confers a useful new trait.  And to do that, you take advantage of a bacterium called agri-bacterium which naturally causes galls on a number of crops, particularly grapevine but a number of others too.  And it does this by introducing DNA into the cells of that plant, that make the plant more conducive to the growth of bacterium.  And what scientists have done over the last 30 years actually, is to understand this process, break it down into components, and then use their knowledge of the DNA  that transfers the DNA into the plant cell and get rid of the genes that make the plant cell do a number of growth characteristics that are not good for the plant.  And then you can put in genes that confer properties that would be advantageous for the crop and then what you do, is you incubate the plant cells with the bacteria and then you select for those plant cells that receive the genes that you're interested in and then at the end, you get a plant back from that, that has 50,000 genes it started with and has a couple of new genes as well.

Chris -  What sorts of things have scientists done, in terms of actually making functional crops that will be useful?  What sorts of genes have they inserted to enable crops to do novel things?

Jonathan -  The first thing that was done was to help farmers control weeds.  And so, in the absence of weed control, you can lose 30% or 40% of your yield.  I can go into my back garden and do some hoeing to control weeds, but they're constant problem, as anyone who has ever grown any crops or allotment will know.  And if you go out in a 50 hectare field or whatever to control weeds, then there's no alternative really to herbicides.  And the problem is that many herbicides are damaging to water courses, they're quite persistent.  And so, the herbicides that were being used a lot in the '70s. there's a strong incentive to replace them with something that was less persistent.  And the main one that was adopted worldwide was the glyphosate resistance trait.  So, glyphosate is a very good herbicide but it kills all known plants including the crop.  And so, what was done was to engineer in a gene that meant that the crop survived the glyphosate and so, the weeds were better controlled.  And glyphosate is inactivated quickly in the soil so, it's less damaging way to control weeds than methods that it replaced.  Subsequent to that, then there was an insect control.  So there were proteins that are toxic to larvae of moths and butterflies such as the boll weevil, such as the corn rootworm, such as corn stem and cob worm.  And so, you can engineer the plant to make a protein that kills the insect and that's better than the technology it replaced which was applying insecticides.

Chris -  Can I ask just you something about the practice of making a genetically modified plant because…

Jonathan -  Yes.

Chris -  …when you actually put the foreign gene from one organism or one plant species into another to give it that resistance, do you know where into the plant's genetic material that had integration, that insertion has occurred or is it to all intents and purposes random?

In an effort to reduce corn stem-borer infestations, corporate and public researchers partner to develop local [transgenic] Bt (Bacillus thuringiensis) corn varieties suitable for Kenya.onathan -  Where it goes in any particular transformation event is currently unpredictable but you can then find out were it went.  Because what's actually done to bring some of the commercial variety is to make hundreds of transformation events or even thousands and select one that has no, shall we say, collateral damage in terms of the performance of the plant and then characterize where it went in very thoroughly.  So, anything that's on the market is very well defined, where the gene went in.  There are new technologies becoming available to put DNA in at a defined position and currently, that's experimental but it looks promising.  But no crops resulting from that technology are yet anywhere near commercialization.

Chris -  Because if I might ask you very briefly, just to give us the answer to this, which is that, if you got to say, a gene in a plant which is not essential for that plant to grow, but it does for instance remove a toxin that might be bad for us if we ate the plant, but it doesn't really harm the plant, if you put your new gene into the plant and it deactivated that gene that gets rid of that toxin or it makes the plant, so it's more vulnerable to something else, it might grow a mold which is bad for us if we eat it.  How do we know that hasn't happen and that therefore, we haven't had some kind of knock-on effect to the safety of the crop?

Jonathan -  Well, when I said that there's a lot of transformants was made in any such experiment which then screened for their properties or whether there's any collateral damage, that's the kind of collateral damage that people look for.  There'll be experimental acres, you know, large area devoted to this trialed crop before it hits the public and if anything like that would happen, it would become clear at an early stage before it reached the market.

Chris -  And we will be talking about organic farming in just a second.  Why is this better than organic techniques?

Jonathan -  I mean, the problem with organic farming is that yields are low.  Lower than conventional agriculture.  It is true that they cause less collateral damage, there's less risk of nitrogen run off into water courses, there is certainly no insecticides applied, although that you use copper sulfate to control late blight in potatoes.  But the main problem is yield.  By 2030, we're going to need to double yield because of the growing population and because of increasing demand throughout the world for more meat in the diet.  And to double yield it is going to be tough ask and I don't think it is going to happen with organic agriculture.

Chris -  So basically, we need the technology that you're coming out with.


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