The Aaas And Genetically Modified Potatoes
Mandy - Tell us exactly what you're up to.
Chris - I'm at the AAAS, which is the American Association for the Advancement of Science, or at least it would be if anyone was here! It was quite ironic that yesterday we were l9ooking for life elsewhere in the universe with Maggie Turnbull from the Carnegie Institution in Washington, and she's narrowed down five stars that she thinks might be good contenders as places to look for life. But we haven't yet discovered any life here in St. Louis!
Mandy - Perhaps they've all been to the moon.
Chris - I think they've gone somewhere but they haven't come here. The thing is that this is in the middle of America and this sets up a big geographical divide between where the people are and where the conference is. This conference is supposed to be reaching out to the general public and telling people what the scientists in America are up to. This is difficult if no-one can come. Another challenge is that it's minus 16 outside today, so it's pretty bracing. The Mississippi River which flows through here is freezing up. Other than that, I'm having a great time. The science is fantastic!
Kat - So what else have you heard out there then Chris?
Chris - One of the things we've heard about has been GM crops. I got talking to a guy called Jossi Shapiro yesterday from Monsanto, the big GM crop giant. They've actually made a form of potato plant which contains a bacterial toxin called BT toxin. He had a wonderful demonstration where he had two potato plants. One was genetically modified and the other one was normal, and both were infested with something called a Colorado beetle. These beetles will demolish potato crops in no time, and he actually talked me through how this demonstration works.
Jossi - We have two potato plants here: one is a traditional or conventional potato plant, while the other is genetically enhanced potato. They're both infested with small Colorado potato beetle larvae, and the larvae are feeding on the two types of plant. On the traditional potato plants, the larvae survive, and we can start to see significant amounts of damage happening where the insects are feeding. On the genetically enhanced potato plant, which is enhanced with a bacillus thuringiensis protein
Chris - In other words, a toxin which is going to kill the beetle.
Jossi - That's right. It's a toxin that's very specific for the order Coleoptera, which are beetles. And so the plant that produces that protein within the cells will kill the insects that feed on it. The good thing about this particular protein is that it has a narrow range of activity, so other insects and all other organisms aside from beetles will not be affected.
Chris - And not toxic to humans?
Jossi - Not at all toxic to humans. It's called BT for Bacillus thuringiensis, which is the bacterium that in nature produces this class of toxin. The BT toxins have been used for about 60 years or more as foliar applied insecticides and have a history of safe usage.
Chris - And how did you actually get the plants to make the toxin? How do you do that?
Jossi - Well it's through molecular biology techniques. We can insert genes and the genetic elements that control the expression of genes into the DNA of the plant cells. The plant will then itself start to produce the plant protein that the gene encodes.
Chris - Can you just talk us through the nuts and bolts of how you actually make a GM crop?
Jossi - There are a couple of ways that are commonly used for inserting this particular kind of constructs into plant cells. One is called agrobacterium transformation, and that involves the use of a bacterium that will insert its own DNA naturally into plant cells of the plant that it infects. Those bacteria have been disarmed so that they are not inserting their own DNA but rather inserting the DNA of interest. The other way is to do it through what's known as the biolistic method. This is a means of bombarding DNA with small pellets that are coded with the genes of interest and thereby inserting the DNA sequence of the construct into the DNA of the plant.
Chris - What about the spread of the gene to other plant in nature? Is that a risk?
Jossi - Well with something like potato it's not a risk because potato is typically not grown to flower. Potato is typically propagated asexually or by pieces of potato. The flow of pollen is not a risk. With other crops there may be some concerns, and so that is something that needs to be studied and remedied in one way or another.
Chris - In the context of the potato pest, how much could this save somebody in the Third World growing potatoes if they were succumbing to pests like this?
Jossi - These Colorado potato beetles are particularly voracious feeders, and as you can see, the damage that has been done to this plant has happened in a relatively short span of time just this afternoon. If we were to come back here tomorrow, these insects will have continued to feed. By the time this conference is over, this plant will no longer have any leaves or have any chance of making a potato. In many cases, such as with subsistence farmers who would not maybe have the means to apply pesticides, it may make the difference between having a potato crop and not having a potato crop at all.