Unraveling soybean cyst nematode resistance
Andrew Bent, Professor
Department of Plant Pathology
UW-Madison College of Agricultural and Life Sciences
Phone (608) 265-3034, (608) 265-3075
For more information:
5:50 - Total time
0:18 - Introduction to a discovery
0:53 - Surprise in the science
1:20 - What to do with the discovery
1:56 - Genetically rare
2:35 - Putting the new knowledge to work
3:06 - Technology used to understand discovery
3:34 - What it was like to make the discovery
5:15 - Tools used in plant research
5:40 - Lead out
Unraveling the mystery of soybean cyst nematode resistance. We’re visiting today with Andrew Bent, Department of Plant Pathology, University of Wisconsin in the College of Agricultural and Life Sciences, Madison, WI and I’m Sevie Kenyon.
Sevie Kenyon: Andrew, can you introduce us to your discovery?
Andrew Bent: Soybean cyst nematode is the biggest disease of soybean worldwide. More soybean yield is lost to soybean cyst nematode than any other disease in most years. There’s a gene that plant breeders have been using for a number of years now, decades, to help the plants resist the soybean cyst nematode but no one’s ever known what those genes encode. I go back and forth between gene and genes because part of our discovery was, to the surprise, that what we thought would be one gene is actually three genes.
Sevie Kenyon: Why is this so surprising?
Andrew Bent: Normally, at a particular place on the chromosome when you have a gene that helps you with something useful, it encodes one protein. In this case, we’ve got a cluster of three genes right next to each other encoding three very different proteins. That’s just not very common in higher multicellular organisms like humans or plants.
Sevie Kenyon: Andrew, what do you think you’re going to do with this discovery?
Andrew Bent: We are going to put it out there for people to try to understand, first of all. Because at the scientific level we’d like to be able to manipulate soybeans for better soybean cyst nematode resistance but we’ve got a ways to go before we can accomplish that at the biotech level. But, our discovery already suggests that you might be able to identify existing soybeans that are out there that have more copies of these genes. That’s part of our discovery.
Sevie Kenyon: Andrew, can you describe where these genes sit in that soybean plant?
Andrew Bent: What’s interesting is where they sit in relation to each other. Not only are there three genes right next to each other but the soybean cyst nematode susceptible soybeans have one copy of the gene and the soybean cyst nematode resistant plants have ten copies of this three-gene block. That’s where the basic genetic scientists are intrigued by this discovery. That you would have a three-gene block and then would be ten copies of that all right next to each other is quite unusual.
Sevie Kenyon: Andrew, do you have a sense for how long it may be before you’re able to completely unravel this mystery and put this information to work?
Andrew Bent: Completely unravel, let’s say, millions of years. No, let’s put it in the human realm of hundreds of years but I think that it may be five or so years and we’ll have a very good understanding of molecular mechanisms which might allow, as I said, more biotechnological approaches to using this to improve disease resistance.
Sevie Kenyon: Andrew, can I get you to describe some of those biotech processes that may be used to implement this knowledge?
Andrew Bent: It’s a natural disease resistance mechanism that’s already in soybeans. So what we would try to do would be [to] make it work a little bit better, possibly by having the proteins expressed at a higher level and possibly by changing the amino acid sequence of those proteins just a little bit to tweak their activity so they maybe function a little bit better.
Sevie Kenyon: Can you give me an idea what it was like to make this finding?
Andrew Bent: Well, it was, first of all, a lot of hard work by a number of people without a whole lot of reward for multiple years. Then, of course, as it all starts to fall into place you say, “Oh. Of course this makes sense,” and it’s extremely exciting.
Sevie Kenyon: How did you discover it?
Andrew Bent: There was a process of silencing the expression of candidate genes in the region. So we had a region of the chromosome with maybe eleven genes and we started reducing the expression of each of those genes individually, using genetic methods and were quite surprised when not just one of the genes seemed to have an impact. You know, if you knocked it out the plants became more susceptible. It was actually three different genes all right next to each other. So that was the first step. From there, we studied the levels of gene expression and we were quite surprised to discover this copy number variation. Two of the most beautiful experiments in the paper that I really love are where you can extend DNA fibers and use fluorescent probes to look at individual fibers and that’s how we were able to count ten copies of this three-gene block. That was really a beautiful and very exciting result, the day we got that. The other experiment was to put all three of the genes together into a gene expression construct and put that into susceptible roots, the roots of a formerly susceptible plant and discover that the roots expressing this artificial construct we made had higher soybean cyst nematode resistance.
Sevie Kenyon: Can you paint us a picture of what this research looks like?
Andrew Bent: We have soybean root segments on petri plates, nematodes that we raise up in greenhouses, pipettes and test tubes for doing DNA manipulation. Microscopes for being able to envision, the nematodes are these microscopic worms, tiny little worms that you can’t see with the naked eye. It’s fairly straightforward; we’re not an expensive laboratory at this university.
Sevie Kenyon: We’ve been visiting with Andrew Bent, Department of Plant Pathology, University of Wisconsin in the College of Agricultural and Life Sciences, Madison, WI and I’m Sevie Kenyon.