Searching For A Path To Greater Grains

IRA FLATOW: For the rest of the hour, delving into a grain you might not know much about, talking about sorghum, unless you’re a farmer. It’s the fifth most important cereal crop in the world. It’s a common human food ingredient in Africa, parts of Asia.

In the US, it’s mainly used for animal feed or for ethanol production with millions of acres of the grain planted in the US every year. But now writing in the journal Nature Communications, researchers report that they’ve identified the pathway in one mutant strain of the grain that allows that variety to produce three times as many seeds per plant as regular sorghum.

Doreen Ware, one of the authors of the report, is a plant molecular biologist with the USDA’s Agricultural Research Service and an adjunct associate professor at Cold Spring Harbor Laboratory. That’s out there in Cold Spring Harbor, Long Island. She joins me by Skype. Welcome to Science Friday.

DOREEN WARE: Thank you, Ira. I’m really excited to be here today.

IRA FLATOW: Yeah. We’re happy to have you. Let’s talk about– this is fascinating. This just jumped out at me, because I’m a plant person, you know? And your study worked on the flowers and seeds of the sorghum plant. It’s kind of a grass, for those listeners who haven’t looked up close at some sorghum lately. But tell us what does it look like.

DOREEN WARE: So it basically looks a lot like corn, if you’ve seen a corn field, but if you look at the top of the plant, that’s where the flowers are in sorghum. and the top part of the plant has many different flowers on it. Hundreds of flowers will be on the top of this panicle. But normally, in nature, when you look at that panicle, only half of the flowers, or less than half of the flowers, are normally fertile and make seed.

But what we were able to find out about was that one of our colleagues in Texas, a USDA breeder, was introducing novel genetic variation into sorghum using traditional approaches that readers have been using for many, many years. And what he found in his field were a few of these plants now where the flowers– almost all of them were fertile in that top panicle.

And this was really, really unusual. We never ever see about all the flowers being fertile. And by increasing the fertility of that plant, we were able to actually increase the number of grains that that would have. And this is really, really critical, because as we’re thinking about needing to grow more food with the same amount of land and less resources to feed 10 billion people by 2050, it’s going to be really important for us to think how we might approach this. And increasing the number of seeds on a single plant might be one of those approaches.

IRA FLATOW: You say might be because you haven’t actually grown all those seeds to see if they might makes plants and produce food.

DOREEN WARE: Well, actually, we’ve been able to grow the plants, but it turns out that in order to grow different varieties of sorghum in local environments, you might have to introduce the variation that we’ve identified and test it out. So what we can do is we can make all those flowers fertile, but we might have to do some additional modifications, for instance to make the seeds a little larger or to have them have more of the nutrients and things in those individual seeds.

I was really excited to hear that the background that you provided on sorghum, because I think most people aren’t familiar with it. And if you think about it, sorghum is a major crop in Africa. And it grew up in Africa. And one of the really wonderful things about sorghum is over its lifetime it’s learned these secrets of how to grow well in hot climates and in really poor soils.

And that’s going to be really, really important for us here in the US, you know, and sorghum– it’s also emerging as one of those super foods. I don’t know if you know this, or if your listeners know this, but it’s gluten free. You can use it to make flour or beer. You can cook it like quinoa or barley. And it has different colors. And the darker black and burgundy varieties have beneficial anti-oxidants very similar to what you get when you eat grapes and cranberries.

IRA FLATOW: Can you bake? Can you make flour out of it, make bread out of it?

DOREEN WARE: Yes, you can. In fact, it’s actually used to make bread and it’s also used actually for frying as well. It actually turns out that the coating you get when you use sorghum flours really gives you more– you retain more of the moisture inside of the meat or the other products than when you, for instance, would use some other flour types.

Also turns out that it’s a really versatile crop, because not only do we eat the grain portion, either us or as an animal feed, but it turns out that the main body of that plant, that, you know, when you see like the cornstalks in the field, all of that actually can be used for renewable energy to make biofuel.

IRA FLATOW: Wow. This is Science Friday from PRI, Public Radio International. Everything you’ve ever wanted to know about sorghum. I mean we don’t talk much about that. Doreen Ware, plant molecular biologist, is my guest. So the mutation in these plants affects a sort of plant reproductive hormone. Is it in other plants too? I mean can we spread the love out here to other plants?

DOREEN WARE: Yeah. No. Actually that’s one of the things that we’re really interested in understanding. So it turns out that the change that we saw was actually in a gene that regulates other genes that make this plant hormone. And you can kind of think about this gene as like a manager. It tells the other genes when to turn on or when to turn off.

And it turns out that plants, like animals, have hormones and, in this case, when we decrease the amount of hormone that’s around, it turns out it makes those flowers fertile now. And when we increase the amount of hormone around, it actually decreases the number of flowers.

And we were able to actually test that hypothesis by taking that new variety and we added external hormone to that plant. And we were able to get it now to make less seeds than what it– less grains on the plant or less fertile flowers than what it was making before. So we understand now this mechanism.

And it turns out that when you look at plants, especially closely related species like the grasses we’re talking about, like wheat, like rice, barley, and corn, that a lot of times those genes are– they’re using the same set of genes. But what they might be doing is changing it up a little bit. Maybe they’ll leave one out, when and where they might turn them on and off might change, and that’s what gives us those different flower architectures. It’s that slight shifting [? and ?] nuances that are happening.

So what we now understand is this underlying mechanism of how the plant may be changing its fertility. And we can see if that also holds true in some of these other grasses. And the approach that we would use is to look to see if those genes exist, and then to see if they’re turned on and off at similar times in the plants. And so those are things that we’re moving forward with right now.

IRA FLATOW: So why would a plant devolve to waste energy on making flowers that don’t produce fruit or conversely, you know?

DOREEN WARE: That’s a really interesting question. And I think if we go back to where did sorghum originate– so sorghum originated in Africa. And it turns out that it basically grew up in very harsh conditions. And as I mentioned earlier, plants will use the same sort of, you would call them gene modules, over and over to make a flower structure.

But it turns out that in sub-sahara Africa, maybe an adaptive response was not to make as many into the seeds, because by making less seeds, you would be able to put, for instance, more resources into the seeds that you have, and perhaps those seeds may be more competitive in that very harsh environment.

That’s just a hypothesis. That’s not that’s not something we know, but you can see how, that for instance what we would call fitness, that maybe sorghum initially did make, or what the ancestor that may have made all the fertile flowers, but it turns out that when it made less, those seeds had a higher fitness level and perhaps the plants overall were more productive that way in the longer term.

So there are different strategies depending upon the adaptive responses. But we’re really interested in understanding of some of the other secrets that sorghum have learned along the way of how to do well under very– with low water usage and very efficient energy conversion.

Whether this has to do with the wax [? depth ?] deposition on the leaves or how it does photosynthesis, these are some of the things that it’s learned to adapt in that climate, and if we can learn more on how it’s done that, then we could maybe apply it to some of these other grasses that we think of more often like rice and wheat, and see if we can actually train them or have them learn a new trick of how to grow better using less water.

IRA FLATOW: Dr. Ware. Thank you. We’ve run out of– this is fascinating. Thank you for sharing your expertise with us on that. Dr. Dareen Ware, the molecular biologist at the USDA’s agricultural research service. And she’s out there in Cold Spring Harbor, Long Island.

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