Transcript

Plant Biotechnology with Roger Parish

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Matt Smith:

This is the La Trobe University podcast. I'd be your host Matt Smith. Good morning, good afternoon and good evening, it does all depend on where you're standing. I'm joined here today by Professor Roger Parish from the Department of Botany. Let's give him a big round of applause. Thanks for being here today Roger.

Roger Parish:

Pleasure.

Matt Smith:

Now you're here to talk to us today about plant biotechnology. Now I'd like to ask you, firstly, why produce hybrid plants?

Roger Parish:

Well the idea is we want to increase yields at a minimum cost and the way we can do this is by crossing the inbred lines of the species and you get yield increases up to 50%. The increase yield is one advantage; the other advantages are increased, improved resistance to diseases, viruses, bacteria, fungi and also to stresses - what we call abiotic stresses, things like heat, drought, cold, and so on.

Matt Smith:

So you said that inbred lines of the species, what is that?

Roger Parish:

Well, most of our crops are inbred in the sense that they're self fertilizing. In other words then the stem, the part which produces the pollen - they're very close to the female part of the flower and the chances that the plant can be fertilized by pollen from another plant or another flower is very, very small. So you have self fertilization over time and that's inbreeding and so we have these inbred lines.

So we take two of those lines and then we cross them. And it's very difficult to cross them just because of the inbreeding situation. And so what we have to do is to prevent the pollen being made in the female plant and the plant is just a female plant so it can't self fertilize itself.

So we need to block pollen production in the plant in one of the plants that we are going to use for the crossing. And the way we do that is to discover the genes that are essential for the production of that particular pollen. And so part of the project was to identify genes that are required for normal pollen production and to knock them out - to inhibit them from being what we call expressed.

But we identified about six or seven genes which looked to be important and we narrowed that down to one particular gene which was excellent, very exceptionally essential for pollen production in the Brassica species we're looking at. They're the cabbage type crops - things like canola and we work with a plant called Ahrhodopsis which is a laboratory plant. We worked with it, but it belongs to the Brassicas.

Now, these are self fertilizing plants so we have to stop the pollen production in this particular plant that we want to be the female and then we can have the pollen from the male coming in and fertilizing and now cross these two inbred lines—pollen from one and the female side from the other that the female not being able to make any pollen.

And the problem with that is if we leave the female as it is the female is crossed with the other pollen. But we want to overcome this male sterility if we're going to have hybrid vigor because that – so you've got a female plant which is male sterile of course and then you cross that with pollen from another plant.

You want to make sure that the seeds that you receive from that give rise to plants which are not male sterile. So you have to reverse the male sterility in the hybrid that you get after the cross. So there are two things that you have to do. You have to find the gene or genes that are important in pollen development and then you have to be able to turn them off, but you have to be able to turn them back on again in the hybrid plant.

Matt Smith:

So is this something that you can actually do? You can turn on a gene in a plant that is already growing?

Roger Parish:

That's right. And we can do that. I'll tell you how we can do that. First of all, we come back to how we turn the genes off. We identified one particular gene which goes for protein which is a protein that we call them master switches or transcription factors, which bind very specifically to one or very few other genes and turn them on or off.

In the case of that particular protein, it seems to turn one or two other genes on, which are absolutely essential for pollen development. So if our protein isn't there those genes can't be turn on and as a result we have a male sterile phenotype. We don't get any viable pollen.

Matt Smith:

So how do you go about turning the gene off?

Roger Parish:

Well, we put in an exact copy of the gene into the plant. We add an extra 5 to 10 or 10 to 12 amino acids. You know, proteins are made of amino acids. So we add in the genetic code which adds these 10 amino acids to the protein.

So we're putting up the gene in a way we've got a protein that's the same protein with just a little tiny, a little bit longer and these 10 amino acids actually turn the protein into a repressor. So, instead of activating genes, it represses them and it competes with the normal protein that's in there, which doesn't have this repressor sequence as we call it and prevents that normal gene and that normal protein from turning on the genes that or genes or genes that it would turn on.

Matt Smith:

Is it an overload?

Roger Parish:

Yes, in a way it is. You've got - Well you put in enough of that repressor that it would compete vigorously with the endogenous as we call it - the normal protein in the plant. But it also because it has these 10 amino acids it prevents the whole activation machinery from functioning. Now how do we turn it on again? What we can do with that is we take the plant that's providing the male pollen, deriving the pollen to this now male sterile or female and we put that particular gene into that plant, the one providing the pollen, and so this pollen now is making quite a lot, a lot more of that protein than it would normally need. The protein – it's critical.

And then, when that pollen fertilizes the male sterile plant, the seeds that result from that fertilization, when they grow, they have extra copies and more of that particular gene so that it can overcome the inhibitory effect that we originally put in. In other words, we're saturating the inhibitory effect with more of the protein.

Matt Smith:

Now, this new hybrid plants that you come up with, do you, therefore, need to turn off their genes to make sure they don't self pollinate or if they self pollinate will they still be the hybrids?

Roger Parish:

It doesn't matter and whether self pollinate or not. We'll still have the hybrid vigour. But one of the problems with hybrid vigour is that it only lasts for few generations. So let's say you get a 30 to 40% increase in productivity in the first generation, it's going to steadily drop off during subsequent generations and come back to the original level.

People don't really understand the genetic level how hybrid vigour works for quite a number – there are a number of theories. But it's not a 100% clear how that really works and why they actually dilute out further on their theories about that as well.

So that means one has to keep producing hybrid seed of the sort for the farmers. There has to be continually new seed made and the farmers have to buy new seed. They can't use their old seed all the time with the yields as high as they are that it shouldn't or it isn't usually a problem.

Matt Smith:

The implications of you developing something like this means you can patent the process, can't you?

Roger Parish:

Yes. Yes. We have patented this process internationally you know in many countries around the world and now we have an industrial collaborator. They're working with us and we've received funding. We have funding from the NRC and consumed about $800,000 for the next 3 or 4 years to continue this project and to expand to other crops, in particular crops like canola.

We've taken canola a long way down the track but we've isolated this gene in a lot of other crops. It's a very common gene right across the plant world. We've isolated the gene from wheat, barley, rice. It's in all the crops we've looked at so far.

And so we can use and we can turn that gene off in any of the crops we're interested in and we're particularly working now with, working together with this company on canola and on a related species, closely related species of canola which is even more drought resistant than canola. It would probably be ideal for Australian conditions. It's very widely grown in India and also on cotton.

Matt Smith:

So you found the gene to stop self pollenisation. You switched it off. Are there any other genes you attempted to muck around within there?

Roger Parish:

We don't need to in this particular case. We are looking at other genes in plants which are of interest to us. Genes that are involved in plant development. Genes that are involved in resistance to, for example cold, encoding proteins that protect plants against cold, protect proteins and plants against drought, and also with some recent work of genes that are essential for the development of seeds, particularly the seed coat, which protects the seed, and also production of mucilage by the seeds which also protects the seeds. And this is very important in seed hydration and germination. So we're understanding the way in which those genes regulate the production of these particular cell types and that of their products.

Matt Smith:

These hybrid crops that you've produced, did they specifically develop to benefit in Australian environment or are they the sort of things that can be extended worldwide?

Roger Parish:

Oh this can be extended worldwide. I mean it depends on what particular variety one uses and the varieties of various crops that we developed to various climates, winter wheat and so on. So really it can work in any plant. It just depends on which variety you take and so it's a worldwide. It's a technology that has application right across other agriculture – across the world.

Matt Smith:

Are there any implications in using this sort of technology that you have to go through if you're changing something strain we've got a genetically-engineered crop.

Roger Parish:

Yes this would be GM crops. There's no doubt about that, it would be registered as a GM crop although the genes we used are all genes from the same plant. It's not that we're putting any foreign genes into the plant or regulating foreign genes. They were genes from the plant. It still qualifies -

Matt Smith:

You're not using frog DNA.

Roger Parish:

We're not using?

Matt Smith:

Frog DNA.

Roger Parish:

No. We're not using frog DNA or fish DNA, or martian DNA or anything like that. It's all from that particular crop but it's still qualified as genetic—GM, genetically modified.

If one prevents crops from being fertilized,without worrying about the crossing, just by preventing the self-fertilization, crops will continue to grow and produce in larger mass, more leaves and so the bio-mass levels go up. This means more feed for animals and it can also, by preventing the plants from making pollen, genetically engineered plants can no longer disperse pollen which you know that could prevent the spread of the foreign genes, if you like, into related crops. Now this is only useful of course if one is interested in the leaves and not in the grain or the seeds.

Matt Smith:

Professor Roger Parish, thank you for your time today.

Roger Parish:

Pleasure.

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