0:00:00.840,0:00:05.056
I believe that the secret to producing[br]extremely drought-tolerant crops,

0:00:05.080,0:00:08.296
which should go some way[br]to providing food security in the world,

0:00:08.320,0:00:11.016
lies in resurrection plants,

0:00:11.040,0:00:14.176
pictured here, in an extremely[br]droughted state.

0:00:14.200,0:00:17.056
You might think[br]that these plants look dead,

0:00:17.080,0:00:18.376
but they're not.

0:00:18.400,0:00:19.856
Give them water,

0:00:19.880,0:00:25.320
and they will resurrect, green up,[br]start growing, in 12 to 48 hours.

0:00:26.320,0:00:27.616
Now, why would I suggest

0:00:27.640,0:00:32.080
that producing drought-tolerant crops[br]will go towards providing food security?

0:00:33.040,0:00:36.936
Well, the current world population[br]is around 7 billion.

0:00:36.960,0:00:39.456
And it's estimated that by 2050,

0:00:39.480,0:00:42.176
we'll be between 9 and 10 billion people,

0:00:42.200,0:00:45.080
with the bulk of this growth[br]happening in Africa.

0:00:45.880,0:00:48.336
The food and agricultural[br]organizations of the world

0:00:48.360,0:00:51.496
have suggested that we need[br]a 70 percent increase

0:00:51.520,0:00:53.696
in current agricultural practice

0:00:53.720,0:00:54.960
to meet that demand.

0:00:55.720,0:00:58.416
Given that plants[br]are at the base of the food chain,

0:00:58.440,0:01:00.760
most of that's going[br]to have to come from plants.

0:01:01.360,0:01:04.056
That percentage of 70 percent

0:01:04.080,0:01:08.296
does not take into consideration[br]the potential effects of climate change.

0:01:08.320,0:01:12.560
This is taken from a study by Dai[br]published in 2011,

0:01:13.240,0:01:15.176
where he took into consideration

0:01:15.200,0:01:17.576
all the potential effects[br]of climate change

0:01:17.600,0:01:19.736
and expressed them --[br]amongst other things --

0:01:19.760,0:01:24.376
increased aridity due to lack of rain[br]or infrequent rain.

0:01:24.400,0:01:26.176
The areas in red shown here,

0:01:26.200,0:01:28.256
are areas that until recently

0:01:28.280,0:01:31.456
have been very successfully[br]used for agriculture,

0:01:31.480,0:01:33.880
but cannot anymore[br]because of lack of rainfall.

0:01:34.640,0:01:37.560
This is the situation[br]that's predicted to happen in 2050.

0:01:38.840,0:01:41.016
Much of Africa,[br]in fact, much of the world,

0:01:41.040,0:01:42.936
is going to be in trouble.

0:01:42.960,0:01:46.616
We're going to have to think of some[br]very smart ways of producing food.

0:01:46.640,0:01:49.936
And preferably among them,[br]some drought-tolerant crops.

0:01:49.960,0:01:52.016
The other thing[br]to remember about Africa is

0:01:52.040,0:01:54.840
that most of their agriculture is rainfed.

0:01:56.080,0:01:59.536
Now, making drought-tolerant crops[br]is not the easiest thing in the world.

0:01:59.560,0:02:01.976
And the reason for this is water.

0:02:02.000,0:02:05.136
Water is essential to life on this planet.

0:02:05.160,0:02:09.295
All living, actively[br]metabolizing organisms,

0:02:09.320,0:02:11.376
from microbes to you and I,

0:02:11.400,0:02:13.736
are comprised predominately of water.

0:02:13.760,0:02:16.296
All life reactions happen in water.

0:02:16.320,0:02:19.336
And loss of a small amount[br]of water results in death.

0:02:19.360,0:02:21.416
You and I are 65 percent water --

0:02:21.440,0:02:23.160
we lose one percent of that, we die.

0:02:23.840,0:02:26.560
But we can make behavioral[br]changes to avoid that.

0:02:27.920,0:02:29.496
Plants can't.

0:02:29.520,0:02:31.136
They're stuck in the ground.

0:02:31.160,0:02:34.536
And so in the first instance they have[br]a little bit more water than us,

0:02:34.560,0:02:35.816
about 95 percent water,

0:02:35.840,0:02:37.936
and they can lose[br]a little bit more than us,

0:02:37.960,0:02:40.920
like 10 to about 70 percent,[br]depending on the species,

0:02:42.000,0:02:43.360
but for short periods only.

0:02:44.680,0:02:48.856
Most of them will either try[br]to resist or avoid water loss.

0:02:48.880,0:02:52.816
So extreme examples of resistors[br]can be found in succulents.

0:02:52.840,0:02:55.656
They tend to be small, very attractive,

0:02:55.680,0:02:58.416
but they hold onto their water[br]at such great cost

0:02:58.440,0:03:00.440
that they grow extremely slowly.

0:03:01.440,0:03:06.016
Examples of avoidance of water loss[br]are found in trees and shrubs.

0:03:06.040,0:03:07.616
They send down very deep roots,

0:03:07.640,0:03:09.336
mine subterranean water supplies

0:03:09.360,0:03:11.816
and just keep flushing[br]it through them at all times,

0:03:11.840,0:03:13.696
keeping themselves hydrated.

0:03:13.720,0:03:15.696
The one on the right is called a baobab.

0:03:15.720,0:03:17.776
It's also called the upside-down tree,

0:03:17.800,0:03:21.576
simply because the proportion[br]of roots to shoots is so great

0:03:21.600,0:03:24.296
that it looks like the tree[br]has been planted upside down.

0:03:24.320,0:03:27.560
And of course the roots are required[br]for hydration of that plant.

0:03:28.760,0:03:33.280
And probably the most common strategy[br]of avoidance is found in annuals.

0:03:33.840,0:03:37.016
Annuals make up the bulk[br]of our plant food supplies.

0:03:37.040,0:03:38.736
Up the west coast of my country,

0:03:38.760,0:03:42.296
for much of the year[br]you don't see much vegetation growth.

0:03:42.320,0:03:44.976
But come the spring rains, you get this:

0:03:45.000,0:03:46.240
flowering of the desert.

0:03:47.000,0:03:48.856
The strategy in annuals,

0:03:48.880,0:03:51.240
is to grow only in the rainy season.

0:03:51.960,0:03:54.256
At the end of that season[br]they produce a seed,

0:03:54.280,0:03:57.096
which is dry, eight to 10 percent water,

0:03:57.120,0:03:58.776
but very much alive.

0:03:58.800,0:04:01.696
And anything that is[br]that dry and still alive,

0:04:01.720,0:04:03.200
we call desiccation-tolerant.

0:04:03.840,0:04:05.256
In the desiccated state,

0:04:05.280,0:04:07.936
what seeds can do[br]is lie in extremes of environment

0:04:07.960,0:04:09.616
for prolonged periods of time.

0:04:09.640,0:04:11.856
The next time the rainy season comes,

0:04:11.880,0:04:13.376
they germinate and grow,

0:04:13.400,0:04:15.280
and the whole cycle just starts again.

0:04:16.120,0:04:20.176
It's widely believed that the evolution[br]of desiccation-tolerant seeds

0:04:20.200,0:04:22.376
allowed the colonization and the radiation

0:04:22.400,0:04:25.920
of flowering plants,[br]or angiosperms, onto land.

0:04:26.960,0:04:30.120
But back to annuals[br]as our major form of food supplies.

0:04:30.800,0:04:35.520
Wheat, rice and maize form 95 percent[br]of our plant food supplies.

0:04:36.480,0:04:38.016
And it's been a great strategy

0:04:38.040,0:04:41.216
because in a short space of time[br]you can produce a lot of seed.

0:04:41.240,0:04:43.860
Seeds are energy-rich[br]so there's a lot of food calories,

0:04:43.884,0:04:47.804
you can store it in times of plenty[br]for times of famine,

0:04:48.480,0:04:49.720
but there's a downside.

0:04:50.560,0:04:51.936
The vegetative tissues,

0:04:51.960,0:04:54.136
the roots and leaves of annuals,

0:04:54.160,0:04:55.416
do not have much

0:04:55.440,0:04:59.536
by way of inherent resistance,[br]avoidance or tolerance characteristics.

0:04:59.560,0:05:00.856
They just don't need them.

0:05:00.880,0:05:02.296
They grow in the rainy season

0:05:02.320,0:05:05.696
and they've got a seed[br]to help them survive the rest of the year.

0:05:05.720,0:05:08.416
And so despite concerted[br]efforts in agriculture

0:05:08.440,0:05:10.976
to make crops with improved properties

0:05:11.000,0:05:13.176
of resistance, avoidance and tolerance --

0:05:13.200,0:05:15.096
particularly resistance and avoidance

0:05:15.120,0:05:18.016
because we've had good models[br]to understand how those work --

0:05:18.040,0:05:20.376
we still get images like this.

0:05:20.400,0:05:21.856
Maize crop in Africa,

0:05:21.880,0:05:23.296
two weeks without rain

0:05:23.320,0:05:24.520
and it's dead.

0:05:25.560,0:05:26.800
There is a solution:

0:05:27.520,0:05:28.760
resurrection plants.

0:05:29.320,0:05:33.096
These plants can lose 95 percent[br]of their cellular water,

0:05:33.120,0:05:36.976
remain in a dry, dead-like state[br]for months to years,

0:05:37.000,0:05:38.736
and give them water,

0:05:38.760,0:05:40.640
they green up and start growing again.

0:05:41.560,0:05:44.856
Like seeds, these are[br]desiccation-tolerant.

0:05:44.880,0:05:49.000
Like seeds, these can withstand extremes[br]of environmental conditions.

0:05:49.760,0:05:51.776
And this is a really rare phenomenon.

0:05:51.800,0:05:56.176
There are only 135 flowering[br]plant species that can do this.

0:05:56.200,0:05:57.616
I'm going to show you a video

0:05:57.640,0:06:00.256
of the resurrection process[br]of these three species

0:06:00.280,0:06:01.496
in that order.

0:06:01.520,0:06:02.776
And at the bottom,

0:06:02.800,0:06:05.536
there's a time axis[br]so you can see how quickly it happens.

0:06:44.160,0:06:46.200
(Applause)

0:06:50.240,0:06:51.776
Pretty amazing, huh?

0:06:51.800,0:06:56.016
So I've spent the last 21 years[br]trying to understand how they do this.

0:06:56.040,0:06:58.440
How do these plants dry without dying?

0:06:59.080,0:07:01.856
And I work on a variety[br]of different resurrection plants,

0:07:01.880,0:07:04.296
shown here in the hydrated and dry states,

0:07:04.320,0:07:05.776
for a number of reasons.

0:07:05.800,0:07:08.656
One of them is that each[br]of these plants serves as a model

0:07:08.680,0:07:11.056
for a crop that I'd like[br]to make drought-tolerant.

0:07:11.080,0:07:14.016
So on the extreme top left,[br]for example, is a grass,

0:07:14.040,0:07:16.296
it's called Eragrostis nindensis,

0:07:16.320,0:07:18.696
it's got a close relative[br]called Eragrostis tef --

0:07:18.720,0:07:20.736
a lot of you might know it as "teff" --

0:07:20.760,0:07:22.496
it's a staple food in Ethiopia,

0:07:22.520,0:07:23.776
it's gluten-free,

0:07:23.800,0:07:26.816
and it's something we would like[br]to make drought-tolerant.

0:07:26.840,0:07:29.256
The other reason for looking[br]at a number of plants,

0:07:29.280,0:07:30.656
is that, at least initially,

0:07:30.680,0:07:32.936
I wanted to find out:[br]do they do the same thing?

0:07:32.960,0:07:34.656
Do they all use the same mechanisms

0:07:34.680,0:07:37.256
to be able to lose[br]all that water and not die?

0:07:37.280,0:07:39.976
So I undertook what we call[br]a systems biology approach

0:07:40.000,0:07:42.176
in order to get[br]a comprehensive understanding

0:07:42.200,0:07:44.216
of desiccation tolerance,

0:07:44.240,0:07:45.696
in which we look at everything

0:07:45.720,0:07:48.632
from the molecular to the whole plant,[br]ecophysiological level.

0:07:48.657,0:07:50.291
For example we look at things like

0:07:50.316,0:07:52.513
changes in the plant anatomy[br]as they dried out

0:07:52.537,0:07:53.776
and their ultrastructure.

0:07:53.800,0:07:56.976
We look at the transcriptome,[br]which is just a term for a technology

0:07:57.000,0:07:58.416
in which we look at the genes

0:07:58.440,0:08:00.856
that are switched on or off,[br]in response to drying.

0:08:00.880,0:08:04.096
Most genes will code for proteins,[br]so we look at the proteome.

0:08:04.120,0:08:06.520
What are the proteins made[br]in response to drying?

0:08:07.480,0:08:11.376
Some proteins would code for enzymes[br]which make metabolites,

0:08:11.400,0:08:12.976
so we look at the metabolome.

0:08:13.000,0:08:16.296
Now, this is important[br]because plants are stuck in the ground.

0:08:16.320,0:08:20.416
They use what I call[br]a highly tuned chemical arsenal

0:08:20.440,0:08:23.856
to protect themselves from all[br]the stresses of their environment.

0:08:23.880,0:08:25.376
So it's important that we look

0:08:25.400,0:08:27.840
at the chemical changes[br]involved in drying.

0:08:28.520,0:08:31.176
And at the last study[br]that we do at the molecular level,

0:08:31.200,0:08:32.456
we look at the lipidome --

0:08:32.480,0:08:34.535
the lipid changes in response to drying.

0:08:34.559,0:08:35.816
And that's also important

0:08:35.840,0:08:38.655
because all biological membranes[br]are made of lipids.

0:08:38.679,0:08:41.256
They're held as membranes[br]because they're in water.

0:08:41.280,0:08:43.520
Take away the water,[br]those membranes fall apart.

0:08:44.240,0:08:47.280
Lipids also act as signals[br]to turn on genes.

0:08:48.200,0:08:50.896
Then we use physiological[br]and biochemical studies

0:08:50.920,0:08:54.136
to try and understand[br]the function of the putative protectants

0:08:54.160,0:08:57.096
that we've actually discovered[br]in our other studies.

0:08:57.120,0:08:59.296
And then use all of that[br]to try and understand

0:08:59.320,0:09:01.640
how the plant copes[br]with its natural environment.

0:09:03.480,0:09:07.816
I've always had the philosophy that[br]I needed a comprehensive understanding

0:09:07.840,0:09:10.096
of the mechanisms of desiccation tolerance

0:09:10.120,0:09:13.960
in order to make a meaningful suggestion[br]for a biotic application.

0:09:15.000,0:09:16.656
I'm sure some of you are thinking,

0:09:16.680,0:09:17.936
"By biotic application,

0:09:17.960,0:09:20.880
does she mean she's going to make[br]genetically modified crops?"

0:09:22.240,0:09:23.936
And the answer to that question is:

0:09:23.960,0:09:26.341
depends on your definition[br]of genetic modification.

0:09:27.200,0:09:30.016
All of the crops that we eat today,[br]wheat, rice and maize,

0:09:30.040,0:09:33.256
are highly genetically modified[br]from their ancestors,

0:09:33.280,0:09:35.256
but we don't consider them GM

0:09:35.280,0:09:37.920
because they're being produced[br]by conventional breeding.

0:09:38.880,0:09:42.656
If you mean, am I going to put[br]resurrection plant genes into crops,

0:09:42.680,0:09:43.976
your answer is yes.

0:09:44.000,0:09:47.136
In the essence of time,[br]we have tried that approach.

0:09:47.160,0:09:50.016
More appropriately,[br]some of my collaborators at UCT,

0:09:50.040,0:09:51.976
Jennifer Thomson, Suhail Rafudeen,

0:09:52.000,0:09:53.616
have spearheaded that approach

0:09:53.640,0:09:55.593
and I'm going to show you some data soon.

0:09:57.200,0:10:01.216
But we're about to embark[br]upon an extremely ambitious approach,

0:10:01.240,0:10:04.696
in which we aim to turn on[br]whole suites of genes

0:10:04.720,0:10:07.416
that are already present in every crop.

0:10:07.440,0:10:10.345
They're just never turned on[br]under extreme drought conditions.

0:10:10.800,0:10:12.256
I leave it up to you to decide

0:10:12.280,0:10:14.233
whether those should be called GM or not.

0:10:15.560,0:10:19.016
I'm going to now just give you[br]some of the data from that first approach.

0:10:19.040,0:10:20.296
And in order to do that

0:10:20.320,0:10:22.976
I have to explain a little bit[br]about how genes work.

0:10:23.000,0:10:24.256
So you probably all know

0:10:24.280,0:10:26.336
that genes are made[br]of double-stranded DNA.

0:10:26.360,0:10:28.296
It's wound very tightly into chromosomes

0:10:28.320,0:10:31.480
that are present in every cell[br]of your body or in a plant's body.

0:10:32.080,0:10:35.160
If you unwind that DNA, you get genes.

0:10:35.840,0:10:38.296
And each gene has a promoter,

0:10:38.320,0:10:40.696
which is just an on-off switch,

0:10:40.720,0:10:42.136
the gene coding region,

0:10:42.160,0:10:43.416
and then a terminator,

0:10:43.440,0:10:47.040
which indicates that this is the end[br]of this gene, the next gene will start.

0:10:47.720,0:10:50.616
Now, promoters are not[br]simple on-off switches.

0:10:50.640,0:10:53.336
They normally require[br]a lot of fine-tuning,

0:10:53.360,0:10:57.400
lots of things to be present and correct[br]before that gene is switched on.

0:10:58.240,0:11:01.296
So what's typically done[br]in biotech studies

0:11:01.320,0:11:03.136
is that we use an inducible promoter,

0:11:03.160,0:11:04.736
we know how to switch it on.

0:11:04.760,0:11:06.776
We couple that to genes of interest

0:11:06.800,0:11:09.480
and put that into a plant[br]and see how the plant responds.

0:11:10.120,0:11:12.696
In the study that I'm going[br]to talk to you about,

0:11:12.720,0:11:15.176
my collaborators used[br]a drought-induced promoter,

0:11:15.200,0:11:17.616
which we discovered[br]in a resurrection plant.

0:11:17.640,0:11:20.776
The nice thing about this promoter[br]is that we do nothing.

0:11:20.800,0:11:22.880
The plant itself senses drought.

0:11:23.600,0:11:28.696
And we've used it to drive antioxidant[br]genes from resurrection plants.

0:11:28.720,0:11:30.576
Why antioxidant genes?

0:11:30.600,0:11:33.656
Well, all stresses,[br]particularly drought stress,

0:11:33.680,0:11:35.976
results in the formation of free radicals,

0:11:36.000,0:11:38.336
or reactive oxygen species,

0:11:38.360,0:11:41.080
which are highly damaging[br]and can cause crop death.

0:11:41.680,0:11:44.280
What antioxidants do is stop that damage.

0:11:45.360,0:11:49.256
So here's some data from a maize strain[br]that's very popularly used in Africa.

0:11:49.280,0:11:52.576
To the left of the arrow[br]are plants without the genes,

0:11:52.600,0:11:53.856
to the right --

0:11:53.880,0:11:55.936
plants with the antioxidant genes.

0:11:55.960,0:11:57.776
After three weeks without watering,

0:11:57.800,0:12:00.280
the ones with the genes[br]do a hell of a lot better.

0:12:01.720,0:12:03.056
Now to the final approach.

0:12:03.080,0:12:06.616
My research has shown[br]that there's considerable similarity

0:12:06.640,0:12:11.056
in the mechanisms of desiccation tolerance[br]in seeds and resurrection plants.

0:12:11.080,0:12:12.496
So I ask the question,

0:12:12.520,0:12:13.960
are they using the same genes?

0:12:14.480,0:12:16.736
Or slightly differently phrased,

0:12:16.760,0:12:21.256
are resurrection plants using genes[br]evolved in seed desiccation tolerance

0:12:21.280,0:12:22.536
in their roots and leaves?

0:12:22.560,0:12:24.616
Have they retasked these seed genes

0:12:24.640,0:12:26.680
in roots and leaves[br]of resurrection plants?

0:12:27.760,0:12:29.616
And I answer that question,

0:12:29.640,0:12:32.056
as a consequence of a lot[br]of research from my group

0:12:32.080,0:12:35.616
and recent collaborations from a group[br]of Henk Hilhorst in the Netherlands,

0:12:35.640,0:12:37.216
Mel Oliver in the United States

0:12:37.240,0:12:39.840
and Julia Buitink in France.

0:12:39.880,0:12:41.296
The answer is yes,

0:12:41.320,0:12:44.176
that there is a core set of genes[br]that are involved in both.

0:12:44.200,0:12:47.616
And I'm going to illustrate this[br]very crudely for maize,

0:12:47.640,0:12:50.056
where the chromosomes below the off switch

0:12:50.080,0:12:53.655
represent all the genes that are required[br]for desiccation tolerance.

0:12:53.680,0:12:57.936
So as maize seeds dried out[br]at the end of their period of development,

0:12:57.960,0:12:59.320
they switch these genes on.

0:13:00.680,0:13:03.576
Resurrection plants[br]switch on the same genes

0:13:03.600,0:13:05.256
when they dry out.

0:13:05.280,0:13:07.056
All modern crops, therefore,

0:13:07.080,0:13:09.136
have these genes[br]in their roots and leaves,

0:13:09.160,0:13:10.896
they just never switch them on.

0:13:10.920,0:13:12.880
They only switch them on in seed tissues.

0:13:13.440,0:13:15.176
So what we're trying to do right now

0:13:15.200,0:13:17.816
is to understand the environmental[br]and cellular signals

0:13:17.840,0:13:20.280
that switch on these genes[br]in resurrection plants,

0:13:21.280,0:13:23.040
to mimic the process in crops.

0:13:23.680,0:13:25.416
And just a final thought.

0:13:25.440,0:13:27.656
What we're trying to do very rapidly

0:13:27.680,0:13:31.496
is to repeat what nature did[br]in the evolution of resurrection plants

0:13:31.520,0:13:33.360
some 10 to 40 million years ago.

0:13:34.160,0:13:36.656
My plants and I thank you[br]for your attention.

0:13:36.680,0:13:42.915
(Applause)