WEBVTT

00:00:00.840 --> 00:00:05.056
I believe that the secret to producing
extremely drought-tolerant crops,

00:00:05.080 --> 00:00:08.296
which should go some way
to providing food security in the world,

00:00:08.320 --> 00:00:11.016
lies in resurrection plants,

00:00:11.040 --> 00:00:14.176
pictured here, in an extremely
droughted state.

00:00:14.200 --> 00:00:17.056
Now, you might think
that these plants look dead,

00:00:17.080 --> 00:00:18.376
but they're not.

00:00:18.400 --> 00:00:19.856
Give them water,

00:00:19.880 --> 00:00:25.320
and they will resurrect, green up,
start growing, in 12 to 48 hours.

00:00:26.320 --> 00:00:27.616
Now, why would I suggest

00:00:27.640 --> 00:00:32.080
that producing drought-tolerant crops
will go towards providing food security?

00:00:33.040 --> 00:00:36.936
Well, the current world population
is around 7 billion.

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

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

00:00:42.200 --> 00:00:45.080
with the bulk of this growth
happening in Africa.

00:00:45.880 --> 00:00:48.336
The food and agricultural
organizations of the world

00:00:48.360 --> 00:00:51.496
have suggested that we need
a 70 percent increase

00:00:51.520 --> 00:00:53.696
in current agricultural practice

00:00:53.720 --> 00:00:54.960
to meet that demand.

00:00:55.720 --> 00:00:58.416
Now, given that plants
are at the base of the food chain,

00:00:58.440 --> 00:01:00.760
most of that's going
to have to come from plants.

00:01:01.360 --> 00:01:04.056
Now, that percentage of 70 percent

00:01:04.080 --> 00:01:08.296
does not take into consideration
the potential effects of climate change.

00:01:08.320 --> 00:01:12.560
This is taken from a study by Dye
published in 2011,

00:01:13.240 --> 00:01:15.176
where he took into consideration

00:01:15.200 --> 00:01:17.576
all the potential effects
of climate change

00:01:17.600 --> 00:01:19.736
and expressed them --
amongst other things --

00:01:19.760 --> 00:01:24.376
increased aridity due to lack of rain
or infrequent rain.

00:01:24.400 --> 00:01:26.176
Now, the areas in red shown here,

00:01:26.200 --> 00:01:28.256
are areas that until recently

00:01:28.280 --> 00:01:31.456
have been very successfully
used for agriculture,

00:01:31.480 --> 00:01:33.880
but cannot anymore
because of lack of rainfall.

00:01:34.640 --> 00:01:37.560
This is the situation
that's predicted to happen in 2050.

00:01:38.840 --> 00:01:41.016
Much of Africa,
in fact, much of the world,

00:01:41.040 --> 00:01:42.936
is going to be in trouble.

00:01:42.960 --> 00:01:46.616
We're going to have to think of some
very smart ways of producing food.

00:01:46.640 --> 00:01:49.936
And preferably among them,
some drought-tolerant crops.

00:01:49.960 --> 00:01:52.016
The other thing
to remember about Africa is

00:01:52.040 --> 00:01:54.840
that most of the agriculture is rainfed.

00:01:56.080 --> 00:01:59.536
Now, making drought-tolerant crops
is not the easiest thing in the world.

00:01:59.560 --> 00:02:01.976
And the reason for this is water.

00:02:02.000 --> 00:02:05.136
Water is essential to life on this planet.

00:02:05.160 --> 00:02:09.295
All living, actively
metabolizing organisms,

00:02:09.320 --> 00:02:11.376
from microbes to you and I,

00:02:11.400 --> 00:02:13.736
are comprised predominately of water,

00:02:13.760 --> 00:02:16.296
all life reactions happen in water,

00:02:16.320 --> 00:02:19.336
and loss of a small amount
of water results in death.

00:02:19.360 --> 00:02:21.416
You and I are 65 percent water,

00:02:21.440 --> 00:02:23.160
we lose one percent of that, we die.

00:02:23.840 --> 00:02:26.560
But we can make behavioral
changes to avoid that.

00:02:27.920 --> 00:02:29.496
Plants can't.

00:02:29.520 --> 00:02:31.136
They're stuck in the ground.

00:02:31.160 --> 00:02:34.536
And so in the first instance they have
a little bit more water than us,

00:02:34.560 --> 00:02:35.816
about 95 percent water,

00:02:35.840 --> 00:02:37.936
and they can lose
a little bit more than us,

00:02:37.960 --> 00:02:40.920
like 10 to about 70 percent,
depending on the species,

00:02:42.000 --> 00:02:43.360
but for short periods only.

00:02:44.680 --> 00:02:48.856
Most of them will either try
to resist or avoid water loss.

00:02:48.880 --> 00:02:52.816
So extreme examples of resistors
can be found in succulents,

00:02:52.840 --> 00:02:55.656
they tend to be small, very attractive,

00:02:55.680 --> 00:02:58.416
but they hold onto their water
at such great cost

00:02:58.440 --> 00:03:00.440
that they grow extremely slowly.

00:03:01.440 --> 00:03:06.016
Examples of avoidance of water loss
are found in trees and shrubs.

00:03:06.040 --> 00:03:07.616
They send down very deep roots,

00:03:07.640 --> 00:03:09.336
mine subterranean water supplies,

00:03:09.360 --> 00:03:11.816
and just keep flushing
it through them at all times,

00:03:11.840 --> 00:03:13.696
keeping themselves hydrated.

00:03:13.720 --> 00:03:15.696
The one on the right is called a baobab,

00:03:15.720 --> 00:03:17.776
it's also called the upside-down tree,

00:03:17.800 --> 00:03:21.576
simply because the proportion
of roots to shoots is so great

00:03:21.600 --> 00:03:24.296
that it looks like the tree
has been planted upside down.

00:03:24.320 --> 00:03:27.560
And of course the roots are required
for hydration of that plant.

00:03:28.760 --> 00:03:33.280
And probably the most common strategy
of avoidance is found in annuals.

00:03:33.840 --> 00:03:37.016
Annuals make up the bulk
of our plant food supplies.

00:03:37.040 --> 00:03:38.736
Up the west coast of my country,

00:03:38.760 --> 00:03:42.296
for much of the year
you don't see much vegetation growth.

00:03:42.320 --> 00:03:44.976
But come the spring rains, you get this.

00:03:45.000 --> 00:03:46.240
Flowering of the desert.

00:03:47.000 --> 00:03:48.856
Now, the strategy in annuals,

00:03:48.880 --> 00:03:51.240
is to grow only in the rainy season.

00:03:51.960 --> 00:03:54.256
At the end of that season
they produce a seed,

00:03:54.280 --> 00:03:57.096
which is dry, eight to 10 percent water,

00:03:57.120 --> 00:03:58.776
but very much alive.

00:03:58.800 --> 00:04:01.696
And anything that is
that dry and still alive,

00:04:01.720 --> 00:04:03.200
we call desiccation-tolerant.

00:04:03.840 --> 00:04:05.256
Now, in the desiccated state,

00:04:05.280 --> 00:04:07.936
what seeds can do
is lie in extremes of environment

00:04:07.960 --> 00:04:09.616
for prolonged periods of time.

00:04:09.640 --> 00:04:11.856
The next time the rainy season comes,

00:04:11.880 --> 00:04:13.376
they germinate and grow,

00:04:13.400 --> 00:04:15.280
and the whole cycle just starts again.

00:04:16.120 --> 00:04:20.176
It's widely believed that the evolution
of desiccation-tolerant seeds

00:04:20.200 --> 00:04:22.376
allowed the colonization and the radiation

00:04:22.400 --> 00:04:25.920
of flowering plants,
or angiosperms, onto land.

00:04:26.960 --> 00:04:30.120
But back to annuals
as our major form of food supplies.

00:04:30.800 --> 00:04:35.520
Wheat, rice and maize form 95 percent
of our plant food supplies.

00:04:36.480 --> 00:04:38.016
And it's been a great strategy

00:04:38.040 --> 00:04:41.216
because in a short space of time
you can produce a lot of seed.

00:04:41.240 --> 00:04:43.860
Seeds are energy-rich
so there's a lot of food calories,

00:04:43.884 --> 00:04:47.804
you can store it in times of plenty
for times of famine,

00:04:48.480 --> 00:04:49.720
but there's a downside.

00:04:50.560 --> 00:04:51.936
The vegetative tissues --

00:04:51.960 --> 00:04:54.136
the roots and leaves of annuals --

00:04:54.160 --> 00:04:55.416
do not have much

00:04:55.440 --> 00:04:59.536
by way of inherent resistance,
avoidance or tolerance characteristics.

00:04:59.560 --> 00:05:00.856
They just don't need them.

00:05:00.880 --> 00:05:02.296
They grow in the rainy season

00:05:02.320 --> 00:05:05.696
and they've got a seed
to help them survive the rest of the year.

00:05:05.720 --> 00:05:08.416
And so despite concerted
efforts in agriculture

00:05:08.440 --> 00:05:10.976
to make crops with improved properties

00:05:11.000 --> 00:05:13.176
of resistance, avoidance and tolerance --

00:05:13.200 --> 00:05:15.096
particularly resistance and avoidance

00:05:15.120 --> 00:05:18.016
because we've had good models
to understand how those work --

00:05:18.040 --> 00:05:20.376
we still get images like this.

00:05:20.400 --> 00:05:21.856
Maize crop in Africa,

00:05:21.880 --> 00:05:23.296
two weeks without rain,

00:05:23.320 --> 00:05:24.520
and it's dead.

00:05:25.560 --> 00:05:26.800
Now there is a solution.

00:05:27.520 --> 00:05:28.760
Resurrection plants.

00:05:29.320 --> 00:05:33.096
These plants can lose 95 percent
of their cellular water,

00:05:33.120 --> 00:05:36.976
remain in a dry, dead-like state
for months to years,

00:05:37.000 --> 00:05:38.736
and give them water,

00:05:38.760 --> 00:05:40.640
they green up and start growing again.

00:05:41.560 --> 00:05:44.856
Like seeds, these are
desiccation-tolerant.

00:05:44.880 --> 00:05:49.000
Like seeds, these can withstand extremes
of environmental conditions.

00:05:49.760 --> 00:05:51.776
And this is a really rare phenomenon.

00:05:51.800 --> 00:05:56.176
There are only 135 flowering
plant species that can do this.

00:05:56.200 --> 00:05:57.616
I'm going to show you a video

00:05:57.640 --> 00:06:00.256
of the resurrection process
of these three species

00:06:00.280 --> 00:06:01.496
in that order.

00:06:01.520 --> 00:06:02.776
And at the bottom,

00:06:02.800 --> 00:06:05.536
there's a time axis
so you can see how quickly it happens.

00:06:05.560 --> 00:06:06.760
[Video]

00:06:44.160 --> 00:06:46.200
(Applause)

00:06:50.240 --> 00:06:51.776
Pretty amazing, huh?

00:06:51.800 --> 00:06:56.016
So I've spent the last 21 years
trying to understand how they do this.

00:06:56.040 --> 00:06:58.440
How do these plants dry without dying?

00:06:59.080 --> 00:07:01.856
And I work on a variety
of different resurrection plants,

00:07:01.880 --> 00:07:04.296
shown here in the hydrated and dry states,

00:07:04.320 --> 00:07:05.776
for a number of reasons.

00:07:05.800 --> 00:07:08.656
One of them is that each
of these plants serves as a model

00:07:08.680 --> 00:07:11.056
for a crop that I'd like
to make drought-tolerant.

00:07:11.080 --> 00:07:14.016
So on the extreme top left,
for example, is a grass,

00:07:14.040 --> 00:07:16.296
it's called Eragrostis nindensis,

00:07:16.320 --> 00:07:18.696
it's got a close relative
called Eragrostis tef --

00:07:18.720 --> 00:07:20.736
a lot of you might know it as "teff" --

00:07:20.760 --> 00:07:22.496
it's a staple food in Ethiopia,

00:07:22.520 --> 00:07:23.776
it's gluten-free,

00:07:23.800 --> 00:07:26.816
and it's something we would like
to make drought-tolerant.

00:07:26.840 --> 00:07:29.256
The other reason for looking
at a number of plants,

00:07:29.280 --> 00:07:30.656
is that, as least initially,

00:07:30.680 --> 00:07:32.936
I wanted to find out:
do they do the same thing?

00:07:32.960 --> 00:07:34.656
Do they all use the same mechanisms

00:07:34.680 --> 00:07:37.256
to be able to lose
all that water and not die?

00:07:37.280 --> 00:07:39.976
So I undertook what we call
a systems biology approach

00:07:40.000 --> 00:07:42.176
in order to get
a comprehensive understanding

00:07:42.200 --> 00:07:44.216
of desiccation tolerance,

00:07:44.240 --> 00:07:45.696
in which we look at everything

00:07:45.720 --> 00:07:48.632
from the molecular to the whole plant,
ecophysiological level.

00:07:48.657 --> 00:07:50.291
For example we look at things like

00:07:50.316 --> 00:07:52.513
changes in the plant anatomy
as they dried out,

00:07:52.537 --> 00:07:53.776
and their ultrastructure.

00:07:53.800 --> 00:07:56.976
We look at the transcriptome,
which is just a term for a technology

00:07:57.000 --> 00:07:58.416
in which we look at the genes

00:07:58.440 --> 00:08:00.856
that are switched on or off,
in response to drying.

00:08:00.880 --> 00:08:04.096
Most genes will code for proteins
so we look at the proteome.

00:08:04.120 --> 00:08:06.520
What are the proteins made
in response to drying?

00:08:07.480 --> 00:08:11.376
Some proteins would code for enzymes
which make metabolites,

00:08:11.400 --> 00:08:12.976
so we look at the metabolome.

00:08:13.000 --> 00:08:16.296
Now, this is important
because plants are stuck in the ground.

00:08:16.320 --> 00:08:20.416
They use what I call
a highly tuned chemical arsenal

00:08:20.440 --> 00:08:23.856
to protect themselves from all
the stresses of their environment.

00:08:23.880 --> 00:08:25.376
So it's important that we look

00:08:25.400 --> 00:08:27.840
at the chemical changes
involved in drying.

00:08:28.520 --> 00:08:31.176
And at the last study
that we do at the molecular level,

00:08:31.200 --> 00:08:32.456
we look at the lipidome --

00:08:32.480 --> 00:08:34.535
the lipid changes in response to drying.

00:08:34.559 --> 00:08:35.816
And that's also important

00:08:35.840 --> 00:08:38.655
because all biological membranes
are made of lipids.

00:08:38.679 --> 00:08:41.256
They're held as membranes
because they're in water.

00:08:41.280 --> 00:08:43.520
Take away the water,
those membranes fall apart.

00:08:44.240 --> 00:08:47.280
Lipids also act as signals
to turn on genes.

00:08:48.200 --> 00:08:50.896
Then we use physiological
and biochemical studies

00:08:50.920 --> 00:08:54.136
to try and understand
the function of the putative protectants

00:08:54.160 --> 00:08:57.096
that we've actually discovered
in our other studies.

00:08:57.120 --> 00:08:59.296
And then use all of that
to try and understand

00:08:59.320 --> 00:09:01.640
how the plant copes
with its natural environment.

00:09:03.480 --> 00:09:07.816
Now, I've always had the philosophy that
I needed a comprehensive understanding

00:09:07.840 --> 00:09:10.096
of the mechanisms of desiccation tolerance

00:09:10.120 --> 00:09:13.960
in order to make a meaningful suggestion
for a biotic application.

00:09:15.000 --> 00:09:16.656
I'm sure some of you are thinking,

00:09:16.680 --> 00:09:17.936
"by biotic application,

00:09:17.960 --> 00:09:20.880
does she mean she's going to make
genetically modified crops?"

00:09:22.240 --> 00:09:23.936
And the answer to that question is:

00:09:23.960 --> 00:09:26.341
depends on your definition
of genetic modification.

00:09:27.200 --> 00:09:30.016
All of the crops that we eat today,
wheat, grass and maize,

00:09:30.040 --> 00:09:33.256
are highly genetically modified
from their ancestors,

00:09:33.280 --> 00:09:35.256
but we don't consider them GM,

00:09:35.280 --> 00:09:37.920
because they're being produced
by conventional breeding.

00:09:38.880 --> 00:09:42.656
If you mean, am I going to put
resurrection plant genes into crops,

00:09:42.680 --> 00:09:43.976
your answer is yes.

00:09:44.000 --> 00:09:47.136
In the essence of time,
we have tried that approach.

00:09:47.160 --> 00:09:50.016
More appropriately,
some of my collaborators at UCT,

00:09:50.040 --> 00:09:51.976
Jennifer Thomson, Suhail Rafudeen,

00:09:52.000 --> 00:09:53.616
have spearheaded that approach

00:09:53.640 --> 00:09:55.593
and I'm going to show you some data soon.

00:09:57.200 --> 00:10:01.216
But we're about to embark
upon an extremely ambitious approach,

00:10:01.240 --> 00:10:04.696
in which we aim to turn on
whole suites of genes

00:10:04.720 --> 00:10:07.416
that are already present in every crop.

00:10:07.440 --> 00:10:10.345
They're just never turned on
under extreme drought conditions.

00:10:10.800 --> 00:10:12.256
I leave it up to you to decide

00:10:12.280 --> 00:10:14.233
whether those should be called GM or not.

00:10:15.560 --> 00:10:19.016
I'm going to now just give you
some of the data from that first approach.

00:10:19.040 --> 00:10:20.296
And in order to do that

00:10:20.320 --> 00:10:22.976
I have to explain a little bit
about how genes work.

00:10:23.000 --> 00:10:24.256
So you probably all know

00:10:24.280 --> 00:10:26.336
that genes are made
of double-stranded DNA.

00:10:26.360 --> 00:10:28.296
It's wound very tightly into chromosomes

00:10:28.320 --> 00:10:31.480
that are present in every cell
of your body or in a plant's body.

00:10:32.080 --> 00:10:35.160
If you unwind that DNA, you get genes.

00:10:35.840 --> 00:10:38.296
And each gene has a promoter,

00:10:38.320 --> 00:10:40.696
which is just an on-off switch,

00:10:40.720 --> 00:10:42.136
the gene coding region,

00:10:42.160 --> 00:10:43.416
and then a terminator,

00:10:43.440 --> 00:10:47.040
which indicates that this is the end
of this gene, the next gene will start.

00:10:47.720 --> 00:10:50.616
Now, promoters are not
simple on-off switches.

00:10:50.640 --> 00:10:53.336
They normally require
a lot of fine-tuning,

00:10:53.360 --> 00:10:57.400
lots of things to be present and correct
before that gene is switched on.

00:10:58.240 --> 00:11:01.296
So what's typically done
in biotech studies

00:11:01.320 --> 00:11:03.136
is that we use an inducible promoter,

00:11:03.160 --> 00:11:04.736
we know how to switch it on.

00:11:04.760 --> 00:11:06.776
We couple that to genes of interest,

00:11:06.800 --> 00:11:09.480
and put that into a plant
and see how the plant responds.

00:11:10.120 --> 00:11:12.696
Now, in the study that I'm going
to talk to you about,

00:11:12.720 --> 00:11:15.176
my collaborators used
a drought-induced promoter,

00:11:15.200 --> 00:11:17.616
which we discovered
in a resurrection plant.

00:11:17.640 --> 00:11:20.776
Now, the nice thing about this promoter
is that we do nothing.

00:11:20.800 --> 00:11:22.880
The plant itself senses drought.

00:11:23.600 --> 00:11:28.696
And we've used it to drive antioxidant
genes from resurrection plants.

00:11:28.720 --> 00:11:30.576
Why antioxidant genes?

00:11:30.600 --> 00:11:33.656
Well, all stresses,
particularly drought stress,

00:11:33.680 --> 00:11:35.976
results in the formation of free radicals,

00:11:36.000 --> 00:11:38.336
or reactive oxygen species,

00:11:38.360 --> 00:11:41.080
which are highly damaging
and can cause crop death.

00:11:41.680 --> 00:11:44.280
What antioxidants do is stop that damage.

00:11:45.360 --> 00:11:49.256
So here's some data from a main strain
that's very popularly used in Africa.

00:11:49.280 --> 00:11:52.576
To the left of the arrow
are plants without the genes,

00:11:52.600 --> 00:11:53.856
to the right --

00:11:53.880 --> 00:11:55.936
plants with the antioxidant genes.

00:11:55.960 --> 00:11:57.776
After three weeks without watering,

00:11:57.800 --> 00:12:00.280
the ones with the genes
do a hell of a lot better.

00:12:01.720 --> 00:12:03.056
Now, to the final approach.

00:12:03.080 --> 00:12:06.616
My research has shown
that there's considerable similarity

00:12:06.640 --> 00:12:11.056
in the mechanisms of desiccation tolerance
in seeds and resurrection plants.

00:12:11.080 --> 00:12:12.496
So I ask the question,

00:12:12.520 --> 00:12:13.960
are they using the same genes?

00:12:14.480 --> 00:12:16.736
Or slightly differently phrased,

00:12:16.760 --> 00:12:21.256
are resurrection plants using genes
evolved in seed desiccation tolerance

00:12:21.280 --> 00:12:22.536
in their roots and leaves?

00:12:22.560 --> 00:12:24.616
Have they retasked these seed genes

00:12:24.640 --> 00:12:26.680
in roots and leaves
of resurrection plants?

00:12:27.760 --> 00:12:29.616
And I answer that question,

00:12:29.640 --> 00:12:32.056
as a consequence of a lot
of research from my group

00:12:32.080 --> 00:12:35.616
and recent collaborations from a group
of Henk Hilhorst in the Netherlands,

00:12:35.640 --> 00:12:37.216
Mel Oliver in the United States,

00:12:37.240 --> 00:12:39.840
and Julia Buitink, in France.

00:12:39.880 --> 00:12:41.296
The answer is yes,

00:12:41.320 --> 00:12:44.176
that there is a core set of genes
that are involved in both.

00:12:44.200 --> 00:12:47.616
And I'm going to illustrate this
very crudely for maize,

00:12:47.640 --> 00:12:50.056
where the chromosomes below the off switch

00:12:50.080 --> 00:12:53.655
represent all the genes that are required
for desiccation tolerance.

00:12:53.680 --> 00:12:57.936
So as maize seeds dried out
at the end of their period of development,

00:12:57.960 --> 00:12:59.320
they switch these genes on.

00:13:00.680 --> 00:13:03.576
Resurrection plants
switch on the same genes

00:13:03.600 --> 00:13:05.256
when they dry out.

00:13:05.280 --> 00:13:07.056
All modern crops, therefore,

00:13:07.080 --> 00:13:09.136
have these genes
in their roots and leaves,

00:13:09.160 --> 00:13:10.896
they just never switch them on.

00:13:10.920 --> 00:13:12.880
They only switch them on in seed tissues.

00:13:13.440 --> 00:13:15.176
So what we're trying to do right now

00:13:15.200 --> 00:13:17.816
is to understand the environmental
and cellular signals

00:13:17.840 --> 00:13:20.280
that switch on these genes
in resurrection plants,

00:13:21.280 --> 00:13:23.040
to mimic the process in crops.

00:13:23.680 --> 00:13:25.416
And just a final thought.

00:13:25.440 --> 00:13:27.656
What we're trying to do very rapidly,

00:13:27.680 --> 00:13:31.496
is to repeat what nature did
in the evolution of resurrection plants

00:13:31.520 --> 00:13:33.360
some 10 to 40 million years ago.

00:13:34.160 --> 00:13:36.656
My plants and I thank you
for your attention.

00:13:36.680 --> 00:13:40.200
(Applause)