How we can make crops survive without water
-
0:01 - 0:05I believe that the secret to producing
extremely drought-tolerant crops, -
0:05 - 0:08which should go some way
to providing food security in the world, -
0:08 - 0:11lies in resurrection plants,
-
0:11 - 0:14pictured here, in an extremely
droughted state. -
0:14 - 0:17You might think
that these plants look dead, -
0:17 - 0:18but they're not.
-
0:18 - 0:20Give them water,
-
0:20 - 0:25and they will resurrect, green up,
start growing, in 12 to 48 hours. -
0:26 - 0:28Now, why would I suggest
-
0:28 - 0:32that producing drought-tolerant crops
will go towards providing food security? -
0:33 - 0:37Well, the current world population
is around 7 billion. -
0:37 - 0:39And it's estimated that by 2050,
-
0:39 - 0:42we'll be between 9 and 10 billion people,
-
0:42 - 0:45with the bulk of this growth
happening in Africa. -
0:46 - 0:48The food and agricultural
organizations of the world -
0:48 - 0:51have suggested that we need
a 70 percent increase -
0:52 - 0:54in current agricultural practice
-
0:54 - 0:55to meet that demand.
-
0:56 - 0:58Given that plants
are at the base of the food chain, -
0:58 - 1:01most of that's going
to have to come from plants. -
1:01 - 1:04That percentage of 70 percent
-
1:04 - 1:08does not take into consideration
the potential effects of climate change. -
1:08 - 1:13This is taken from a study by Dai
published in 2011, -
1:13 - 1:15where he took into consideration
-
1:15 - 1:18all the potential effects
of climate change -
1:18 - 1:20and expressed them --
amongst other things -- -
1:20 - 1:24increased aridity due to lack of rain
or infrequent rain. -
1:24 - 1:26The areas in red shown here,
-
1:26 - 1:28are areas that until recently
-
1:28 - 1:31have been very successfully
used for agriculture, -
1:31 - 1:34but cannot anymore
because of lack of rainfall. -
1:35 - 1:38This is the situation
that's predicted to happen in 2050. -
1:39 - 1:41Much of Africa,
in fact, much of the world, -
1:41 - 1:43is going to be in trouble.
-
1:43 - 1:47We're going to have to think of some
very smart ways of producing food. -
1:47 - 1:50And preferably among them,
some drought-tolerant crops. -
1:50 - 1:52The other thing
to remember about Africa is -
1:52 - 1:55that most of their agriculture is rainfed.
-
1:56 - 2:00Now, making drought-tolerant crops
is not the easiest thing in the world. -
2:00 - 2:02And the reason for this is water.
-
2:02 - 2:05Water is essential to life on this planet.
-
2:05 - 2:09All living, actively
metabolizing organisms, -
2:09 - 2:11from microbes to you and I,
-
2:11 - 2:14are comprised predominately of water.
-
2:14 - 2:16All life reactions happen in water.
-
2:16 - 2:19And loss of a small amount
of water results in death. -
2:19 - 2:21You and I are 65 percent water --
-
2:21 - 2:23we lose one percent of that, we die.
-
2:24 - 2:27But we can make behavioral
changes to avoid that. -
2:28 - 2:29Plants can't.
-
2:30 - 2:31They're stuck in the ground.
-
2:31 - 2:35And so in the first instance they have
a little bit more water than us, -
2:35 - 2:36about 95 percent water,
-
2:36 - 2:38and they can lose
a little bit more than us, -
2:38 - 2:41like 10 to about 70 percent,
depending on the species, -
2:42 - 2:43but for short periods only.
-
2:45 - 2:49Most of them will either try
to resist or avoid water loss. -
2:49 - 2:53So extreme examples of resistors
can be found in succulents. -
2:53 - 2:56They tend to be small, very attractive,
-
2:56 - 2:58but they hold onto their water
at such great cost -
2:58 - 3:00that they grow extremely slowly.
-
3:01 - 3:06Examples of avoidance of water loss
are found in trees and shrubs. -
3:06 - 3:08They send down very deep roots,
-
3:08 - 3:09mine subterranean water supplies
-
3:09 - 3:12and just keep flushing
it through them at all times, -
3:12 - 3:14keeping themselves hydrated.
-
3:14 - 3:16The one on the right is called a baobab.
-
3:16 - 3:18It's also called the upside-down tree,
-
3:18 - 3:22simply because the proportion
of roots to shoots is so great -
3:22 - 3:24that it looks like the tree
has been planted upside down. -
3:24 - 3:28And of course the roots are required
for hydration of that plant. -
3:29 - 3:33And probably the most common strategy
of avoidance is found in annuals. -
3:34 - 3:37Annuals make up the bulk
of our plant food supplies. -
3:37 - 3:39Up the west coast of my country,
-
3:39 - 3:42for much of the year
you don't see much vegetation growth. -
3:42 - 3:45But come the spring rains, you get this:
-
3:45 - 3:46flowering of the desert.
-
3:47 - 3:49The strategy in annuals,
-
3:49 - 3:51is to grow only in the rainy season.
-
3:52 - 3:54At the end of that season
they produce a seed, -
3:54 - 3:57which is dry, eight to 10 percent water,
-
3:57 - 3:59but very much alive.
-
3:59 - 4:02And anything that is
that dry and still alive, -
4:02 - 4:03we call desiccation-tolerant.
-
4:04 - 4:05In the desiccated state,
-
4:05 - 4:08what seeds can do
is lie in extremes of environment -
4:08 - 4:10for prolonged periods of time.
-
4:10 - 4:12The next time the rainy season comes,
-
4:12 - 4:13they germinate and grow,
-
4:13 - 4:15and the whole cycle just starts again.
-
4:16 - 4:20It's widely believed that the evolution
of desiccation-tolerant seeds -
4:20 - 4:22allowed the colonization and the radiation
-
4:22 - 4:26of flowering plants,
or angiosperms, onto land. -
4:27 - 4:30But back to annuals
as our major form of food supplies. -
4:31 - 4:36Wheat, rice and maize form 95 percent
of our plant food supplies. -
4:36 - 4:38And it's been a great strategy
-
4:38 - 4:41because in a short space of time
you can produce a lot of seed. -
4:41 - 4:44Seeds are energy-rich
so there's a lot of food calories, -
4:44 - 4:48you can store it in times of plenty
for times of famine, -
4:48 - 4:50but there's a downside.
-
4:51 - 4:52The vegetative tissues,
-
4:52 - 4:54the roots and leaves of annuals,
-
4:54 - 4:55do not have much
-
4:55 - 5:00by way of inherent resistance,
avoidance or tolerance characteristics. -
5:00 - 5:01They just don't need them.
-
5:01 - 5:02They grow in the rainy season
-
5:02 - 5:06and they've got a seed
to help them survive the rest of the year. -
5:06 - 5:08And so despite concerted
efforts in agriculture -
5:08 - 5:11to make crops with improved properties
-
5:11 - 5:13of resistance, avoidance and tolerance --
-
5:13 - 5:15particularly resistance and avoidance
-
5:15 - 5:18because we've had good models
to understand how those work -- -
5:18 - 5:20we still get images like this.
-
5:20 - 5:22Maize crop in Africa,
-
5:22 - 5:23two weeks without rain
-
5:23 - 5:25and it's dead.
-
5:26 - 5:27There is a solution:
-
5:28 - 5:29resurrection plants.
-
5:29 - 5:33These plants can lose 95 percent
of their cellular water, -
5:33 - 5:37remain in a dry, dead-like state
for months to years, -
5:37 - 5:39and give them water,
-
5:39 - 5:41they green up and start growing again.
-
5:42 - 5:45Like seeds, these are
desiccation-tolerant. -
5:45 - 5:49Like seeds, these can withstand extremes
of environmental conditions. -
5:50 - 5:52And this is a really rare phenomenon.
-
5:52 - 5:56There are only 135 flowering
plant species that can do this. -
5:56 - 5:58I'm going to show you a video
-
5:58 - 6:00of the resurrection process
of these three species -
6:00 - 6:01in that order.
-
6:02 - 6:03And at the bottom,
-
6:03 - 6:06there's a time axis
so you can see how quickly it happens. -
6:44 - 6:46(Applause)
-
6:50 - 6:52Pretty amazing, huh?
-
6:52 - 6:56So I've spent the last 21 years
trying to understand how they do this. -
6:56 - 6:58How do these plants dry without dying?
-
6:59 - 7:02And I work on a variety
of different resurrection plants, -
7:02 - 7:04shown here in the hydrated and dry states,
-
7:04 - 7:06for a number of reasons.
-
7:06 - 7:09One of them is that each
of these plants serves as a model -
7:09 - 7:11for a crop that I'd like
to make drought-tolerant. -
7:11 - 7:14So on the extreme top left,
for example, is a grass, -
7:14 - 7:16it's called Eragrostis nindensis,
-
7:16 - 7:19it's got a close relative
called Eragrostis tef -- -
7:19 - 7:21a lot of you might know it as "teff" --
-
7:21 - 7:22it's a staple food in Ethiopia,
-
7:23 - 7:24it's gluten-free,
-
7:24 - 7:27and it's something we would like
to make drought-tolerant. -
7:27 - 7:29The other reason for looking
at a number of plants, -
7:29 - 7:31is that, at least initially,
-
7:31 - 7:33I wanted to find out:
do they do the same thing? -
7:33 - 7:35Do they all use the same mechanisms
-
7:35 - 7:37to be able to lose
all that water and not die? -
7:37 - 7:40So I undertook what we call
a systems biology approach -
7:40 - 7:42in order to get
a comprehensive understanding -
7:42 - 7:44of desiccation tolerance,
-
7:44 - 7:46in which we look at everything
-
7:46 - 7:49from the molecular to the whole plant,
ecophysiological level. -
7:49 - 7:50For example we look at things like
-
7:50 - 7:53changes in the plant anatomy
as they dried out -
7:53 - 7:54and their ultrastructure.
-
7:54 - 7:57We look at the transcriptome,
which is just a term for a technology -
7:57 - 7:58in which we look at the genes
-
7:58 - 8:01that are switched on or off,
in response to drying. -
8:01 - 8:04Most genes will code for proteins,
so we look at the proteome. -
8:04 - 8:07What are the proteins made
in response to drying? -
8:07 - 8:11Some proteins would code for enzymes
which make metabolites, -
8:11 - 8:13so we look at the metabolome.
-
8:13 - 8:16Now, this is important
because plants are stuck in the ground. -
8:16 - 8:20They use what I call
a highly tuned chemical arsenal -
8:20 - 8:24to protect themselves from all
the stresses of their environment. -
8:24 - 8:25So it's important that we look
-
8:25 - 8:28at the chemical changes
involved in drying. -
8:29 - 8:31And at the last study
that we do at the molecular level, -
8:31 - 8:32we look at the lipidome --
-
8:32 - 8:35the lipid changes in response to drying.
-
8:35 - 8:36And that's also important
-
8:36 - 8:39because all biological membranes
are made of lipids. -
8:39 - 8:41They're held as membranes
because they're in water. -
8:41 - 8:44Take away the water,
those membranes fall apart. -
8:44 - 8:47Lipids also act as signals
to turn on genes. -
8:48 - 8:51Then we use physiological
and biochemical studies -
8:51 - 8:54to try and understand
the function of the putative protectants -
8:54 - 8:57that we've actually discovered
in our other studies. -
8:57 - 8:59And then use all of that
to try and understand -
8:59 - 9:02how the plant copes
with its natural environment. -
9:03 - 9:08I've always had the philosophy that
I needed a comprehensive understanding -
9:08 - 9:10of the mechanisms of desiccation tolerance
-
9:10 - 9:14in order to make a meaningful suggestion
for a biotic application. -
9:15 - 9:17I'm sure some of you are thinking,
-
9:17 - 9:18"By biotic application,
-
9:18 - 9:21does she mean she's going to make
genetically modified crops?" -
9:22 - 9:24And the answer to that question is:
-
9:24 - 9:26depends on your definition
of genetic modification. -
9:27 - 9:30All of the crops that we eat today,
wheat, rice and maize, -
9:30 - 9:33are highly genetically modified
from their ancestors, -
9:33 - 9:35but we don't consider them GM
-
9:35 - 9:38because they're being produced
by conventional breeding. -
9:39 - 9:43If you mean, am I going to put
resurrection plant genes into crops, -
9:43 - 9:44your answer is yes.
-
9:44 - 9:47In the essence of time,
we have tried that approach. -
9:47 - 9:50More appropriately,
some of my collaborators at UCT, -
9:50 - 9:52Jennifer Thomson, Suhail Rafudeen,
-
9:52 - 9:54have spearheaded that approach
-
9:54 - 9:56and I'm going to show you some data soon.
-
9:57 - 10:01But we're about to embark
upon an extremely ambitious approach, -
10:01 - 10:05in which we aim to turn on
whole suites of genes -
10:05 - 10:07that are already present in every crop.
-
10:07 - 10:10They're just never turned on
under extreme drought conditions. -
10:11 - 10:12I leave it up to you to decide
-
10:12 - 10:14whether those should be called GM or not.
-
10:16 - 10:19I'm going to now just give you
some of the data from that first approach. -
10:19 - 10:20And in order to do that
-
10:20 - 10:23I have to explain a little bit
about how genes work. -
10:23 - 10:24So you probably all know
-
10:24 - 10:26that genes are made
of double-stranded DNA. -
10:26 - 10:28It's wound very tightly into chromosomes
-
10:28 - 10:31that are present in every cell
of your body or in a plant's body. -
10:32 - 10:35If you unwind that DNA, you get genes.
-
10:36 - 10:38And each gene has a promoter,
-
10:38 - 10:41which is just an on-off switch,
-
10:41 - 10:42the gene coding region,
-
10:42 - 10:43and then a terminator,
-
10:43 - 10:47which indicates that this is the end
of this gene, the next gene will start. -
10:48 - 10:51Now, promoters are not
simple on-off switches. -
10:51 - 10:53They normally require
a lot of fine-tuning, -
10:53 - 10:57lots of things to be present and correct
before that gene is switched on. -
10:58 - 11:01So what's typically done
in biotech studies -
11:01 - 11:03is that we use an inducible promoter,
-
11:03 - 11:05we know how to switch it on.
-
11:05 - 11:07We couple that to genes of interest
-
11:07 - 11:09and put that into a plant
and see how the plant responds. -
11:10 - 11:13In the study that I'm going
to talk to you about, -
11:13 - 11:15my collaborators used
a drought-induced promoter, -
11:15 - 11:18which we discovered
in a resurrection plant. -
11:18 - 11:21The nice thing about this promoter
is that we do nothing. -
11:21 - 11:23The plant itself senses drought.
-
11:24 - 11:29And we've used it to drive antioxidant
genes from resurrection plants. -
11:29 - 11:31Why antioxidant genes?
-
11:31 - 11:34Well, all stresses,
particularly drought stress, -
11:34 - 11:36results in the formation of free radicals,
-
11:36 - 11:38or reactive oxygen species,
-
11:38 - 11:41which are highly damaging
and can cause crop death. -
11:42 - 11:44What antioxidants do is stop that damage.
-
11:45 - 11:49So here's some data from a maize strain
that's very popularly used in Africa. -
11:49 - 11:53To the left of the arrow
are plants without the genes, -
11:53 - 11:54to the right --
-
11:54 - 11:56plants with the antioxidant genes.
-
11:56 - 11:58After three weeks without watering,
-
11:58 - 12:00the ones with the genes
do a hell of a lot better. -
12:02 - 12:03Now to the final approach.
-
12:03 - 12:07My research has shown
that there's considerable similarity -
12:07 - 12:11in the mechanisms of desiccation tolerance
in seeds and resurrection plants. -
12:11 - 12:12So I ask the question,
-
12:13 - 12:14are they using the same genes?
-
12:14 - 12:17Or slightly differently phrased,
-
12:17 - 12:21are resurrection plants using genes
evolved in seed desiccation tolerance -
12:21 - 12:23in their roots and leaves?
-
12:23 - 12:25Have they retasked these seed genes
-
12:25 - 12:27in roots and leaves
of resurrection plants? -
12:28 - 12:30And I answer that question,
-
12:30 - 12:32as a consequence of a lot
of research from my group -
12:32 - 12:36and recent collaborations from a group
of Henk Hilhorst in the Netherlands, -
12:36 - 12:37Mel Oliver in the United States
-
12:37 - 12:40and Julia Buitink in France.
-
12:40 - 12:41The answer is yes,
-
12:41 - 12:44that there is a core set of genes
that are involved in both. -
12:44 - 12:48And I'm going to illustrate this
very crudely for maize, -
12:48 - 12:50where the chromosomes below the off switch
-
12:50 - 12:54represent all the genes that are required
for desiccation tolerance. -
12:54 - 12:58So as maize seeds dried out
at the end of their period of development, -
12:58 - 12:59they switch these genes on.
-
13:01 - 13:04Resurrection plants
switch on the same genes -
13:04 - 13:05when they dry out.
-
13:05 - 13:07All modern crops, therefore,
-
13:07 - 13:09have these genes
in their roots and leaves, -
13:09 - 13:11they just never switch them on.
-
13:11 - 13:13They only switch them on in seed tissues.
-
13:13 - 13:15So what we're trying to do right now
-
13:15 - 13:18is to understand the environmental
and cellular signals -
13:18 - 13:20that switch on these genes
in resurrection plants, -
13:21 - 13:23to mimic the process in crops.
-
13:24 - 13:25And just a final thought.
-
13:25 - 13:28What we're trying to do very rapidly
-
13:28 - 13:31is to repeat what nature did
in the evolution of resurrection plants -
13:32 - 13:33some 10 to 40 million years ago.
-
13:34 - 13:37My plants and I thank you
for your attention. -
13:37 - 13:43(Applause)
- Title:
- How we can make crops survive without water
- Speaker:
- Jill Farrant
- Description:
-
As the world's population grows and the effects of climate change come into sharper relief, we'll have to feed more people using less arable land. Molecular biologist Jill Farrant studies a rare phenomenon that may help: "resurrection plants" -- super-resilient plants that seemingly come back from the dead. Could they hold promise for growing food in our coming hotter, drier world?
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 13:56
Brian Greene edited English subtitles for How we can make crops survive without water | ||
Brian Greene edited English subtitles for How we can make crops survive without water | ||
Brian Greene edited English subtitles for How we can make crops survive without water | ||
Brian Greene edited English subtitles for How we can make crops survive without water | ||
Brian Greene approved English subtitles for How we can make crops survive without water | ||
Brian Greene edited English subtitles for How we can make crops survive without water | ||
Brian Greene edited English subtitles for How we can make crops survive without water | ||
Brian Greene edited English subtitles for How we can make crops survive without water |