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