Crops survive without water By Jill Farrant & comments by Walter Sorochan
Posted on Ted Jan 2016; Posted May 24, 2016
This article and video explain how genetic engineering can help crops grow with a minimum of
water. This information is critical to desert countries, like Africa,
where growing plant food is limited by the shortage of water.
Some readers may have difficulty understanding the presenter, Jill Farrant,
while listening to the video. To help the reader with this possibility, the script is presented below
as an aid to the video.
0:01 [ This number matches the time of the video ] I believe that the secret to producing extremely drought-tolerant crops, which
should go some way to providing food security in the world, lies in resurrection plants, pictured here, in an extremely droughted state.
You might think that these plants look dead, but they're not. Give them water, and they will resurrect, green up, start growing, in 12 to 48 hours.
why would I suggestthat
producing drought-tolerant crops will go towards providing food
the current world population is around 7 billion.And
it's estimated that by 2050,we'll
be between 9 and 10 billion people,with
the bulk of this growth happening in Africa.
food and agricultural organizations of the worldhave
suggested that we need a 70 percent increasein
current agricultural practiceto
meet that demand.Given
that plants are at the base of the food chain,most
of that's going to have to come from plants.
percentage of 70 percentdoes
not take into consideration the potential effects of climate change.
is taken from a study by Dai published in 2011,where
he took into considerationall
the potential effects of climate changeand
expressed them -- amongst other things --increased
aridity due to lack of rain or infrequent rain.The
areas in red shown here,are
areas that until recentlyhave
been very successfully used for agriculture,but
cannot anymore because of lack of rainfall.This
is the situation that's predicted to happen in 2050.Much
of Africa, in fact, much of the world,is
going to be in trouble.We're
going to have to think of some very smart ways of producing food.And
preferably among them, some drought-tolerant crops.
other thing to remember about Africa isthat
most of their agriculture is rainfed.
making drought-tolerant crops is not the easiest thing in the world.And
the reason for this is water.Water
is essential to life on this planet.All
living, actively metabolizing organisms,from
microbes to you and I,are
comprised predominately of water.All
life reactions happen in water.And
loss of a small amount of water results in death.You
and I are 65 percent water --we
lose one percent of that, we die.But
we can make behavioral changes to avoid that.Plants
stuck in the ground.And
so in the first instance they have a little bit more water than us,about
95 percent water,and
they can lose a little bit more than us,like
10 to about 70 percent, depending on the species,but
for short periods only.
of them will either try to resist or avoid water loss.So
extreme examples of resistors can be found in succulents.They
tend to be small, very attractive,but
they hold onto their water at such great costthat
they grow extremely slowly.Examples
of avoidance of water loss are found in trees and shrubs.They
send down very deep roots,mine
subterranean water suppliesand
just keep flushing it through them at all times,keeping
one on the right is called a baobab.It's
also called the upside-down tree,simply
because the proportion of roots to shoots is so greatthat
it looks like the tree has been planted upside down.And
of course the roots are required for hydration of that plant.
probably the most common strategy of avoidance is found in annuals.Annuals
make up the bulk of our plant food supplies.Up
the west coast of my country,for
much of the year you don't see much vegetation growth.But
come the spring rains, you get this:flowering
of the desert.
strategy in annuals,is
to grow only in the rainy season.At
the end of that season they produce a seed,which
is dry, eight to 10 percent water,but
very much alive.And
anything that is that dry and still alive,we
the desiccated state,what
seeds can do is lie in extremes of environmentfor
prolonged periods of time.The
next time the rainy season comes,they
germinate and grow,and
the whole cycle just starts again.
widely believed that the evolution of desiccation-tolerant seedsallowed
the colonization and the radiationof
flowering plants, or angiosperms, onto land.
back to annuals as our major form of food supplies.Wheat,
rice and maize form 95 percent of our plant food supplies.And
it's been a great strategybecause
in a short space of time you can produce a lot of seed.Seeds
are energy-rich so there's a lot of food calories,you
can store it in times of plenty for times of famine,but
there's a downside.The
roots and leaves of annuals, do
not have muchby
way of inherent resistance, avoidance or tolerance characteristics.They
just don't need them.They
grow in the rainy seasonand
they've got a seed to help them survive the rest of the year.
so despite concerted efforts in agricultureto
make crops with improved propertiesof
resistance, avoidance and tolerance --particularly
resistance and avoidancebecause
we've had good models to understand how those work --we
still get images like this.Maize
crop in Africa,two
weeks without rainand
is a solution:resurrection
plants can lose 95 percent of their cellular water,remain
in a dry, dead-like state for months to years,and
give them water,they
green up and start growing again.Like
seeds, these are desiccation-tolerant.Like
seeds, these can withstand extremes of environmental conditions.And
this is a really rare phenomenon.There
are only 135 flowering plant species that can do this.
going to show you a videoof
the resurrection process of these three speciesin
at the bottom,there's
a time axis so you can see how quickly it happens.
I've spent the last 21 years trying to understand how they do this.How
do these plants dry without dying?And
I work on a variety of different resurrection plants,shown
here in the hydrated and dry states,for
a number of reasons.
of them is that each of these plants serves as a modelfor
a crop that I'd like to make drought-tolerant.
on the extreme top left, for example, is a grass,it's
called Eragrostis nindensis,it's
got a close relative called Eragrostis tef --a
lot of you might know it as "teff" --it's
a staple food in Ethiopia,it's
it's something we would like to make drought-tolerant.
other reason for looking at a number of plants,is
that, at least initially,I
wanted to find out: do they do the same thing?Do
they all use the same mechanismsto
be able to lose all that water and not die?
I undertook what we call a systems biology approachin
order to get a comprehensive understandingof
which we look at everythingfrom
the molecular to the whole plant, ecophysiological level.
example we look at things likechanges
in the plant anatomy as they dried outand
look at the transcriptome, which is just a term for a technologyin
which we look at the genesthat
are switched on or off, in response to drying.Most
genes will code for proteins, so we look at the proteome.What
are the proteins made in response to drying?Some
proteins would code for enzymes which make metabolites,so
we look at the metabolome.
this is important because plants are stuck in the ground.They
use what I call a highly tuned chemical arsenalto
protect themselves from all the stresses of their environment.So
it's important that we lookat
the chemical changes involved in drying.
at the last study that we do at the molecular level,we
look at the lipidome --the
lipid changes in response to drying.And
that's also importantbecause
all biological membranes are made of lipids. They're
held as membranes because they're in water.Take
away the water, those membranes fall apart.Lipids
also act as signals to turn on genes.
we use physiological and biochemical studiesto
try and understand the function of the putative protectantsthat
we've actually discovered in our other studies.And
then use all of that to try and understandhow
the plant copes with its natural environment.
always had the philosophy that I needed a comprehensive understandingof
the mechanisms of desiccation tolerancein
order to make a meaningful suggestion for a biotic application.
sure some of you are thinking,"By
she mean she's going to make genetically modified crops?"And
the answer to that question is:depends
on your definition of genetic modification.
of the crops that we eat today, wheat, rice and maize,are
highly genetically modified from their ancestors,but
we don't consider them GMbecause
they're being produced by conventional breeding.If
you mean, am I going to put resurrection plant genes into crops,your
answer is yes.
the essence of time, we have tried that approach.More
appropriately, some of my collaborators at UCT,Jennifer
Thomson, Suhail Rafudeen,have
spearheaded that approachand
I'm going to show you some data soon.
we're about to embark upon an extremely ambitious approach,in
which we aim to turn on whole suites of genesthat
are already present in every crop.They're
just never turned on under extreme drought conditions.I
leave it up to you to decidewhether
those should be called GM or not.
going to now just give you some of the data from that first approach.And
in order to do thatI
have to explain a little bit about how genes work.
you probably all knowthat
genes are made of double-stranded DNA.It's
wound very tightly into chromosomesthat
are present in every cell of your body or in a plant's body.If
you unwind that DNA, you get genes.And
each gene has a promoter,which
is just an on-off switch,the
gene coding region,and
then a terminator,which
indicates that this is the end of this gene, the next gene will start.
promoters are not simple on-off switches.They
normally require a lot of fine-tuning,lots
of things to be present and correct before that gene is switched on.So
what's typically done in biotech studiesis
that we use an inducible promoter,we
know how to switch it on.We
couple that to genes of interestand
put that into a plant and see how the plant responds.
the study that I'm going to talk to you about,my
collaborators used a drought-induced promoter, which
we discovered in a resurrection plant.The
nice thing about this promoter is that we do nothing. The
plant itself senses drought.And
we've used it to drive antioxidant genes from resurrection plants. Why
all stresses, particularly drought stress,results
in the formation of free radicals,or
reactive oxygen species,which
are highly damaging and can cause crop death.What
antioxidants do is stop that damage.
here's some data from a maize strain that's very popularly used in
the left of the arrow are plants without the genes,to
the right --plants
with the antioxidant genes.After
three weeks without watering,the
ones with the genes do a hell of a lot better.
to the final approach.My
research has shown that there's considerable similarityin
the mechanisms of desiccation tolerance in seeds and resurrection
I ask the question,are
they using the same genes?Or
slightly differently phrased,are
resurrection plants using genes evolved in seed desiccation tolerancein
their roots and leaves?Have
they retasked these seed genesin
roots and leaves of resurrection plants?
I answer that question,as
a consequence of a lot of research from my groupand
recent collaborations from a group of Henk Hilhorst in the Netherlands,Mel
Oliver in the United Statesand
Julia Buitink in France.The
answer is yes,that
there is a core set of genes that are involved in both.
I'm going to illustrate this very crudely for maize,where
the chromosomes below the off switch represent
all the genes that are required for desiccation tolerance.So
as maize seeds dried out at the end of their period of development,they
switch these genes on.Resurrection
plants switch on the same geneswhen
they dry out.All
modern crops, therefore,have
these genes in their roots and leaves,they
just never switch them on.They
only switch them on in seed tissues.
what we're trying to do right nowis
to understand the environmental and cellular signalsthat
switch on these genes in resurrection plants,to
mimic the process in crops.
just a final thought.What
we're trying to do very rapidlyis
to repeat what nature did in the evolution of resurrection plantssome
10 to 40 million years ago.
plants and I thank you for your attention.