How we can make crops survive without water | Jill Farrant

譯者: Regina Chu 審譯者: 易帆 余

I believe that the secret to producing extremely drought-tolerant crops,

我相信要培育出極耐旱作物，

which should go some way to providing food security in the world,

為世界糧食安全提供 一定程度的解決之道，

lies in resurrection plants,

秘密在於復甦植物，

pictured here, in an extremely droughted state.

這張圖片顯示它們處在 嚴重乾旱下的狀態。

You might think that these plants look dead,

你們可能會認為 這些植物看起來已經死了，

but they're not.

但並非如此。

Give them water,

給它們水，

and they will resurrect, green up, start growing, in 12 to 48 hours.

它們會在 12 到 48 小時內 復甦、變綠、開始成長。

Now, why would I suggest

為什麼我會說

that producing drought-tolerant crops will go towards providing food security?

培育耐旱作物 可以提供糧食安全？

Well, the current world population is around 7 billion.

目前全世界約有 70 億人口。

And it's estimated that by 2050,

據估計到了 2050 年，

we'll be between 9 and 10 billion people,

我們會有 90 到 100 億人口，

with the bulk of this growth happening in Africa.

大部分的增長會在非洲。

The food and agricultural organizations of the world

世界糧食與農業組織提出，

have suggested that we need a 70 percent increase

依目前的耕作方式， 我們需要 70% 的成長

in current agricultural practice

to meet that demand.

以滿足此需求。

Given that plants are at the base of the food chain,

有鑑於植物位於食物鏈的底層，

most of that's going to have to come from plants.

此增長必須由植物提供。

That percentage of 70 percent

70 % 這樣的百分比數字，

does not take into consideration the potential effects of climate change.

還沒有考慮到 氣候變遷的潛在影響。

This is taken from a study by Dai published in 2011,

這是截自戴研究員 於 2011 年出版的研究報告，

where he took into consideration

他考慮到

all the potential effects of climate change

所有氣候變遷的潛在影響，

and expressed them -- amongst other things --

並陳述，除了其它影響，

increased aridity due to lack of rain or infrequent rain.

因為缺雨或不常下雨， 乾旱情況會加重。

The areas in red shown here,

這裡看到的紅色區域

are areas that until recently

是直到最近

have been very successfully used for agriculture,

都很成功的農業用地，

but cannot anymore because of lack of rainfall.

但無法再使用，因為降雨不足。

This is the situation that's predicted to happen in 2050.

圖上這種情況預計 將於 2050 年發生。

Much of Africa, in fact, much of the world,

非洲大部分地區， 事實上全球大部分區域，

is going to be in trouble.

都會有麻煩。

We're going to have to think of some very smart ways of producing food.

我們不得不想一些 非常高明的方式來生產糧食。

And preferably among them, some drought-tolerant crops.

最好是選耐旱作物。

The other thing to remember about Africa is

非洲有另一件事要記得，

that most of their agriculture is rainfed.

絕大部分的農業都是 看天田（雨養農業）。

Now, making drought-tolerant crops is not the easiest thing in the world.

在這個世界培育 耐旱作物並不容易。

And the reason for this is water.

原因是水。

Water is essential to life on this planet.

水是地球生命的要素。

All living, actively metabolizing organisms,

所有活著、還在代謝的生物，

from microbes to you and I,

舉凡微生物或你我，

are comprised predominately of water.

主要都由水組成。

All life reactions happen in water.

所有的生命反應都在水中發生。

And loss of a small amount of water results in death.

失去一小部分的水 就會導致死亡。

You and I are 65 percent water --

你和我有 65％ 是水，

we lose one percent of that, we die.

只要失去 1% 的水就會死亡。

But we can make behavioral changes to avoid that.

但是我們能改變行為 以避免這種情況。

Plants can't.

植物不能。

They're stuck in the ground.

它們牢牢釘在地上。

And so in the first instance they have a little bit more water than us,

所以首先它們比我們 多含一點水，

about 95 percent water,

大約 95% 都是水，

and they can lose a little bit more than us,

可以比我們多失去一點水分，

like 10 to about 70 percent, depending on the species,

從 10% 到約 70% 都可以， 端看是哪種植物，

but for short periods only.

但是只能短暫失水。

Most of them will either try to resist or avoid water loss.

大部分植物都會想辦法 抗拒或避免失水。

So extreme examples of resistors can be found in succulents.

植物抗拒失水最極端的例子 就是多肉植物。

They tend to be small, very attractive,

它們通常很小、很漂亮，

but they hold onto their water at such great cost

但是它們為了保住水分， 付出了極大的代價，

that they grow extremely slowly.

就是長得奇慢無比。

Examples of avoidance of water loss are found in trees and shrubs.

可以在樹木或灌木中 找到避免失水的例子。

They send down very deep roots,

它們札下深根 ，

mine subterranean water supplies

佈下地網尋找水源，

and just keep flushing it through them at all times,

隨時補注自己，

keeping themselves hydrated.

保持含水狀態。

The one on the right is called a baobab.

右邊這種樹 叫波巴布樹（猢猻樹）。

It's also called the upside-down tree,

又稱為倒栽樹，

simply because the proportion of roots to shoots is so great

就是因為根與莖的比例 差別如此之大，

that it looks like the tree has been planted upside down.

看起來很像倒著種的樹。

And of course the roots are required for hydration of that plant.

當然它的根部 必需讓整棵樹含水。

And probably the most common strategy of avoidance is found in annuals.

大概最常見的避免失水策略 可在一年生植物中看到。

Annuals make up the bulk of our plant food supplies.

一年生植物 佔糧食供給的一大部分。

Up the west coast of my country,

我國西海岸，

for much of the year you don't see much vegetation growth.

一年大部分的時間 都看不到什麼植物生長。

But come the spring rains, you get this:

但是春天一下雨， 你就看到這個：

flowering of the desert.

開花的沙漠。

The strategy in annuals,

一年生植物的策略，

is to grow only in the rainy season.

是只在雨季成長。

At the end of that season they produce a seed,

到了季末它們會結種子，

which is dry, eight to 10 percent water,

種子是乾的， 8% 到 10% 的水，

but very much alive.

但是的確是活的。

And anything that is that dry and still alive,

那麼乾卻還活著的東西，

we call desiccation-tolerant.

我們就稱為耐旱。

In the desiccated state,

在乾燥狀態時，

what seeds can do is lie in extremes of environment

種子能做的就是 靜躺在極端環境下

for prolonged periods of time.

很長一段時間。

The next time the rainy season comes,

下次雨季來時，

they germinate and grow,

就發芽成長，

and the whole cycle just starts again.

生命週期周而復始。

It's widely believed that the evolution of desiccation-tolerant seeds

大家普遍認為 種子的耐旱性演化

allowed the colonization and the radiation

可以使開花植物

of flowering plants, or angiosperms, onto land.

或被子植物，能在陸地上拓殖、輻射。

But back to annuals as our major form of food supplies.

再來談一年生植物 如何成為最主要的糧食來源。

Wheat, rice and maize form 95 percent of our plant food supplies.

小麥、稻米及玉米 佔植物糧食供應量的 95%。

And it's been a great strategy

這是很好的策略，

because in a short space of time you can produce a lot of seed.

因為你可以在短時間內 生產大量的種子。

Seeds are energy-rich so there's a lot of food calories,

種子富含能量， 所以能提供很多卡路里，

you can store it in times of plenty for times of famine,

你可以儲糧以備飢荒，

but there's a downside.

但是有個缺點。

The vegetative tissues,

一年生植物的營養組織，

the roots and leaves of annuals,

根部及葉片，

do not have much

沒有太多

by way of inherent resistance, avoidance or tolerance characteristics.

抗受性、迴避性或耐受性的遺傳特質。

They just don't need them.

它們不需要這些特質。

They grow in the rainy season

它們在雨季生長，

and they've got a seed to help them survive the rest of the year.

然後結種子以幫助它們 撐過一年其餘的日子。

And so despite concerted efforts in agriculture

所以儘管在農業界 大家一致努力

to make crops with improved properties

要改良作物的

of resistance, avoidance and tolerance --

抗受性、迴避性及耐受性，

particularly resistance and avoidance

尤其是抗受性及迴避性，

because we've had good models to understand how those work --

因為我們有很好的範本 瞭解這些如何作用，

we still get images like this.

我們仍然得到像圖上 這樣的結果。

Maize crop in Africa,

非洲的玉米田

two weeks without rain

在兩星期無雨的情況下，

and it's dead.

死亡殆盡。

There is a solution:

我們有一個解決方案：

resurrection plants.

復甦植物。

These plants can lose 95 percent of their cellular water,

這種植物可以失去 細胞內 95% 的水分，

remain in a dry, dead-like state for months to years,

維持在乾燥、近似死亡 狀態下數月到數年，

and give them water,

然後給它們水分，

they green up and start growing again.

它們就會變綠，又開始成長。

Like seeds, these are desiccation-tolerant.

這些就像種子一樣 可以耐旱。

Like seeds, these can withstand extremes of environmental conditions.

這些就像種子一樣 可以禁得起極端環境條件。

And this is a really rare phenomenon.

這是非常罕見的現象。

There are only 135 flowering plant species that can do this.

只有 135 種開花植物 可以做到這點。

I'm going to show you a video

我要給大家看一段影片，

of the resurrection process of these three species

是這三種植物的復甦過程，

in that order.

按圖片上的順序播放。

And at the bottom,

影片下方有時間軸，

there's a time axis so you can see how quickly it happens.

大家可以看到過程有多快。

(Applause)

（掌聲）

Pretty amazing, huh?

很驚人吧？

So I've spent the last 21 years trying to understand how they do this.

我過去 21 年都在 試著瞭解它們如何辦到這一點。

How do these plants dry without dying?

這些植物如何能乾枯卻不死亡？

And I work on a variety of different resurrection plants,

我研究很多種不同的復甦植物，

shown here in the hydrated and dry states,

這裡看到的是含水及乾燥狀態，

for a number of reasons.

有幾個原因。

One of them is that each of these plants serves as a model

其中一個是這裡的 每種植物都充作研究範本，

for a crop that I'd like to make drought-tolerant.

以研究我想培育的耐旱作物。

So on the extreme top left, for example, is a grass,

舉個例子，左上方是一種草，

it's called Eragrostis nindensis,

畫眉草屬植物，

it's got a close relative called Eragrostis tef --

它有個近親叫 衣索比亞畫眉草，

a lot of you might know it as "teff" --

很多人叫它苔麩，

it's a staple food in Ethiopia,

這是衣索比亞國民食物，

it's gluten-free,

無麩質，

and it's something we would like to make drought-tolerant.

我們想讓它耐旱。

The other reason for looking at a number of plants,

另一個原因要看各種植物，

is that, at least initially,

就是，至少起初是這樣，

I wanted to find out: do they do the same thing?

我想知道：是不是 每種植物都有同樣的反應？

Do they all use the same mechanisms

是不是都用同一種機制

to be able to lose all that water and not die?

讓自己失水卻不至於死？

So I undertook what we call a systems biology approach

所以我著手用我們稱為 系統生物學的方法，

in order to get a comprehensive understanding

以期對耐旱性能有完整的瞭解，

of desiccation tolerance,

in which we look at everything

我們看所有的東西，

from the molecular to the whole plant, ecophysiological level.

從分子到全株、 生理生態學階層都看。

For example we look at things like

舉個例子，我們會看像是

changes in the plant anatomy as they dried out

植物在變乾的過程中， 在解剖學上經歷的變化

and their ultrastructure.

及其超微結構。

We look at the transcriptome, which is just a term for a technology

我們會看轉錄組， 這只是一個技術名詞，

in which we look at the genes

基本上就是要看哪些基因

that are switched on or off, in response to drying.

在因應乾燥過程中 會被開啟或關閉。

Most genes will code for proteins, so we look at the proteome.

大部分的基因都製造蛋白質， 所以我們也看蛋白質組。

What are the proteins made in response to drying?

為了因應乾燥， 會製造出哪些蛋白質？

Some proteins would code for enzymes which make metabolites,

有些蛋白質是為了合成酵素， 產生代謝物，

so we look at the metabolome.

所以我們也看代謝物組。

Now, this is important because plants are stuck in the ground.

這很重要， 因為植物牢牢釘在地上。

They use what I call a highly tuned chemical arsenal

它們用我稱為 非常精準的化學兵工廠

to protect themselves from all the stresses of their environment.

來保護自己不受環境逆境影響。

So it's important that we look

所以去看死亡過程的 化學變化就很重要。

at the chemical changes involved in drying.

And at the last study that we do at the molecular level,

我們最近的研究 在看分子層次，

we look at the lipidome --

我們看的是脂類組，

the lipid changes in response to drying.

脂質如何變化以因應死亡。

And that's also important

這也很重要，

because all biological membranes are made of lipids.

因為所有的生物膜 都由脂質組成。

They're held as membranes because they're in water.

它們能形成薄膜是因為在水中。

Take away the water, those membranes fall apart.

把水拿掉，薄膜就會解體。

Lipids also act as signals to turn on genes.

脂質還作為打開基因的信號。

Then we use physiological and biochemical studies

然後我們用生理及生化研究

to try and understand the function of the putative protectants

試著瞭解我們假設的 保護因子的功用，

that we've actually discovered in our other studies.

這些因子是我們 在其它研究中發現的。

And then use all of that to try and understand

然後用所有研究結果 去試著瞭解

how the plant copes with its natural environment.

植物如何適應自然環境。

I've always had the philosophy that I needed a comprehensive understanding

我一直有套哲理， 就是我必須

對耐旱性機制有全盤瞭解，

of the mechanisms of desiccation tolerance

in order to make a meaningful suggestion for a biotic application.

才能對其生物應用 提出有意義的建議。

I'm sure some of you are thinking,

我很確信有些人正在想：

"By biotic application,

「生物應用？

does she mean she's going to make genetically modified crops?"

她是說她要培育基改作物？」

And the answer to that question is:

這個問題的答案是：

depends on your definition of genetic modification.

要看你怎麼定義基改。

All of the crops that we eat today, wheat, rice and maize,

我們今天吃的作物， 小麥、稻米、玉米，

are highly genetically modified from their ancestors,

其基因都已改造成 與原來的老祖宗大不相同，

but we don't consider them GM

但是我們不認為這些是基改，

because they're being produced by conventional breeding.

因為這些是傳統育種的產物，

If you mean, am I going to put resurrection plant genes into crops,

如果你問，我是否要把 復甦作物的基因放進作物中，

your answer is yes.

答案是沒錯。

In the essence of time, we have tried that approach.

時間就是成敗的關鍵， 我們已經試過這種方法。

More appropriately, some of my collaborators at UCT,

更正確的說法是 我在開普敦大學的合作夥伴，

Jennifer Thomson, Suhail Rafudeen,

湯姆森和拉弗丁博士，

have spearheaded that approach

已經帶頭做這種方法，

and I'm going to show you some data soon.

我等一下就會 給大家看一些數據。

But we're about to embark upon an extremely ambitious approach,

但是我們即將用一項 非常有野心的方法，

in which we aim to turn on whole suites of genes

我們的目標是打開一系列基因，

that are already present in every crop.

它們本來就存在於每種作物內。

They're just never turned on under extreme drought conditions.

只是在非常乾旱的情況下 這些基因從未被打開過。

I leave it up to you to decide

我讓大家自己判斷

whether those should be called GM or not.

這該不該稱為基改。

I'm going to now just give you some of the data from that first approach.

我現在就給大家看一下 第一次做的數據。

And in order to do that

為了讓大家明白，

I have to explain a little bit about how genes work.

我必須解釋一下 基因如何運作。

So you probably all know

你們大概都知道

that genes are made of double-stranded DNA.

基因由雙股 DNA 組成。

It's wound very tightly into chromosomes

DNA 緊密纏繞成染色體，

that are present in every cell of your body or in a plant's body.

存在於你或植物體內的 每一個細胞中。

If you unwind that DNA, you get genes.

如果你把 DNA 解開， 就得到基因。

And each gene has a promoter,

每個基因都有一個啟動子，

which is just an on-off switch,

就像開關一樣，

the gene coding region,

還有基因編碼區，

and then a terminator,

及一個終止子，

which indicates that this is the end of this gene, the next gene will start.

表示這是該基因的終點， 下一個基因要開始。

Now, promoters are not simple on-off switches.

啟動子不像開關 那麼簡單。

They normally require a lot of fine-tuning,

它們通常需要很多微調，

lots of things to be present and correct before that gene is switched on.

很多條件必須存在且正確， 基因才會打開。

So what's typically done in biotech studies

所以做生技研究時，

is that we use an inducible promoter,

我們通常使用可誘導型啟動子，

we know how to switch it on.

我們知道如何開啟它。

We couple that to genes of interest

我們將其與要研究的基因配對

and put that into a plant and see how the plant responds.

並放入植物中， 看該植物如何反應。

In the study that I'm going to talk to you about,

在我要跟大家談的這個研究中，

my collaborators used a drought-induced promoter,

我的合作夥伴用一種 由乾旱誘發的啟動子，

which we discovered in a resurrection plant.

我們在復甦植物中發現。

The nice thing about this promoter is that we do nothing.

這個啟動子的好處是 我們不用管它。

The plant itself senses drought.

植物本身會感覺到乾旱。

And we've used it to drive antioxidant genes from resurrection plants.

我們用這個啟動子驅動 復甦植物內的抗氧化基因。

Why antioxidant genes?

為什麼是抗氧化基因？

Well, all stresses, particularly drought stress,

因為所有的逆境， 尤其是乾旱，

results in the formation of free radicals,

都會產生自由基，

or reactive oxygen species,

或活性氧類，

which are highly damaging and can cause crop death.

它們的破壞性極強， 且會導致作物死亡。

What antioxidants do is stop that damage.

抗氧化基因會停止該破壞。

So here's some data from a maize strain that's very popularly used in Africa.

現在看到的是某種玉米品系的數據， 這在非洲極常使用。

To the left of the arrow are plants without the genes,

箭頭左邊的是 沒有該基因的植株，

to the right --

右邊的

plants with the antioxidant genes.

植株有抗氧化基因。

After three weeks without watering,

三星期不澆水後，

the ones with the genes do a hell of a lot better.

有該基因的植株 表現好的不得了。

Now to the final approach.

最後一點。

My research has shown that there's considerable similarity

我的研究顯示

in the mechanisms of desiccation tolerance in seeds and resurrection plants.

種子與復甦植物 耐旱性的機制相當相似。

So I ask the question,

所以我問這個問題，

are they using the same genes?

這兩者都用同樣的基因嗎？

Or slightly differently phrased,

或用略為不同的問法，

are resurrection plants using genes evolved in seed desiccation tolerance

復甦植物會利用 種子的耐旱性基因

在根部與植物上嗎？

in their roots and leaves?

Have they retasked these seed genes

它們會把這些種子基因的任務

in roots and leaves of resurrection plants?

在根部及葉片上利用嗎？

And I answer that question,

我的答案是，

as a consequence of a lot of research from my group

從我的研究小組，

及最近一起合作， 位於荷蘭的希和教授，

and recent collaborations from a group of Henk Hilhorst in the Netherlands,

Mel Oliver in the United States

美國的奧利佛

and Julia Buitink in France.

法國的茱莉亞等 所得的結果，

The answer is yes,

我的答案是有，

that there is a core set of genes that are involved in both.

的確有一組關鍵基因 與兩者都有關。

And I'm going to illustrate this very crudely for maize,

我用這張圖跟大家粗略 說一下玉米的情況，

where the chromosomes below the off switch

開關之下的染色體

represent all the genes that are required for desiccation tolerance.

代表耐旱基因。

So as maize seeds dried out at the end of their period of development,

玉米在種子發育 最後階段要乾掉時，

they switch these genes on.

就會打開這些基因。

Resurrection plants switch on the same genes

復甦植物在乾掉時 也會打開同樣的基因。

when they dry out.

All modern crops, therefore,

因此，所有現代作物

have these genes in their roots and leaves,

根部及葉片內都有這種基因，

they just never switch them on.

只是從來不打開。

They only switch them on in seed tissues.

它們僅打開 種子組織內的這種基因。

So what we're trying to do right now

所以我們現在正在

is to understand the environmental and cellular signals

瞭解環境與細胞信號

that switch on these genes in resurrection plants,

如何打開 復甦植物內的這些基因，

to mimic the process in crops.

並在作物中模擬此過程。

And just a final thought.

最後一點想法。

What we're trying to do very rapidly

我們現在做的就是，

is to repeat what nature did in the evolution of resurrection plants

很快速地重現一千到四千萬年前 大自然復甦植物演化的過程。

some 10 to 40 million years ago.

我的植物和我 都感謝大家的關注。

My plants and I thank you for your attention.

(Applause)

（掌聲）