How we can make crops survive without water | Jill Farrant

翻译人员: Gu Yu 校对人员: Tim Lan

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

我认为培育十分耐旱的农作物

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

某种程度上可以保障世界粮食安全

lies in resurrection plants,

而其中的秘诀在于这张

pictured here, in an extremely droughted state.

拍摄于一个非常干旱的州的 图片中的复苏植物。

You might think that these plants look dead,

你也许认为这些植物看起来已经死了

but they're not.

但其实它们没死。

Give them water,

如果给它们水

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

它们将会在12-48小时后 复活，变绿，开始生长。

Now, why would I suggest

现在，为什么我提议

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

培育耐旱的农作物 可以保障粮食安全呢？

Well, the current world population is around 7 billion.

当今世界人口大约为70亿

And it's estimated that by 2050,

预计到2050年，

we'll be between 9 and 10 billion people,

人口将增长至90-100亿，

with the bulk of this growth happening in Africa.

这其中大部分的人口增长在非洲。

The food and agricultural organizations of the world

世界粮农组织

have suggested that we need a 70 percent increase

建议我们在现有基础上 需要将农业产量

in current agricultural practice

提高70%

to meet that demand.

来满足那时的需求。

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

因为植物是食物链的基础，

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

所以增加的产量大部分需要来自植物。

That percentage of 70 percent

但是70%的增量

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

并没有考虑 气候变化所带来的潜在影响。

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

这是戴在2011年 发表的研究报告，

where he took into consideration

里面他考虑了

all the potential effects of climate change

气候变化带来的所有可能的影响

and expressed them -- amongst other things --

然后把它们展现出来 其中就有

increased aridity due to lack of rain or infrequent rain.

由降水缺乏或频率低 所导致的干旱区域增加。

The areas in red shown here,

展示在这里的红色区域

are areas that until recently

是到目前为止

have been very successfully used for agriculture,

农业非常发达

but cannot anymore because of lack of rainfall.

但因为缺少降水 将来不能耕种的地区。

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

这是预计将在 2050年发生的状况。

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

非洲的大部分地区 实际上，全球的大部分地区

is going to be in trouble.

将会陷入困境。

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

我们将不得不想出一些 非常巧妙的方法来生产食物。

And preferably among them, some drought-tolerant crops.

在其中比较合适的方法是 培育一些耐旱的作物

The other thing to remember about Africa is

关于非洲， 我们需要记住的另一件事是

that most of their agriculture is rainfed.

他们的大部分农业主要靠雨水灌溉。

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

现在，培育抗旱作物并非易事。

And the reason for this is water.

其中的原因在于水。

Water is essential to life on this planet.

在这个星球上， 水是对于生命是必不可少的。

All living, actively metabolizing organisms,

所有活着的、代谢旺盛的有机体，

from microbes to you and I,

从微生物到你我，

are comprised predominately of water.

主要由水构成。

All life reactions happen in water.

所有维持生命所需的反应发生在水中。

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

即使丧失少量的水也会导致死亡。

You and I are 65 percent water --

人体65%由水构成

we lose one percent of that, we die.

如果我们其中 丧失1%的水，我们就会死。

But we can make behavioral changes to avoid that.

但是我们可以通过行为的改变 来避免那种情况发生。

Plants can't.

植物却不能。

They're stuck in the ground.

它们生长在地上。

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

所以首先他们比我们含水量更多

about 95 percent water,

大概95%是水分

and they can lose a little bit more than us,

它们也可以比我们多失去一些水

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

不同物种可以短时间内 损失10%到70%

but for short periods only.

的水分。

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

大多数物种都会 抵制或尽量避免失水。

So extreme examples of resistors can be found in succulents.

举一个抗失水者的极端例子：肉质植物

They tend to be small, very attractive,

它们一般很小很漂亮

but they hold onto their water at such great cost

但是它们为了保持水分不得不

that they grow extremely slowly.

生长的十分缓慢。

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

避免失水的主要例子都是乔灌木

They send down very deep roots,

它们的根须深入地下

mine subterranean water supplies

直至地下水资源

and just keep flushing it through them at all times,

不停地吸取大量的地下水

keeping themselves hydrated.

来保持水分。

The one on the right is called a baobab.

右边的植物叫做猴面包树。

It's also called the upside-down tree,

它也被人成为倒置的树

simply because the proportion of roots to shoots is so great

因为根部与地上部分 的比例实在是太夸张

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

以至于这棵树像是倒置的一样。

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

当然了为了保持水分 这样的根部是必须的。

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

也许一年生植物是 最常使用避免失水策略的植物了

Annuals make up the bulk of our plant food supplies.

一年生植物在我的国家的西海岸

Up the west coast of my country,

是我们主要种植的食物来源

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

一年中的绝大部分时间 我们看不到这些蔬菜的生长

But come the spring rains, you get this:

但当春天雨季来临，你可以看到

flowering of the desert.

沙漠之中花开遍地。

The strategy in annuals,

一年生植物的策略

is to grow only in the rainy season.

就是只在雨季生长。

At the end of that season they produce a seed,

在雨季结束的时候 它们产生种子

which is dry, eight to 10 percent water,

种子很干燥， 只含有8%到10%的水

but very much alive.

但却生机勃勃。

And anything that is that dry and still alive,

这样在干燥环境下仍保持活性的性质

we call desiccation-tolerant.

叫做干燥耐受。

In the desiccated state,

在干燥的国家

what seeds can do is lie in extremes of environment

种子在如此极端环境下

for prolonged periods of time.

可以存活很长的一段时间。

The next time the rainy season comes,

下次雨季来临时

they germinate and grow,

它们马上发芽生长

and the whole cycle just starts again.

如此循环往复。

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

普遍认为正是进化出 这样干燥耐受的种子

allowed the colonization and the radiation

才让开花植物和被子植物

of flowering plants, or angiosperms, onto land.

在陆地上的定植和传播成为可能。

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

作为主要食物来源的一年生植物

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

比如构成我们食物来源95% 的小麦，水稻和玉米

And it's been a great strategy

看起来也是一个很好的策略

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

因为短时间内就可以生产大量的种子

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

种子富含可以被人体吸收的能量

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

所以你可以在食物充足的时候 为饥荒做准备。

but there's a downside.

但是也有不足之处。

The vegetative tissues,

这些植物的营养组织

the roots and leaves of annuals,

根部和叶片

do not have much

并没有什么

by way of inherent resistance, avoidance or tolerance characteristics.

抵抗干燥，避免干燥 或者耐受干燥的特性

They just don't need them.

因为它们根本不需要。

They grow in the rainy season

它们本来就生长在雨季

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

而且已经生产了 可以度过余下时间的种子

And so despite concerted efforts in agriculture

而且无论农业专家如何努力

to make crops with improved properties

提升农作物的

of resistance, avoidance and tolerance --

抵抗、避免和耐受干旱的能力

particularly resistance and avoidance

尤其是抵抗和避免干旱的能力

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

尽管我们已经有了 很好的模型来了解植物的运作模式

we still get images like this.

我们仍然只得到了这样的结果。

Maize crop in Africa,

非洲的玉米作物

two weeks without rain

经历两周不下雨之后

and it's dead.

就死了。

There is a solution:

现在有一个方案

resurrection plants.

就是复苏植物。

These plants can lose 95 percent of their cellular water,

这些植物可以失去95%的细胞水分

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

进入干燥的假死状态 长达数月之久

and give them water,

只要给它们水

they green up and start growing again.

它们马上就可以变绿开始生长。

Like seeds, these are desiccation-tolerant.

像种子一样它们拥有干燥耐受性

Like seeds, these can withstand extremes of environmental conditions.

可以忍受极端的环境。

And this is a really rare phenomenon.

这是非常罕见的现象。

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

全世界只有135种 开花植物可以做到。

I'm going to show you a video

我将给各位放一段

of the resurrection process of these three species

三种复苏植物复苏过程

in that order.

的视频。

And at the bottom,

在视频下方

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

有一个时间轴 各位可以看到一切发生得多么迅速。

(Applause)

（掌声）

Pretty amazing, huh?

很神奇 是吧？

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

所以我用了21年时间 研究它们是如何做到的

How do these plants dry without dying?

这些植物如何做到干而不死？

And I work on a variety of different resurrection plants,

因为很多原因我研究了 图中不同的复苏植物

shown here in the hydrated and dry states,

在干燥和有水环境下

for a number of reasons.

的状态

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

其中一个原因是 每一种复苏植物

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

都可以作为一种 农作物的耐旱版本的模板

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

比如左上角这种草

it's called Eragrostis nindensis,

叫做画眉虫草

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

它是苔麸的近亲

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

也就是很多人熟知的 埃塞俄比亚画眉草

it's a staple food in Ethiopia,

那是埃塞俄比亚的主要作物

it's gluten-free,

它不含谷蛋白

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

我们想开发耐旱版本的 埃塞俄比亚画眉草。

The other reason for looking at a number of plants,

另一个我们研究其它各种各样的植物

is that, at least initially,

的原因是，

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

至少我们希望从本质上了解 它们在做同样的事情么？

Do they all use the same mechanisms

它们可以做到失水而不死

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

的内在机制是相同的么？

So I undertook what we call a systems biology approach

所以我采用系统生物学方法

in order to get a comprehensive understanding

希望对植物的耐旱性

of desiccation tolerance,

有一个全面的了解

in which we look at everything

系统生物学方法就是

from the molecular to the whole plant, ecophysiological level.

从分子层面 到整体植株生理生态层面的整体研究

For example we look at things like

比如我们通过解剖

changes in the plant anatomy as they dried out

观察干枯的植物的变化

and their ultrastructure.

和它们的亚显微结构

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

我们观察转录组如何应对干旱 转录组是一个技术术语

in which we look at the genes

意思是我们观察基因开关

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

在应对干旱时是开启还是关闭。

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

大部分基因会制造蛋白质 所以我们研究蛋白质组。

What are the proteins made in response to drying?

干旱来临时植物会制造什么蛋白质？

Some proteins would code for enzymes which make metabolites,

一些蛋白质会制造 让植物新陈代谢的酶

so we look at the metabolome.

所以我们研究代谢组。

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

这很重要 因为植物都是固定在土地之上的

They use what I call a highly tuned chemical arsenal

它们利用所谓的高度协调的化工厂

to protect themselves from all the stresses of their environment.

保护它们不受外界环境的压力。

So it's important that we look

所以研究这些

at the chemical changes involved in drying.

因为干燥引起的 化学变化也非常重要。

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

最后我们在分子层面的研究中

we look at the lipidome --

我们研究了脂质体

the lipid changes in response to drying.

脂质是如何变化的以应对干旱的。

And that's also important

这也很重要

because all biological membranes are made of lipids.

因为所有的生物膜都是脂质的。

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

因为在水中所以它们保持膜状

Take away the water, those membranes fall apart.

脱离水后这些膜就会破碎。

Lipids also act as signals to turn on genes.

脂质同样是开启基因的信号

Then we use physiological and biochemical studies

我们运用生理和生化研究方法

to try and understand the function of the putative protectants

去试验和了解我们已经在

that we've actually discovered in our other studies.

其他研究中发现的假定保护机制。

And then use all of that to try and understand

通过这些所有的研究来尝试理解

how the plant copes with its natural environment.

植物如何适应它周围的自然环境。

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

我的科学哲学是 我需要对耐旱性的机制

of the mechanisms of desiccation tolerance

有全面的理解才可以给出

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

对于生物应用的有意义的建议。

I'm sure some of you are thinking,

我确信有一些人在想

"By biotic application,

“她所说的生物应用

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

是不是意味着转基因作物呢？”

And the answer to that question is:

这个问题的答案是：

depends on your definition of genetic modification.

取决于如何定义转基因。

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

所有我们今天食用的作物 小麦，水稻和玉米

are highly genetically modified from their ancestors,

与祖先植株相比都是高度转基因的，

but we don't consider them GM

我们不认为它们是转基因作物

because they're being produced by conventional breeding.

是因为它们一直 是用传统方式培育的。

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

如果你问我是不是打算把 复苏植物的基因植入作物中

your answer is yes.

我的回答是是的。

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

时间紧迫 我们已经尝试了这些手段

More appropriately, some of my collaborators at UCT,

准确地说 我的一些在UCT的同事

Jennifer Thomson, Suhail Rafudeen,

珍妮弗·汤姆森，萨尔·拉夫德恩

have spearheaded that approach

已经先行进行了实验

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

一会我将展示部分资料。

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

但是我们将要开展的 是一项极具野心的工作

in which we aim to turn on whole suites of genes

我们的目标是启动 已经存在于每棵植株中的

that are already present in every crop.

整套基因

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

它们只是还没有 在极端干旱的环境下被激活

I leave it up to you to decide

我希望各位可以自行判断

whether those should be called GM or not.

这种方式是否属于转基因。

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

我将展示第一阶段实验的部分资料

And in order to do that

在展示之前

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

我需要解释一下 基因工作的原理。

So you probably all know

也许大家都知道

that genes are made of double-stranded DNA.

基因是DNA的双链结构。

It's wound very tightly into chromosomes

它通过紧密的缠绕形成染色体

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

存在于每个人体或者植物的细胞之中

If you unwind that DNA, you get genes.

如果把DNA解缠 你就会得到基因

And each gene has a promoter,

每一个基因有一个启动子

which is just an on-off switch,

即是一个开关

the gene coding region,

基因转录区

and then a terminator,

和终止子

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

这意味着这一部分基因转录结束 下一个基因将要开始转录

Now, promoters are not simple on-off switches.

启动子不是简单的开关

They normally require a lot of fine-tuning,

它们往往需要大量微调

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

在基因开关打开之前 要进行很多的瞄准和修正过程

So what's typically done in biotech studies

所以基本上我们生物技术研究中

is that we use an inducible promoter,

使用诱导型启动子

we know how to switch it on.

来研究如何打开启动子开关

We couple that to genes of interest

我们把它植入我们感兴趣的基因

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

然后把基因植入植株 研究植株的反应。

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

在我接下来展示的研究中

my collaborators used a drought-induced promoter,

我的同事使用了在复苏植物中发现的

which we discovered in a resurrection plant.

干旱诱导蛋白启动子。

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

这个启动子的优势在于不用外界手段

The plant itself senses drought.

植物会自发感受干旱

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

我们使用启动子驱动 复苏植物的抗氧化剂基因

Why antioxidant genes?

为什么是抗氧化剂基因？

Well, all stresses, particularly drought stress,

所有的压力 尤其是干旱的压力

results in the formation of free radicals,

都会形成自由基

or reactive oxygen species,

也就是活性氧。

which are highly damaging and can cause crop death.

活性氧极具破坏力 会直接导致植物死亡。

What antioxidants do is stop that damage.

抗氧化剂可以阻止这种破坏。

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

这是非洲常用的玉米品种

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

箭头左边的是没有这种基因的

to the right --

右边的

plants with the antioxidant genes.

是含有抗氧化基因的植株。

After three weeks without watering,

三周没有浇水之后

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

有抗氧化基因 的植株的状态要好得多。

Now to the final approach.

在实验的最后

My research has shown that there's considerable similarity

因为我的研究已经说明

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

种子和复苏植物的耐旱性的机制 有很多相似之处

So I ask the question,

我的问题是

are they using the same genes?

他们是同一种基因么？

Or slightly differently phrased,

还是略有不同地被修饰过？

are resurrection plants using genes evolved in seed desiccation tolerance

复苏植物是在根部和叶部上 也含有

in their roots and leaves?

这种耐旱基因么？

Have they retasked these seed genes

在复苏植物中

in roots and leaves of resurrection plants?

这些基因 又被根部和叶部重新使用了么？

And I answer that question,

我可以回答这个问题

as a consequence of a lot of research from my group

通过我和我的同事的小组的工作

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

通过来自荷兰的亨克·希尔霍斯特

Mel Oliver in the United States

来自美国的梅尔·奥利弗

and Julia Buitink in France.

和来自法国的朱莉娅布克 的一系列工作

The answer is yes,

我们认为答案是：是的。

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

它们都有一套完整的核心基因

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

我会大概以玉米为例解释一下

where the chromosomes below the off switch

在开关下面的染色体里面有

represent all the genes that are required for desiccation tolerance.

耐旱性必要的全部基因

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

当玉米种子在它们发育的 最后一个阶段面临干燥环境时

they switch these genes on.

开关就会打开。

Resurrection plants switch on the same genes

复苏植物遇到干旱环境是也会

when they dry out.

打开同样的开关。

All modern crops, therefore,

因此所有现代的植物

have these genes in their roots and leaves,

都在它们的根部和叶部 拥有这些基因

they just never switch them on.

只不过它们从来没有打开过开关。

They only switch them on in seed tissues.

它们只在作为种子时打开过开关。

So what we're trying to do right now

我们现在尝试要做的

is to understand the environmental and cellular signals

就是了解打开复苏植物基因开关的

that switch on these genes in resurrection plants,

环境信号和细胞信号

to mimic the process in crops.

并在作物中模仿类似的过程。

And just a final thought.

最后我想说

What we're trying to do very rapidly

我们只是在用飞快的速度重复

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

复苏植物在过去100万年到400万年

some 10 to 40 million years ago.

的大自然中进行的进化。

My plants and I thank you for your attention.

我和我的植物感谢您的关注。

(Applause)

（掌声）