【TED演讲】如何让植物在无水状态下存活？

TED英语演讲课

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演讲题目：How we can make crops survive without water

演讲简介：

随着世界人口的增长和愈加明显的环境改变我们必须用更少的土地养育更多的人。分子生物学家吉尔·法兰特通过研究一种稀有的现象“复苏植物”希望对此有所帮助。复苏植物就是具有超强抵抗干旱能力的植物。它们会带来将来在更加燥热干旱的土地上种植粮食的希望么？

中英文字幕

The strategy in annuals, is to grow only in the rainy season.
一年生植物的策略是只在雨季生长。

At the end of that season they produce a seed, which is dry, eight to 10 percent water, but very much alive.
在雨季结束的时候，它们产生种子，种子很干燥，只含有8%到10%的水，但却生机勃勃。

And anything that is that dry and still alive, we call desiccation-tolerant.
这样在干燥环境下仍保持活性的性质叫做干燥耐受。

In the desiccated state, what seeds can do is lie in extremes of environment for prolonged periods of time.
在干燥的国家种子在如此极端环境下可以存活很长的一段时间。

The next time the rainy season comes, they germinate and grow, and the whole cycle just starts again.
下次雨季来临时，它们马上发芽生长，如此循环往复。

It's widely believed that the evolution of desiccation-tolerant seeds allowed the colonization and the radiation of flowering plants, or angiosperms, onto land.
普遍认为正是进化出这样干燥耐受的种子才让开花植物和被子植物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 because in a short space of time you can produce a lot of seed.
这看起来也是一个很好的策略，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, you can store it in times of plenty for times of famine, but there's a downside.
种子富含可以被人体吸收的能量，所以你可以在食物充足的时候为饥荒做准备，但是也有不足之处。

The vegetative tissues, the roots and leaves of annuals, do not have much by way of inherent resistance, avoidance or tolerance characteristics.
这些植物的营养组织根部和叶片并没有什么抵抗干燥，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 and they've got a seed to help them survive the rest of the year.
它们本来就生长在雨季，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 to make crops with improved properties of resistance,
而且无论农业专家如何努力提升农作物的抵抗、

avoidance and tolerance -- particularly resistance and avoidance because we've had good models to understand how those work -- we still get images like this.
避免和耐受干旱的能力——尤其是抵抗和避免干旱的能力，尽管我们已经有了很好的模型来了解植物的运作模式，我们仍然只得到了这样的结果。

Maize crop in Africa, two weeks without rain and it's dead.
非洲的玉米作物经历两周不下雨之后就死了。

There is a solution: resurrection plants.
现在有一个方案就是复苏植物。

These plants can lose 95 percent of their cellular water, remain in a dry, dead-like state for months to years, and give them water,
这些植物可以失去95%的细胞水分进入干燥的假死状态长达数月之久，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.
就像种子一样，它们可以经受住极端的环境条件。

And this is a really rare phenomenon.
这是一种非常罕见的现象。

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 of the resurrection process of these three species in that order.
我将给各位放一段三种复苏植物复苏过程的视频。

And at the bottom, there's a time axis so you can see how quickly it happens.
在视频下方有一个时间轴，各位可以看到一切发生得多么迅速。

Pretty amazing, huh?
很神奇是吧？

So I've spent the last 21 years trying to understand how they do this.
因此，在过去的21年里，我一直在试图了解它们是如何做到这一点的？

How do these plants dry without dying?
这些植物怎样才能做到干而不死呢？

And I work on a variety of different resurrection plants, shown here in the hydrated and dry states, for a number of reasons.
因为很多原因，我研究了图中不同的复苏植物在干燥和有水环境下的状态。

One of them is that each of these plants serves as a model for a crop that I'd like to make drought-tolerant.
其中一个原因是每一种复苏植物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, it's called Eragrostis nindensis,
比如左上角这种草，叫做画眉虫草，

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 gluten-free,
它是苔麸的近亲，也就是很多人熟知的埃塞俄比亚画眉草，那是埃塞俄比亚的主要作物，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, is that, at least initially, I wanted to find out: do they do the same thing?
另一个我们研究其它各种各样的植物的原因是，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 to be able to lose all that water and not die?
它们可以做到失水而不死的内在机制是相同的么？

So I undertook what we call a systems biology approach in order to get a comprehensive understanding of desiccation tolerance,
所以我采用系统生物学方法，希望对植物的耐旱性有一个全面的了解，

in which we look at everything from the molecular to the whole plant, ecophysiological level.
系统生物学方法就是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 changes in the plant anatomy as they dried out and their ultrastructure.
比如我们通过解剖观察干枯的植物的变化和它们的亚显微结构。

We look at the transcriptome, which is just a term for a technology in which we look at the genes that are switched on or off, in response to drying.
我们观察转录组如何应对干旱，转录组是一个技术术语，意思是我们观察基因开关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, so we look at the metabolome.
一些蛋白质会制造让植物新陈代谢的酶，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 to protect themselves from all the stresses of their environment.
它们利用所谓的高度协调的化工厂保护它们不受外界环境的压力。

So it's important that we look at the chemical changes involved in drying.
所以研究这些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, we look at the lipidome -- the lipid changes in response to drying.
最后我们在分子层面的研究中，我们研究了脂质体脂质是如何变化以应对干旱的。

And that's also important because all biological membranes are made of lipids.
这一点也很重要，因为所有的生物膜都是由脂类组成的。

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 to try and understand the function of the putative protectants that we've actually discovered in our other studies.
我们运用生理和生化研究方法去试验和了解我们已经在其他研究中发现的假定保护机制。

And then use all of that to try and understand how the plant copes with its natural environment.
通过这些所有的研究来尝试理解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 of the mechanisms of desiccation tolerance in order to make a meaningful suggestion for a biotic application.
我的科学哲学是我需要对耐旱性的机制有全面的理解才可以给出对于生物应用的有意义的建议。

I'm sure some of you are thinking, "By biotic application, does she mean she's going to make genetically modified crops?"
我确信有一些人在想“她所说的生物应用是不是意味着转基因作物呢？”

And the answer to that question is: depends on your definition of genetic modification.
这个问题的答案是：取决于如何定义转基因。

All of the crops that we eat today, wheat, rice and maize, are highly genetically modified from their ancestors,
所有我们今天食用的作物小麦，水稻和玉米与祖先植株相比都是高度转基因的，

but we don't consider them GM because they're being produced by conventional breeding.
我们不认为它们是转基因作物，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, your answer is yes.
如果你问我是不是打算把复苏植物的基因植入作物中，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, Jennifer Thomson, Suhail Rafudeen,
准确地说，我的一些在UCT的同事珍妮弗·汤姆森，萨尔·拉夫德恩，

have spearheaded that approach and I'm going to show you some data soon.
他们已经先行进行了实验，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 that are already present in every crop.
我们的目标是启动已经存在于每棵植株中的整套基因。

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 whether those should be called GM or not.
我希望各位可以自行判断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 I have to explain a little bit about how genes work.
在展示之前我需要解释一下基因工作的原理。

So you probably all know that genes are made of double-stranded DNA.
也许大家都知道基因是DNA的双链结构。

It's wound very tightly into chromosomes that are present in every cell of your body or in a plant's body.
它通过紧密的缠绕形成染色体，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, which is just an on-off switch, the gene coding region, and then a terminator,
每一个基因有一个启动子，即是一个开关基因转录区和终止子，

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, lots of things to be present and correct before that gene is switched on.
它们往往需要大量微调，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 is that we use an inducible promoter, we know how to switch it on.
所以基本上，我们生物技术研究中使用诱导型启动子来研究如何打开启动子开关。

We couple that to genes of interest and put that into a plant and see how the plant responds.
我们把它植入我们感兴趣的基因，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, my collaborators used a drought-induced promoter, which we discovered in a resurrection plant.
在我接下来展示的研究中，我的同事使用了在复苏植物中发现的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, results in the formation of free radicals, or reactive oxygen species,
所有的压力尤其是干旱的压力都会形成自由基，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, to the right -- plants with the antioxidant genes.
箭头左边的是没有这种基因的，右边的是含有抗氧化基因的植株。

After three weeks without watering, the ones with the genes do a hell of a lot better.
三周没有浇水之后，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 in the mechanisms of desiccation tolerance in seeds and resurrection plants.
因为我的研究已经说明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, are they using the same genes?
我的问题是他们是同一种基因么？

Or slightly differently phrased, are resurrection plants using genes evolved in seed desiccation tolerance in their roots and leaves?
还是略有不同地被修饰过？复苏植物是在根部和叶部上也含有这种耐旱基因么？

Have they retasked these seed genes in roots and leaves of resurrection plants?
在复苏植物中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 and recent collaborations from a group of Henk Hilhorst in the Netherlands,
通过我和我的同事的小组的工作，通过来自荷兰的亨克·希尔霍斯特，

Mel Oliver in the United States and Julia Buitink in France.
来自美国的梅尔·奥利弗和来自法国的朱莉娅布克的一系列工作，

The answer is yes, that there is a core set of genes that are involved in both.
我们认为答案是：是的，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 represent all the genes that are required for desiccation tolerance.
在开关下面的染色体里面有耐旱性必要的全部基。

So as maize seeds dried out at the end of their period of development, they switch these genes on.
因此当玉米种子在它们发育的最后一个阶段面临干燥环境时开关就会打开。

Resurrection plants switch on the same genes when they dry out.
复苏植物遇到干旱环境是也会打开同样的开关。

All modern crops, therefore, have these genes in their roots and leaves, they just never switch them on.
因此所有现代的植物都在它们的根部和叶部拥有这些基因，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 is to understand the environmental and cellular signals that switch on these genes in resurrection plants,
我们现在尝试要做的就是了解打开复苏植物基因开关的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 is to repeat what nature did in the evolution of resurrection plants some 10 to 40 million years ago.
我们只是在用飞快的速度重复复苏植物在过去100万年到400万年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。

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