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防御或生长?美国研究人员让植物同时具备这两种能力

来源:中国科技网 作者:张微编译 2016年08月31日 15:41
[导读] 从自然生态系统到农田,植物面临能量利用的两难境地:为了努力长高,和邻居互相竞争,争夺空间和阳光,或者保护自己抵御害虫和疾病。

防御或生长?美国研究人员让植物同时具备这两种能力 

 

 

从自然生态系统到农田,植物面临能量利用的两难境地:为了努力长高,和邻居互相竞争,争夺空间和阳光,或者保护自己抵御害虫和疾病。 

但是,你能种植出一种植物,让它同时具备这两种能力吗? 

密歇根州立大学的一组研究人员首次完成这一壮举,这一突破性研究对于农民具有重大意义,让他们能够增加作物产量并养活地球上更多的人口。 

“我们创建了一个基因组合,之前没有人做到过,” 密歇根大学基金会生物化学和分子生物学教授,植物科学家格雷格 豪依说,他领导了这项研究。“我们取得了意想不到的结果,这些结果非常有意义。这项研究开辟了新的思路,如何将植物有价值的特征以新颖和有用的方式进行组合。” 

发表在最近出版的《自然通讯》的论文中,豪依(密歇根大学植物研究实验室的一员)和他的研究团队描述了,他们如何在植物中,同时分离出防御激素抑制剂和光受体来修改拟南芥植物(芥菜类)。这种基因改变能够让植物同时具备快速生长和保护自己免受病虫害的能力。 

“通常,植物不能同时具备两种能力。人们普遍认为,植物有固定的能量预算,在一个过程中投入太多,就要以放弃另一个过程作为代价。这是一种成长的权衡,”豪依说。“但是,我们的植物不需要进行权衡,我们已经打乱了这种模式。” 

无论是自然界的植物还是农作物,在生长过程中都受到来自干旱、疾病或昆虫的压力,对了应对,它们都具有防御性的反应,但是同时它们会停止生长或生长缓慢。同样,当植物遇到符合的条件时,它们必须快速生长,如当周围植物和它争夺生存空间时,要争夺阳光,这被称为避荫反应,此时,植物的防御能力就要进行妥协为生长让路。 

“这是成长-防御概念:你要提升防御能力但与此同时你要放弃生长,”豪依说。“生长和防御二者只能取其一。但是,我们通过基因改造,让植物同时具备两种能力。” 

如果该研究能够继续深入,这一突破可能对农业实际应用产生重大意义。如果研究的结果在农作物上进行复制,那么这一成果将对农民产生直接益处,到2050年,能够养活的世界人口将有望达到90亿根据比尔和梅琳达盖茨基金会估计,粮食产量要增加70%100%才能养活不断增长的人口 

“但我们能在农作物上实现这一能力吗——这正是我们努力的方向,”豪依说,这是他下一步研究的目标。 

农民提高作物产量的一个常用的方法是增加种植密度。这会让中耕作物,如玉米或大豆相互竞争的阳光,并降低它们的防御能力,使它们容易受到感染和疾病。为了应对密集种植作物的风险,农民必须使用杀虫剂。 

“如果我们能够设计出更好的玉米植物,它们可以进行防御而不需要杀虫剂,这是该研究潜在的方向,”豪依说。”我们观察到的生长-防御的权衡机制不仅在拟南芥中存在,它在所有植物中都有发现。我们已经修改的激素和光反应路径在所有的主要作物中都存在。” 

该研究由美国能源部资助,在植物中发现了一种在防御信号和光信号的作用之间的联系,这些过程是激活基因应对环境压力的过程。这些令人大开眼界的成果对研究团队来说也是一个惊喜。 

“最初,我对这个研究理念和想法是持怀疑态度的,这想法太疯狂了。但是我们承担了这个风险,并证实这是可行的。”豪依说。“我们种植一种植物,让它做到鱼和熊掌兼得,两全其美。研究成果意义非凡。” 

“英文原文”

Defend or grow? These plants do both 

From natural ecosystems to farmers' fields, plants face a dilemma of energy use: outgrow and outcompete their neighbors for light, or defend themselves against insects and disease. 

But what if you could grow a plant that does both at the same time? 

A team of researchers at Michigan State University is the first to accomplish that feat, and the breakthrough could have fruitful implications for farmers trying to increase crop yields and feed the planet's growing population. 

"We've created a genetic combination that no one has ever made before," said plant scientist Gregg Howe, MSU Foundation professor of biochemistry and molecular biology, who led the study. "We got an unexpected outcome, and these results turned out to be quite interesting. This research may open up new ways of thinking about how valuable plant traits can be combined in novel and useful ways." 

In a paper published in the current issue of Nature Communications, Howe, a member of the Plant Research Lab at MSU, and his team describe how they were able to modify an Arabidopsis plant—a relative of mustard—by "knocking out" both a defense hormone repressor and a light receptor in the plant. This genetic alteration allowed the plant to grow fast and defend itself from insects at the same time. 

"Normally plants can't do both. It is generally thought that plants have a fixed energy budget, and they put that energy toward one process at the expense of other processes. There is a tradeoff," Howe said. "But in our plant there's not an energy tradeoff. We've upset that paradigm." 

Plants in nature and agriculture that are stressed by drought, diseases or insects will mount defensive responses, and at the same time will typically stop growing or grow more slowly. Likewise, when plants are subject to conditions where they must grow fast, such as competing for light when neighbors encroach—called the shade avoidance response—their defenses become compromised. 

"This is the growth-defense concept: you promote defense but at the same time you give up growth," Howe said. "More growth equals less defense, more defense equals less growth. But we've done some genetic trickery to get a plant to do both." 

The implications of this breakthrough could have major practical applications in agriculture as the research continues to develop. If the results of the study can be replicated in crop plants, the work could have direct benefits for farmers trying to feed a world population that is expected to reach nine billion by the year 2050. According to the Bill and Melinda Gates foundation, food production will need to increase by 70 percent to 100 percent to feed that growing population. 

"But can we do this in a crop plant—that is something we want to pursue," said Howe of the next steps in their research. 

One common way for farmers to increase crop yields is to increase the density of their plantings. This leaves row crops—such as corn or soybeans—competing against one another for light, and in doing so lowering their defenses and leaving them susceptible to infestation and disease. To counter these risks of growing densely planted crops, farmers must apply pesticides. 

"If we can design better corn plants, you could pack them in and they would be well defended all the time without pesticides—that's one potential direction this research could go," Howe said. "The growth-defense tradeoffs we've observed aren't something found only in Arabidopsis, it's found in all plants. The hormone and light response pathways we've modified are in all the major crops." 

The research, funded in part by the U.S. Department of Energy, has revealed a connection in plants between the roles played by defense signaling and light signaling, processes that activate genes in response to environmental stresses. Eye-opening results such as these came as a surprise even to the research team. 

"Initially I was skeptical of the research idea and thought 'that's crazy.' But we took the risk and it proved to pay off," Howe said. "We've grown a plant that can have its cake and eat it too. The fact that it can be done is remarkable." 

  

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