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This is Scientific American's 60-second Science, I'm Christine Herman.
Tobacco plants of, course, are grown to make cigarettes. But tobacco is also used a lot in scientific research. And a new study shows tobacco can be genetically engineered to churn out large amounts of a commercially important bacterial enzyme known as cellulase. The enzyme has many industrial uses, including as an agent in the production of biofuel.
And even while their plant machinery is being co-opted as an enzyme-making factory, the plants suffer no reduction in yield while grown out in the field compared with unaltered plants. That fact is rather remarkable, because you might suspect that when a plant is expending resources to create large amounts of cellulase it would struggle to grow. But that's not the case here.
The proof-of-concept study is in the journal Nature Plants.
University of Illinois plant biologist Justin McGrath is a co-lead author of the study. He says the work could lead to lower costs for producing useful proteins like enzymes and some vaccines. That's because it can be way cheaper to cultivate tobacco plants in a field than to grow genetically modified yeast and other microbes indoors in large fermenters. Here's McGrath:
"Our estimates from this study are that it would cost between 20 cents and one dollar to produce a gram of this cellulase, whereas current methods, depending on the type of method you're using, could cost from a couple hundred dollars to a couple thousand dollars."
Growing such plants in the field rather than indoors also makes it much easier to pursue really large-scale production of medicinal and industrial proteins.
But any time you talk about growing genetically modified plants out in open areas, there's a concern that the DNA inserted into the crop could escape and find its way into other organisms. But the researchers safeguard the system against such an incident by avoiding the cell nucleus, where DNA is available to be duplicated and passed along. Instead, they modified the DNA in the chloroplasts—organelles responsible for photosynthesis, not reproduction.
"That adds a very nice safety feature." Rainer Fischer, a veteran biotechnology researcher at Purdue University. He wasn't involved in this study. "So basically you don't have any chloroplasts in tobacco pollen, so there should be no danger for outcrossing" — that is, no foreseeable risk of having the foreign DNA find its way into other plants in nature.
Further research will determine if this system can work to produce other valuable enzymes, which could help transform the tobacco plant from health enemy to ally.
Thanks for listening for Scientific American — 60-Second Science. I'm Christine Herman.
參考譯文
這裡是科學美國人——60秒科學系列，我是克裡斯汀·赫爾曼。
人們種植菸草植物自然是用來製作香菸的。但菸草也大量應用於科學研究。一項新研究表明，菸草能被基因改造，以大量生產一種在商業上非常重要的細菌酶——纖維素酶。這種酶有多種工業用途，包括作為生物燃料生產的製劑。
經改造後，即使菸草的植物機制被選為製造酶的工廠，與未經改造的菸草相比，其在野外生長時產量也不會降低。這一事實相當引人注目，因為你可能會懷疑，當植物消耗大量資源來創造大量纖維素酶時，它會難以生長。但這裡的情況並非如此。
這項概念驗證研究發表在《自然·植物》期刊上。
伊利諾伊大學的植物生物學家賈斯汀·麥克格拉斯是這項研究的其中一個主要作者。他表示，這項研究可以降低酶和某些疫苗等有用蛋白質的生產成本。這是因為在野外種植菸草，比在室內大型發酵桶中培養轉基因酵母和其他微生物要便宜得多。下面是麥克斯拉斯所說：
「我們通過這項研究估計，生產1克這種纖維素酶的成本在20美分到1美元之間，而目前的方法，依據你所使用的方法類型，可能會花費數百至數千美元。」
在野外而不是室內種植這些菸草，還可以使人們更容易獲得大規模生產的藥用和工業蛋白質。
但每次你在開放區域種植轉基因作物，人們就會擔心，植入作物中的DNA會逃跑，進到其他生物體中。但研究人員通過避開細胞核來保護該系統免遭此類事件，細胞核是DNA進行複製和傳遞的場所。相反，他們修改了葉綠體中的DNA，葉綠體是負責光合作用而不是繁殖的細胞器。
「這增加了一個非常好的安全特徵。」普渡大學的資深生物技術研究員萊納·費舍爾說到。他並未參與這項研究。「因此，菸草花粉中基本上沒有任何葉綠體，所以應該也不會有異型雜交的風險」——也就是說，就外來DNA進入自然界中其他植物來說，目前沒有可預見的風險。
進一步研究將確定該系統能否產生其他有價值的酶，這可能有助於將菸草從健康敵人轉變為盟友。
謝謝大家收聽科學美國人——60秒科學。我是克裡斯汀·赫爾曼。