Genetic engineers are applying their skills to tropical crops
EVERY hectare of paddy[1] fields in Asia provides enough rice to feed 27 people. Fifty years from now, according to some projections, each hectare will have to cater[2] for 43. Converting more land to paddy is not an option, since suitable plots are already in short supply. In fact, in many of the continent's most fertile river basins, urban sprawl is consuming growing quantities of prime rice-farming land. Moreover, global warming is likely to make farmers' lives increasingly difficult, by causing more frequent droughts in some places and worse flooding in others. （1）Scientists at the International Rice Research Institute （IRRI） doubt it is possible to improve productivity as much as is needed through better farming practices or the adoption of new strains derived from conventional cross-breeding. Instead, they aim to improve rice yields by 50% using modern genetic techniques.
在亞洲，每公頃稻田產(chǎn)出的大米可夠養(yǎng)活27個人。據(jù)預(yù)測，50年后每公頃稻田將必須為43個人供應(yīng)口糧。由于可耕地本來就不足，因此將更多的土地變成稻田并不可取。事實上，在亞洲大陸許多非常肥沃的江河流域，城市擴張正在吞噬越來越多最適于種植水稻的土地。此外，全球氣候變暖由于造成一些地方干旱頻發(fā)和其它地方水澇加重而使得農(nóng)民的生活日益艱難。國際水稻研究所（IRRI）的科學(xué)家認(rèn)為，單靠優(yōu)化耕作方式或采用常規(guī)雜交技術(shù)培育的新品種不可能進一步增加產(chǎn)量，相反，他們打算利用現(xiàn)代遺傳修飾技術(shù)使水稻增產(chǎn)50%.
On December 4th the Consultative Group on International Agricultural Research （CGIAR）, a network of research institutes of which IRRI is a member, unveiled a series of schemes intended to protect crop yields against the ill effects of global warming. Many involve genetic engineering—which is generally embraced by farmers in poor countries even if some Western consumers turn their noses up at it. Some, though, only use genetics to identify useful genes. （2）For example, IRRI's scientists have found a gene that allows an Indian rice strain to survive total immersion[3] for several weeks, and have cross-bred it into a strain favoured by farmers in flood-prone Bangladesh. In trials, the new plant produced as much rice as the original under normal conditions, but over twice as much after prolonged flooding. This trait could increase the world's rice harvest dramatically, since flooding damages some 20m hectares （50m acres） of rice each year out of a total crop of 150m hectares.
12月4日，國際農(nóng)業(yè)研究磋商組織（CGIAR，一個研究系統(tǒng)，IRRI是其下屬的研究所之一）披露了一系列旨在保護糧食產(chǎn)量免受全球氣候變暖不利影響的方案，其中多數(shù)與基因工程有關(guān)（即使有些西方消費者拒絕接受經(jīng)基因工程改良的糧食，但落后國家的農(nóng)民還是廣泛采用了此項技術(shù)），不過有的只是運用遺傳學(xué)方法確定有益基因。例如，IRRI科學(xué)家已經(jīng)發(fā)現(xiàn)了一種基因，它使一種印度水稻在被水完全淹沒的環(huán)境下仍能存活數(shù)周?？茖W(xué)家將其與一種在易發(fā)洪澇的孟加拉國深受農(nóng)民青睞的水稻進行了雜交。試種表明，新品種大米產(chǎn)量正常條件下與原品種產(chǎn)量相當(dāng)，但在長時間洪澇后則是原品種產(chǎn)量的兩倍多。鑒于全球總共1.5億公頃農(nóng)作物中每年大約有2千萬公頃（5千萬英畝）遭受洪澇破壞，這一特性有可能大幅度提高全球水稻收成。
By far the most ambitious project on CGIAR's list, though, involves transforming the way in which rice photosynthesises. That will require some serious genetic restructuring.
不過就目前而言，CGIAR開展的研究項目中有挑戰(zhàn)性的還是改變水稻光合作用的途徑，這就必須進行一絲不茍的基因重組。
Three into four will go 將C3變成C4就行
Most plants use an enzyme called rubisco to convert carbon dioxide （CO2） into sugars containing three carbon atoms—a process known as C3 photosynthesis. But at temperatures above 25°C, rubisco begins to bond with oxygen instead of CO2, reducing the efficiency of the reaction. As a result, certain plants in warm climates have evolved a different mechanism, called C4 photosynthesis, in which other enzymes help to concentrate CO2 around the rubisco, and the initial result is a four-carbon sugar. In hot, sunny climes, these C4 plants are half as efficient again as their C3 counterparts. They also use less water and nitrogen. The result, in the case of staple crops, is higher yields in tougher conditions: a hectare of rice, a C3 plant, produces a harvest of no more than eight tonnes, whereas maize, a C4 plant, yields as much as 12 tonnes.
大多數(shù)植物利用核酮糖-1，5二磷酸羧化酶加氧酶 （rubisco） 將二氧化碳（CO2）轉(zhuǎn)化成含有3個碳原子的糖類，此過程即C3光合作用。但當(dāng)溫度超過25°C時，rubisco就不再與CO2結(jié)合，而開始結(jié)合氧分子，從而降低了光合效率。因此，處于溫暖氣候條件下的某些植物就進化產(chǎn)生不同的光合作用，即C4光合作用。在此作用過程中，其它酶類可促進CO2聚集到rubisco周圍，反應(yīng)生成的初始產(chǎn)物是四碳糖類。在炎熱、陽光充足的氣候下，這些C4植物光合效率比C3植物要高50％。此外，C4植物對水和氮氣的需要量也較少。結(jié)果是，就主要作物而言，在較為惡劣的環(huán)境下產(chǎn)量比較高——一公頃的水稻（C3植物）產(chǎn)量最多為8噸，而一公頃的玉米（C4植物）產(chǎn)量可達12噸。
Turning a C3 plant into a C4 one, though, is trickier than conferring flood resistance, since it involves wholesale changes in anatomy. C4 plants often absorb CO2 from the air in one type of cell and then convert it to sugars through photosynthesis in another. C3 plants, by contrast, do both jobs in the same place.
不過，將C3植物轉(zhuǎn)化成C4植物由于涉及無數(shù)的結(jié)構(gòu)變化，因此比培育抗?jié)称贩N要更為復(fù)雜。C4植物常常將空氣中的CO2吸入到某一類細胞中，然后再在另一類細胞中利用光合作用將其轉(zhuǎn)化為糖類。相比之下，C3植物則是在同一類細胞中完成這兩個步驟。
（3）On the other hand, C4 photosynthesis seems to have evolved more than 50 times, in 19 families of plant. That variety suggests the shift from one form of photosynthesis to the other is not as radical as might appear at first sight. It also gives researchers a number of starting points for the project. Some C4 plants, for example, absorb CO2 and photosynthesise it at either end of special elongated[4] cells, instead of separating the functions out into two different types of cell. Many C3 plants, meanwhile, have several of the genes needed for C4 photosynthesis, but do not use them in the same way. In fact, the distinction between C3 and C4 plants is not always clear-cut. Some species use one method in their leaves and the other in their stems.
此外，C4光合作用可見于19科植物中，至今可能經(jīng)歷了50次以上的進化。這么多次的進化表明，從一種形式的光合作用轉(zhuǎn)化為另一形式的光合作用并不怎么“干凈利落”。這也為研究人員提供了許多關(guān)于該研究的切入點。比如說，有的C4植物對CO2的吸收和光合都是分別在某一類長形的特殊細胞兩端進行，而非分散到兩類不同的細胞中。同時許多C3植物都含有數(shù)種C4光合作用必需的基因，但利用方式均不相同。實際上，C3與C4植物并非總是有著明顯的區(qū)別。有的植物在其葉部利用一種光合機制，而在其莖部利用的又是另一種光合機制。
John Sheehy, one of IRRI's crop scientists, plans to screen the institute's collection of 6,000 varieties of wild rice to see if any of them display a predisposition for C4 photosynthesis. Other researchers, meanwhile, are trying to isolate the genes responsible for C4 plants' unusual anatomy and biochemistry. A few years ago, geneticists managed to get rice to produce one of the enzymes needed for C4 photosynthesis by transplanting the relevant gene from maize.
IRRI農(nóng)作物科學(xué)家之一約翰?希伊計劃對該研究所收集的6000種野生水稻進行篩選，以弄清哪些品種易于進行C4光合作用。與此同時其他研究人員正致力于分離決定C4植物異常結(jié)構(gòu)和生化特性的基因。幾年前，遺傳學(xué)家通過將玉米中的相關(guān)基因轉(zhuǎn)入水稻，從而在水稻中成功合成了C4光合作用必需酶的一種。
（4）The task, admits Robert Zeigler, IRRI's director, is daunting, and will take ten years or more. But the potential is enormous. Success would not only increase yields, but also reduce the need for water and fertilisers, since C4 plants make more efficient use of both. Other important C3 crops, such as wheat, sweet potatoes and cassava[5], could also benefit. If it all works, a second green revolution beckons.
IRRI負責(zé)人羅伯特?齊格勒承認(rèn)此項任務(wù)十分艱巨，將需要十年以上的時間才能完成，不過潛力是巨大的。由于C4植物能更為高效地利用兩種光合作用，因此研究一旦成功不但會增加水稻產(chǎn)量，而且會減少對水和肥料的需求量。其他重要的C3植物如小麥、甜薯、甜瓜等也會受益。假如一切順利，就將標(biāo)志著第二次綠色革命的到來。
[NOTES]（OXFORD）
1. paddy n. （also `paddy-field） [C] field where rice is grown 稻田. 2 [U] rice that is still growing or in the husk 稻; 稻谷.
2. cater v. 1 （a） [I, Ipr] ~ （for sth/sb） provide food and services, esp at social functions 提供飲食及服務(wù)（尤指社交方面）: cater for a party, banquet, etc 為聚會、 宴會等備辦食物 * Fifty is a lot of people to cater for! 承辦五十人的飲食可夠多的! （b） [Tn] （esp US） provide food and services for （a party, banquet, etc） 為（聚會、 宴會等）提供飲食及服務(wù). 2 [Ipr] （a） ~ for sb/sth provide what is needed or desired by sb/sth 由某人[某事物]提供、 迎合: TV must cater for many different tastes. 電視節(jié)目必須迎合各種人的愛好. （b） ~ to sth try to satisfy a particular need or demand 滿足某種需要或要求: newspapers catering to people's love of scandal 迎合人們愛看丑聞消息的報紙.
3. immersion n. [U] 1 immersing; being immersed 沉浸; 浸沉. 2 baptism by putting the whole body under water 洗禮; 浸禮. immersion heater electric heater fixed inside a hot-water tank in a home 浸入式加熱器（家庭用的）.
4. elongated adj. （made） long and thin; stretched out （被拉得）細長的; 伸長的: elongated figures in a painting 畫中的細長的人.
5. cassava n. 1 [C] tropical plant with starchy roots 木薯. 2 [U] starch or flour obtained from these roots, used to make tapioca 木薯粉.
EVERY hectare of paddy[1] fields in Asia provides enough rice to feed 27 people. Fifty years from now, according to some projections, each hectare will have to cater[2] for 43. Converting more land to paddy is not an option, since suitable plots are already in short supply. In fact, in many of the continent's most fertile river basins, urban sprawl is consuming growing quantities of prime rice-farming land. Moreover, global warming is likely to make farmers' lives increasingly difficult, by causing more frequent droughts in some places and worse flooding in others. （1）Scientists at the International Rice Research Institute （IRRI） doubt it is possible to improve productivity as much as is needed through better farming practices or the adoption of new strains derived from conventional cross-breeding. Instead, they aim to improve rice yields by 50% using modern genetic techniques.
在亞洲，每公頃稻田產(chǎn)出的大米可夠養(yǎng)活27個人。據(jù)預(yù)測，50年后每公頃稻田將必須為43個人供應(yīng)口糧。由于可耕地本來就不足，因此將更多的土地變成稻田并不可取。事實上，在亞洲大陸許多非常肥沃的江河流域，城市擴張正在吞噬越來越多最適于種植水稻的土地。此外，全球氣候變暖由于造成一些地方干旱頻發(fā)和其它地方水澇加重而使得農(nóng)民的生活日益艱難。國際水稻研究所（IRRI）的科學(xué)家認(rèn)為，單靠優(yōu)化耕作方式或采用常規(guī)雜交技術(shù)培育的新品種不可能進一步增加產(chǎn)量，相反，他們打算利用現(xiàn)代遺傳修飾技術(shù)使水稻增產(chǎn)50%.
On December 4th the Consultative Group on International Agricultural Research （CGIAR）, a network of research institutes of which IRRI is a member, unveiled a series of schemes intended to protect crop yields against the ill effects of global warming. Many involve genetic engineering—which is generally embraced by farmers in poor countries even if some Western consumers turn their noses up at it. Some, though, only use genetics to identify useful genes. （2）For example, IRRI's scientists have found a gene that allows an Indian rice strain to survive total immersion[3] for several weeks, and have cross-bred it into a strain favoured by farmers in flood-prone Bangladesh. In trials, the new plant produced as much rice as the original under normal conditions, but over twice as much after prolonged flooding. This trait could increase the world's rice harvest dramatically, since flooding damages some 20m hectares （50m acres） of rice each year out of a total crop of 150m hectares.
12月4日，國際農(nóng)業(yè)研究磋商組織（CGIAR，一個研究系統(tǒng)，IRRI是其下屬的研究所之一）披露了一系列旨在保護糧食產(chǎn)量免受全球氣候變暖不利影響的方案，其中多數(shù)與基因工程有關(guān)（即使有些西方消費者拒絕接受經(jīng)基因工程改良的糧食，但落后國家的農(nóng)民還是廣泛采用了此項技術(shù)），不過有的只是運用遺傳學(xué)方法確定有益基因。例如，IRRI科學(xué)家已經(jīng)發(fā)現(xiàn)了一種基因，它使一種印度水稻在被水完全淹沒的環(huán)境下仍能存活數(shù)周?？茖W(xué)家將其與一種在易發(fā)洪澇的孟加拉國深受農(nóng)民青睞的水稻進行了雜交。試種表明，新品種大米產(chǎn)量正常條件下與原品種產(chǎn)量相當(dāng)，但在長時間洪澇后則是原品種產(chǎn)量的兩倍多。鑒于全球總共1.5億公頃農(nóng)作物中每年大約有2千萬公頃（5千萬英畝）遭受洪澇破壞，這一特性有可能大幅度提高全球水稻收成。
By far the most ambitious project on CGIAR's list, though, involves transforming the way in which rice photosynthesises. That will require some serious genetic restructuring.
不過就目前而言，CGIAR開展的研究項目中有挑戰(zhàn)性的還是改變水稻光合作用的途徑，這就必須進行一絲不茍的基因重組。
Three into four will go 將C3變成C4就行
Most plants use an enzyme called rubisco to convert carbon dioxide （CO2） into sugars containing three carbon atoms—a process known as C3 photosynthesis. But at temperatures above 25°C, rubisco begins to bond with oxygen instead of CO2, reducing the efficiency of the reaction. As a result, certain plants in warm climates have evolved a different mechanism, called C4 photosynthesis, in which other enzymes help to concentrate CO2 around the rubisco, and the initial result is a four-carbon sugar. In hot, sunny climes, these C4 plants are half as efficient again as their C3 counterparts. They also use less water and nitrogen. The result, in the case of staple crops, is higher yields in tougher conditions: a hectare of rice, a C3 plant, produces a harvest of no more than eight tonnes, whereas maize, a C4 plant, yields as much as 12 tonnes.
大多數(shù)植物利用核酮糖-1，5二磷酸羧化酶加氧酶 （rubisco） 將二氧化碳（CO2）轉(zhuǎn)化成含有3個碳原子的糖類，此過程即C3光合作用。但當(dāng)溫度超過25°C時，rubisco就不再與CO2結(jié)合，而開始結(jié)合氧分子，從而降低了光合效率。因此，處于溫暖氣候條件下的某些植物就進化產(chǎn)生不同的光合作用，即C4光合作用。在此作用過程中，其它酶類可促進CO2聚集到rubisco周圍，反應(yīng)生成的初始產(chǎn)物是四碳糖類。在炎熱、陽光充足的氣候下，這些C4植物光合效率比C3植物要高50％。此外，C4植物對水和氮氣的需要量也較少。結(jié)果是，就主要作物而言，在較為惡劣的環(huán)境下產(chǎn)量比較高——一公頃的水稻（C3植物）產(chǎn)量最多為8噸，而一公頃的玉米（C4植物）產(chǎn)量可達12噸。
Turning a C3 plant into a C4 one, though, is trickier than conferring flood resistance, since it involves wholesale changes in anatomy. C4 plants often absorb CO2 from the air in one type of cell and then convert it to sugars through photosynthesis in another. C3 plants, by contrast, do both jobs in the same place.
不過，將C3植物轉(zhuǎn)化成C4植物由于涉及無數(shù)的結(jié)構(gòu)變化，因此比培育抗?jié)称贩N要更為復(fù)雜。C4植物常常將空氣中的CO2吸入到某一類細胞中，然后再在另一類細胞中利用光合作用將其轉(zhuǎn)化為糖類。相比之下，C3植物則是在同一類細胞中完成這兩個步驟。
（3）On the other hand, C4 photosynthesis seems to have evolved more than 50 times, in 19 families of plant. That variety suggests the shift from one form of photosynthesis to the other is not as radical as might appear at first sight. It also gives researchers a number of starting points for the project. Some C4 plants, for example, absorb CO2 and photosynthesise it at either end of special elongated[4] cells, instead of separating the functions out into two different types of cell. Many C3 plants, meanwhile, have several of the genes needed for C4 photosynthesis, but do not use them in the same way. In fact, the distinction between C3 and C4 plants is not always clear-cut. Some species use one method in their leaves and the other in their stems.
此外，C4光合作用可見于19科植物中，至今可能經(jīng)歷了50次以上的進化。這么多次的進化表明，從一種形式的光合作用轉(zhuǎn)化為另一形式的光合作用并不怎么“干凈利落”。這也為研究人員提供了許多關(guān)于該研究的切入點。比如說，有的C4植物對CO2的吸收和光合都是分別在某一類長形的特殊細胞兩端進行，而非分散到兩類不同的細胞中。同時許多C3植物都含有數(shù)種C4光合作用必需的基因，但利用方式均不相同。實際上，C3與C4植物并非總是有著明顯的區(qū)別。有的植物在其葉部利用一種光合機制，而在其莖部利用的又是另一種光合機制。
John Sheehy, one of IRRI's crop scientists, plans to screen the institute's collection of 6,000 varieties of wild rice to see if any of them display a predisposition for C4 photosynthesis. Other researchers, meanwhile, are trying to isolate the genes responsible for C4 plants' unusual anatomy and biochemistry. A few years ago, geneticists managed to get rice to produce one of the enzymes needed for C4 photosynthesis by transplanting the relevant gene from maize.
IRRI農(nóng)作物科學(xué)家之一約翰?希伊計劃對該研究所收集的6000種野生水稻進行篩選，以弄清哪些品種易于進行C4光合作用。與此同時其他研究人員正致力于分離決定C4植物異常結(jié)構(gòu)和生化特性的基因。幾年前，遺傳學(xué)家通過將玉米中的相關(guān)基因轉(zhuǎn)入水稻，從而在水稻中成功合成了C4光合作用必需酶的一種。
（4）The task, admits Robert Zeigler, IRRI's director, is daunting, and will take ten years or more. But the potential is enormous. Success would not only increase yields, but also reduce the need for water and fertilisers, since C4 plants make more efficient use of both. Other important C3 crops, such as wheat, sweet potatoes and cassava[5], could also benefit. If it all works, a second green revolution beckons.
IRRI負責(zé)人羅伯特?齊格勒承認(rèn)此項任務(wù)十分艱巨，將需要十年以上的時間才能完成，不過潛力是巨大的。由于C4植物能更為高效地利用兩種光合作用，因此研究一旦成功不但會增加水稻產(chǎn)量，而且會減少對水和肥料的需求量。其他重要的C3植物如小麥、甜薯、甜瓜等也會受益。假如一切順利，就將標(biāo)志著第二次綠色革命的到來。
[NOTES]（OXFORD）
1. paddy n. （also `paddy-field） [C] field where rice is grown 稻田. 2 [U] rice that is still growing or in the husk 稻; 稻谷.
2. cater v. 1 （a） [I, Ipr] ~ （for sth/sb） provide food and services, esp at social functions 提供飲食及服務(wù)（尤指社交方面）: cater for a party, banquet, etc 為聚會、 宴會等備辦食物 * Fifty is a lot of people to cater for! 承辦五十人的飲食可夠多的! （b） [Tn] （esp US） provide food and services for （a party, banquet, etc） 為（聚會、 宴會等）提供飲食及服務(wù). 2 [Ipr] （a） ~ for sb/sth provide what is needed or desired by sb/sth 由某人[某事物]提供、 迎合: TV must cater for many different tastes. 電視節(jié)目必須迎合各種人的愛好. （b） ~ to sth try to satisfy a particular need or demand 滿足某種需要或要求: newspapers catering to people's love of scandal 迎合人們愛看丑聞消息的報紙.
3. immersion n. [U] 1 immersing; being immersed 沉浸; 浸沉. 2 baptism by putting the whole body under water 洗禮; 浸禮. immersion heater electric heater fixed inside a hot-water tank in a home 浸入式加熱器（家庭用的）.
4. elongated adj. （made） long and thin; stretched out （被拉得）細長的; 伸長的: elongated figures in a painting 畫中的細長的人.
5. cassava n. 1 [C] tropical plant with starchy roots 木薯. 2 [U] starch or flour obtained from these roots, used to make tapioca 木薯粉.