The approach could help vegetarians get all the nutrients they need in new ways.

这一方法可以帮助素食者通过新途径获取所需的所有营养。

Veggies pack lots of nutrients. But our bodies need some nutrients that can be found only in animal products， such as meat and milk. Now， researchers have tweaked1 the genes in leaves so that plants， too， can at last make some of these compounds. This might one day let vegetarians and vegans rely on plants for the full range of nutrients their bodies need.

蔬菜富含多种营养，但人体所需的某些营养素只能从肉类、牛奶等动物产品中获取。如今，研究人员通过微调植物叶片的基因，使植物最终也能合成部分动物源性营养素。未来，素食主义者和纯素食者或许可以依靠植物获取身体所需的全部营养。

“My mom is a vegetarian，” says Pengxiang Fan. “So I started looking at what I can do to improve the plant-based diet.” A biochemist， Fan works at Zhejiang University in Hangzhou， China.

“我妈妈是素食主义者，”范鹏祥说，“所以我开始研究如何改善植物性饮食。”范鹏祥是一位生物化学家，在中国杭州的浙江大学工作。

Enzymes are proteins that speed up chemical reactions inside living things. To pump out2 the animal-type nutrients， plant leaves need enzymes they don’t normally have. In this case， they need enzymes that help turn certain amino acids—the building blocks of proteins—into compounds normally found only in meat.

酶是能够加速生物体内化学反应的蛋白质。为了合成动物源性营养素，植物叶片需要它们通常不具备的酶。具体来说，它们所需的那类酶能够将某些氨基酸（蛋白质的组成单位）转化为通常只存在于肉类中的化合物。

Fan is part of a team that put genetic instructions for making these animal-based enzymes into a bacterium： Agrobacterium tumefaciens. This microbe can then transfer genes to plants.

范鹏祥研究团队将制造这些动物源性酶的基因指令植入了根癌农杆菌。接下来，这种微生物便可将基因转移到植物中。

The team prepared multiple sets of genetic instructions. The sets differ in which amino acids and nutrients they can make. By combining the sets in different ways—like combining Lego blocks to build different structures—the instructions would allow plants to make different nutrients. The researchers then injected bacteria carrying these instructions into the leaves on a relative of the tobacco plant.

研究团队准备了多组基因指令，这几组指令能够合成不同的氨基酸和营养素。通过不同的组合方式——就像用乐高积木搭建不同结构一样——这些指令可以让植物合成不同的营养素。研究人员随后将携带这些指令的细菌注入一种烟草近亲的叶片。

The treated leaves then made two animal-type nutrients. One was creatine. It’s a molecule formed from three amino acids. The other， carnosine， is made from two amino acids. In both people and animals， creatine helps bring energy to muscles. Carnosine is an antioxidant. It also helps stave off3 muscle fatigue.

经过处理的叶片合成了两种动物源性营养素：一种是肌酸，由三种氨基酸组成；另一种是肌肽，由两种氨基酸组成。在人和动物体内，肌酸有助于为肌肉提供能量，而肌肽是一种抗氧化剂，还能帮助延缓肌肉疲劳。

Which nutrient the leaves made depended on which genetic instructions they had received. After four to five days， the researchers harvested leaves from the plants.

叶片合成出哪种营养素取决于它们接收到的基因指令。……