As home gardeners in the US page through seed catalogs (目录册) and pick out their favorite plants this week, there's a new seed that has never been available to them before: a purple tomato. It is the first genetically engineered food crop to be directly marketed to home gardeners and the seeds went on sale Saturday.
The lending scientist behind the tomato is Cathie Martin. About 20 years ago, she set out to create a transgenic (转基因的) tomato, using DNA from a purple snapdragon, which is an unrelated eatable flower. Her goal was to develop a tomato with high levels of anthocyanins, chemicals that give blueberries, blackberries, eggplant and purple cabbage their color. Research has shown that anthocyanins also have anti-cancer and anti-aging effects.
"It's normal for tomatoes to make these healthy chemicals. But they typically don't make them very much in the fruit," Martin told reporters in an interview. "They normally appear in the leaves and stems."
So she started with, separating the DNA in the snapdragon flower that turns on and off the purple color. Next, she used a basic technique that was figured out by scientists in the 1980s to introduce it into a certain bacteria so that the tomato could then take in the foreign genetic material and express this new gene.
The result? In a paper published in Nature, Martin found that the purple tomato had, per weight, as much anthocyanin as a blueberry or eggplant, and that the mice who ate a diet mixed with purple tomatoes lived 30% longer than those who didn't.
"Americans eat more tomatoes annually, so it makes the nutritional benefits more accessible," Martin said.
Of course, some people have raised health concerns about eating genetically engineered foods. But these foods were introduced three decades ago and studies have not shown any harm.
"The purple potato is another great example of how the outcomes and applications of such biotechnologies can improve our life," Martin said.
