Winter is hard on plants--and on consumers who find themselves shelling out big bucks for lame legumes at the grocery store. But now researchers have tweaked the DNA of an eggplant plant so that it makes perfect fruit even during the short, and relatively chilly days of a Florida winter. Scientists say the transgenic triumph, described in the December Nature Biotechnology, could dramatically improve the quality of off-season produce.
Even in warm climates like Florida, vegetables grown in early spring can come out small or misshapen. That's because lower temperatures keep the plants from fully pollinating and fertilizing each other. Once fertilized, plants produce fruit and seeds. But a winter tomato might only have five seeds, instead of a typical 100, says Dwight Tomes, a researcher at Pioneer Hi-bred International Inc., a seed company in Johnston, Indiana. "Instead of being the size of a baseball, [a tomato] is the size of a walnut, and it's kind of hard to convince people to buy one."
Angelo Spena, a biologist at the University of Verona in Italy, with collaborators from Italy and Germany, found a way to get around the seed problem entirely by engineering plants that produced fruit, even when unfertilized. The researchers took a gene from a snapdragon plant (chosen to target the fruit-producing ovaries) and rigged it to stimulate production of a plant hormone called auxin. "Auxin triggers fruit growth," says Spena.
The researchers engineered eggplants that carried the gene and tested them alongside normal eggplants under semitropical winter conditions--7 hours of daylight at 17 degrees Celsius. The unmodified plants bore no fruit, even when pollinated by hand, but the superplants gave summer-size eggplants. Since the eggplants were unfertilized, they were also seedless. They did make seeds, however, when fertilized. Tomes thinks the technique could lead to low-cost, high-quality winter vegetables. And Spena says his group has already proved the technique on 17 different plants, including Italy's beloved vegetable, the tomato.