This is a desirable trait in many crops, such as wheat and rice, because it allows the plant to put more energy into the grain instead of stalks, and it reduces the chance that plants will topple and be damaged by wind and rain. Last year, Harberd's group identified an Arabidopsis gene called gai as that plant's equivalent of one of the mutant genes that causes dwarfing in both rice and wheat. The genes apparently code for a protein in the signaling system through which the hormone giberellin stimulates plant growth. Previous efforts to breed dwarf basmati rice failed, Harberd notes, because the crosses exchanged thousands of rice genes along with the dwarfing character, and breeders ended up with short plants whose rice had lost its fine taste. But by shooting the mutant Arabidopsis gene into cultured basmati rice cells and then regenerating them into whole plants, Harberd's team has produced short plants that retain their tasty grains.
Plants shaded by their neighbors often bolt upward to reach sunlight.
Researchers, including Quail, are focusing on pigment-containing proteins called phytochromes that help a plant tell when it's in the shade. Sunlight filtered or reflected by leaves has more light at the far red end of the spectrum than clear sunlight does, and certain phytochromes can detect that difference and pass the information on to nuclear genes involved in growth control. Suppressing phytochrome B activity could therefore make plants less responsive to far red light, which should reduce the tendency to bolt. The strategy is now being tested with potatoes. In addition to suppressing unwanted vertical growth, plant genetic engineers are trying to encourage growth in other directions.