Single genes control flower production.

Scientists have known that genes, including leafy (LFY) and apetala 1 (AP1), help determine the development of meristems, the tips of stems where either flowers or shoots for new leaves and stems form. Now, investigators find that LFY and AP1, each on its own, can trigger flower development.

In the Oct. 12 Nature, two teams "demonstrate for the first time that expression of single genes is sufficient to confer floral identity" on immature plant parts, George Coupland of Norwich Research Park in England asserts in an accompanying article. Once these genes have flipped the flower-development switch, many other genes get involved in producing flowers.

In mustard plants (Arabidopsis) genetically engineered so that the AP1 stays continuously active, shoots that normally produce stems and leaves form flowers instead, report M. Alejandra Mandel of the University of Arizona in Tucson and Martin F. Yanofsky of the University of California, San Diego.

The genetically altered plants flower in as little as one-third the time it takes normal plants, in part because shoots for stems and leaves form sooner than floral meristems, Yanofsky says.

Other scientists engineered Arabidopsis and an aspen tree so that the LFY gene stayed active. Those plants also flowered prematurely, report Detlef Weigel of the Salk Institute for Biological Studies in La Jolla, Calif., and Ove Nilsson of the Swedish University of Agricultural Sciences in Umea. The engineered tree produced flowers in a matter of months, whereas natural aspens take 8 to 20 years.

The findings should make breeding and genetically altering plants and trees easier, the scientists note. However, Coupland warns, transgenic plants often have an unusual form and structure that "might outweigh any advantage caused by improved flowering time."