Plants can grow flower petals all over if given the right encouragement, according to two new studies. By permanently turning on the genetic program that controls petal development, researchers grew mustard plants that had petals where leaves would normally sprout. The finding will help researchers figure out the sequence of commands that causes flowers to mature.
This isn't the first such trick. In the late 1980s, scientists working with Arabidopsis, the lab rat of the plant kingdom, convinced the plant to grow leaves instead of the various parts of a flower--petals, sepals, stamens, and pistils. They did this by removing just three genes, named A, B and C. But researchers couldn't make flower parts grow where leaves should be.
Recently researchers reported that another set of genes, dubbed SEPALLATA 1, 2 and 3, controlled the operation of genes B and C. Suspecting that SEPALLATA genes might direct flower development, two teams permanently turned on the SEPALLATA genes in Arabidopsis. The resulting plants had white, petallike structures where leaves should be, although none of the other flower parts were present. Scanning electron micrographs showed that the misplaced organs had petal cells rather than the types of cells found in leaves. Developmental biologist Martin Yanofsky of the University of California, San Diego, says, "now we know we have all the players in the game--the master regulators of organ identity in flowers." Yanofsky and colleagues report the findings in the 6 February 2001 issue of Current Biology.
The same conclusion was published in the 25 January 2001 issue of Nature by Takashi Honma and Koji Goto of Japan's Kyoto University. The Japanese team went one step further, Yanofsky says, by showing that the SEPALLATA protein interacts physically with the B and C proteins.
The story has delighted other researchers. "I'm surprised it's this simple--and it's a neat experiment because it's so definitive," says Elliot Meyerowitz, a plant developmental geneticist at the California Institute of Technology in Pasadena. Karl Niklas, a plant evolutionary morphologist at Cornell University in Ithaca, New York, says that knowing what genes control the growth of plant organs will help researchers get at the heart of developmental processes.
The Yanofsky lab