Silver-spoon genes found for queen bees.

For the first time, scientists have identified some of the genes that switch on during the mysterious process that can turn genetically identical honeybees into either queens or commoners.

Just 48 hours after hatching, future queens and workers differ in the activity of seven genes, report Jay D. Evans of the Department of Agriculture's Bee Research Laboratory in Beltsville, Md., and Diana E. Wheeler of the University of Arizona in Tucson. In the May 11 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES, they describe five genes more active in workers and two genes more active in royalty.

"People think of the worker as a cutdown version of the queen," Wheeler says. "Maybe the queen is just a cutdown version of a worker."

At first, a honeybee can be whatever her sisters want her to be. For 24 hours, all hatchlings dine on royal jelly that nursemaids regurgitate. The milky slurry contains nectar, pollen, and bee secretions.

After that period, the bees that tend the youngsters sometimes single out a few for royal treatment, enlarging their cells and continuing to feed them royal jelly. These larvae grow into large adults with functional sex organs.

The nursemaids, however, leave most larvae in small cells and feed them worker jelly, a formula of nectar, pollen, and different secretions. By 48 hours after hatching, a larva can no longer switch to the royal fast track. Instead, she grows up with withered ovaries but greater visual acuity and more capacity for learning.

Earlier research showed that nursery differences affect gene activity, but scientists couldn't identify the specific genes. After Russian scientists in 1996 described an analytical technique called suppressive subtraction, "we pounced on a way that finally worked," Evans relates. He and Wheeler are the first to apply the method to honeybees.

The researchers started with larvae just 48 hours after they hatched. From future workers, Evans collected messenger RNA, molecules produced by active genes to instruct the protein-making machinery. From that RNA, he made complementary single strands of DNA.

To find worker genes, he added an identifying snippet of DNA to these DNA strands. He then flooded pools of the tagged strands with single strands of DNA made from queen messenger RNA.

At this genetic sock hop, strands from genes active only in the workers failed to find a partner from genes active in the queen. Genes that were much more active in workers than in queens left some wallflower strands, too. After several such mixings, Evans sequenced the tagged leftovers. He then repeated the process but tagged queen instead of worker DNA. Finally, he looked for resemblances between the bee genes identified and known genetic sequences.

A bee gene active in only worker larvae resembles the DNA for a fatty acid-binding protein. This strikes H. Frederik Nijhout of Duke University in Durham, N.C., as the most exciting find. He speculates that it might bind to the much-studied juvenile hormone considered key in controlling the queen-worker split.

"What the hormone is doing we have no idea," Nijhout says. Evans and Wheeler's work "gives us hope that we'll in fact find the answer, and it gives us the technique with which to do it."