Saturday, October 28, 2006

Scientists decode honeybee genome

LOS ANGELES, Oct. 25 (Xinhua) -- The honeybee, a species that annually contributes billions of dollars to world's agricultural economy through pollination, originated in Africa and is evolving in surprising ways, a science consortium reported on Wednesday.

Honeybees, the premier pollinators on Earth, play a vital role in world's agriculture. They are also very valuable to scientists as model for allergic disease, development, gerontology, neuroscience, social behavior and venom toxicology.

A genome analysis of the honeybee, or Apis mellifera, has yielded new information about the origins and spread of honeybees throughout Europe, Asia, and North and South America, the scientists said in the journals Nature and Science.

The job of mapping the insect's genome enlisted 112 researchers at 63 different institutions that built up the International Honeybee Genome Consortium. About 10,000 genes were found, 30 percent less than the fruit fly or mosquito, the scientists said.

To sequence a genome, scientists first extract the DNA and break it into tiny pieces. Each of those pieces of genetic material is then sequenced. Lastly, an elaborate computational process puts the pieces back together in correct order.

The genus Apis is composed of 10 species, nine of which are confined to Asia. The one exception, A. mellifera, is distributed from sub-Saharan Africa to Central Asia to Northern Europe, and has more than two dozens distinct geographical subspecies, the scientists found.

"Our analysis indicates that the honeybee, Apis mellifera, originated in Africa and spread into Europe by at least two ancient migrations," said Charles Whitfield, a professor of entomology at the University of Illinois at Urbana-Champaign who led the study.

"The migrations resulted in two European populations that are geographically close, but genetically quite different," Whitfield said. "In fact, the two European populations are more related to honey bees in Africa than to each other."

The first findings appearing in major scientific journals include:

--The honeybee originated in Africa and spread into Europe by at least two ancient migrations. In the New World, introductions of the western and northern European subspecies began in North America as early as 1622.

--Honeybees have many more genes related to smell, compared with fruit flies or mosquitoes, but far fewer genes related to taste.

The enhanced number of odorant receptors underlies the honeybee's remarkable olfactory abilities, including perception of pheromones, kin recognition signals, and social communication within the hive. A large number of odorant receptors also allow the bees to find food and communicate the location of it to other bees.

--Scientists found clues for social cues, a form of bee pressure that can cause nurse bees to become foragers in response to needs of the hive. The job shift involves changes in thousands of genes in the honeybee brain: some genes turn on, while others turn off.

A few "master regulator" genes known to function in the development of fruit flies have been implicated in regulating the activity of these thousands of genes. It appears that master regulator genes involved in nervous-system development in fruit flies are re-used by nature for behavioral functions in adult honeybees.

The findings could have significant implications for honeybee breeding and the crucial role these creatures play in farming worldwide, according to the scientists.

Robbing the Bees: A Biography of Honey--The Sweet Liquid Gold that Seduced the World