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Honeybee genome creates buzz about social behavior

Decoding the species' DNA may shed light on human biology.

October 26, 2006|Karen Kaplan | Times Staff Writer

Scientists have decoded the DNA of the Western honeybee, a feat that researchers say could help illuminate the genetic underpinnings of social behavior.

An international team of nearly 200 scientists reported today that they had identified 10,157 genes. That's fewer than those in the genomes of the fruit fly, mosquito or silkworm, but sufficient to produce the only non-primate species that communicates through a symbolic language.

The genome of Apis mellifera was published in the journal Nature, along with a series of accompanying articles in Science, Proceedings of the National Academy of Sciences and other scholarly journals.

"Honeybees are important models to study the regulation and evolution of life in a society, especially social behavior itself," said team co-leader Gene Robinson, director of the neuroscience program at the University of Illinois at Urbana-Champaign.

"We hope to extrapolate the biology to humans," added Saurabh Sinha, a computer science professor at Urbana-Champaign who led one of the companion studies about genes involved in social behavior.

A typical honeybee begins its career in the hive, caring for eggs and larvae. After about two or three weeks, environmental cues from the colony turn on thousands of dormant brain genes and silence thousands of others. That prompts the bee to leave the nest in search of nectar and pollen, the researchers reported.

When a new food source is discovered, returning bees perform a "waggle dance" to tell other hive members how to find it. If more foragers are needed, bees execute a "shaking dance," and if they need to recruit more food handlers, they initiate a "tremble dance."

Honeybees use pheromones to keep track of the social standing of fellow colony members and differentiate between kin and outsiders. Compared with other insects, the researchers found, honeybees have more genes devoted to sensing smells. But they have fewer genes for taste, perhaps because they tend to eat where other bees ate and therefore don't need as much sensitivity for detecting poisons, scientists theorized.

The researchers were surprised to find that honeybees had relatively few genes for regulating immunity despite living in cramped quarters where disease might easily spread. Perhaps the bee society works to minimize incursions from parasites and pathogens, possibly by having members groom one another, Robinson said.

The researchers also discovered that many bee genes had more in common with humans than with fruit flies, such as genes involved in regulating circadian rhythms and the chemical method used to regulate gene expression.

By analyzing 1,136 genetic markers that varied among 341 honeybees, scientists concluded that the species originated in Africa -- not Asia, as originally thought -- and spread to Europe and Asia in two distinct ancient migrations. They were brought to the New World by European explorers beginning in 1622.

The subspecies known as the "killer" bee was imported to Brazil in 1956 to boost honey production and has spread throughout the Americas, displacing their European counterparts.

Scientists use honeybees to study human health, including immunity, allergic reaction, antibiotic resistance, development, mental health, social behavior and longevity. Bees also pollinate billions of dollars' worth of crops each year.

Sequencing of the honeybee began in early 2003 at the Human Genome Sequencing Center at Baylor College of Medicine in Houston and lasted about a year. Researchers wound up with about 260 million DNA base pairs. Though less than one-tenth the size of the human genome, the honeybee genome contains roughly half as many genes, the researchers reported.

The project was funded with $6.9 million from the National Human Genome Research Institute, part of the National Institutes of Health, and $750,000 from the U.S. Department of Agriculture.

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karen.kaplan@latimes.com

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