Ever feel like your mind is not on the job? You wouldn't if you were a honey bee. A new study in today's Science shows that the active genes in their brains accurately fit their job description: either nurse or forager.
Most biologists agree that, in many animals, genes can have a strong influence on behavior. But a long-standing issue is how tight this link is: Do genes only predispose an animal for a certain kind of behavior or is their role larger? To answer this question in the humble honey bee, Charles Whitfield and colleagues at the University of Illinois, Urbana-Champaign, looked at two worker types. Young worker bees stay in the hive and look after the larvae. But when they reach the age of 3 weeks, they normally switch to foraging, commuting between the hive and far-flung flower beds. "These are really different occupations, not just passing flirtations," says entomologist and neuroscientist Gene Robinson, one of the study's authors.
From one hive, the researchers took 18 nurses and 18 foragers and screened extracts of their brains on DNA-chips, microarrays of DNA from about 5500 bee genes. Genes actively producing proteins in brain tissue constantly churn out temporary copies of themselves. By attaching fluorescent labels to these copies and then dipping the DNA-chips in this cocktail, it was possible to see exactly which genes were at work: Those positions on a chip that became fluorescent pinpointed the active genes in the bee brain.
Gene activity was quite different between nurses and foragers, with about 40% of all genes showing different activity in a nurse brain compared with a forager brain. More importantly, the patterns were very similar among individual bees doing the same chores. To test whether the difference was job-related or age-related, the scientists made a bee hive in which all workers were of the same age. This forced some workers to forage while still young, and some to continue nursing in spite of being too old. From this hive they compared 12 additional nurses with 12 foragers of the same age. Sure enough, the same differences showed up on the DNA-chips again.
The results show that the link between genes and behavior is more robust than previously thought, says Robinson. Geneticist Greg Hunt, who leads a project on bee behavior at Purdue University in West Lafayette, Indiana, says the new study is "very exciting." He adds that it will help in finding the genes that are the major switches for turning on particular kinds of behavior.