Life's not fair in a beehive. Younger bees get to hang out with the honey, while older ones must fly out and forage for nectar. Now a study shows that there's a genetic difference between the cohorts: A gene controlling a bee's biological clock ramps up when it joins the daily nectar-gathering grind. The study also shows for the first time that socializing can set the pace of a biological clock.
Time means little to young bees lolling around the hive. But when bees start to forage, they must synchronize their internal clocks with the cycle of daylight and the peak nectar-producing times of flowers. So entomologist Gene Robinson and colleagues at the University of Illinois, Urbana-Champaign, suspected that the clock gene period might kick in to help as young bees matured.
The researchers searched for signs of increased gene activity when budding foragers take up their new responsibilities. They kept bees of different ages in darkness for 2 days. Then they compared levels of period mRNA, a molecule signaling that the gene is active, in the brains of the bees. Even in darkness, the older, foraging bees had twice as much period mRNA as the younger bees. Because the bees had been in a dark cage, this suggests that the gene activity does not depend on stimuli such as light or scent.
But the difference is not entirely due to aging, either. When the young bees were isolated so they could not associate with and touch older bees, the level of period mRNA ramped up twice as fast as normal.. These upstarts matured faster simply because their elders weren't around. The findings, reported in the 6 June Proceedings of the National Academy of Sciences, provide the first evidence that the period gene responds to cues from the social environment.
"The authors have done a very elegant job showing a clear connection among environmental influence, gene expression, and behavior," says Mark Winston, an entomologist at Simon Fraser University in Vancouver, Canada.