Ingredients trigger insects' genes for detoxification and immune defenses
Honey is more than a sweet treat to bees. It turns out that it doses honeybees with certain compounds that switch on their detox defenses.
Instead of relying on their own honey for food during the winter, today’s commercially kept honeybees often get fed sugar substitutes and protein supplements. The sugar sources such as high-fructose corn syrup may be missing something helpful, however. New tests find compounds in honey that trigger surges of activity in genes needed for detoxifying chemicals or for making antimicrobial agents, researchers report April 29 in the Proceedings of the National Academy of Sciences.
Undisturbed by beekeepers, adult bees would sip flower nectar to keep themselves going and collect pollen to squish into a softened paste to feed to their young. They make honey from extra nectar and store it to eat during tough times without fresh flowers.
In that honey, the most effective trigger for detox genes is p-coumaric acid, report entomologist May Berenbaum and her colleagues at the University of Illinois at Urbana-Champaign. It’s a building block of the coatings for pollen grains.
Honeybees these days have plenty to detoxify; 121 pesticides and their breakdown products showed up in a 2010 survey of honeybees and their hives in 23 states and one Canadian province.
Relentless exposure to pesticides on crops and to antimite treatment in their own hives ranks among the major suspects contributing to bees’ precarious health in the United States. Winter losses have been large in recent years, including those from colony collapse disorder, the puzzling disappearance of worker bees.
Knowing that honey’s p-coumaric acid activates detox genes, Berenbaum says, “it might be helpful to reexamine the adequacy of the artificial bee diets.” Some of these honey substitutes went into use decades ago when bees didn’t face the challenges they do today.
The connection between pollen and enhanced defenses fits with what bee specialists have noticed in the field, says Dennis vanEngelsdorp of the University of Maryland in College Park. When rain or drought shrinks bees’ pollen haul in the fall, colonies don’t survive as well during the winter.
Studies have shown that pollen from diverse flowers makes for a better diet for bees than the artificial diets people provide, says Jeff Pettis of the U.S. Department of Agriculture’s Bee Research Laboratory in Beltsville, Md. Says Pettis, who was not involved in the new study: “We need better forage opportunities for all pollinators.”
Scientists are just learning about the honeybees’ detox system. The honeybee has only about a third to half as many detox genes as many other insects do. That puzzles Berenbaum since honeybees collect pollen and nectar from plants throughout the year, exposing them to many different compounds.
Also, work now shows that honeybee detox genes may not follow the usual pattern of turning on when something to detoxify appears, Berenbaum says. Exposing bees to a drug compound in a standard lab test had no effect. Instead, the big cue for the genes may be the pollen compound. It’s not a bad choice, she says, since it’s in everything they would naturally eat.
Berenbaum warns against premature bee dosing from these initial results. “I do want to make sure that beekeepers don’t immediately run out and start mixing p-coumaric acid with their high-fructose corn syrup,” she says. At this early stage, she doesn’t know whether giving the bees the wrong dose could actually harm them.
W. Mao, M.A. Schuler and M.R. Berenbaum. Honey constituents up-regulate detoxification and immunity genes in the western honey bee Apis mellifera. Proceedings of the National Academy of Sciences. Posted April 29, 2013. doi: 10.1073/pnas.1303884110. [Go to]
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