January 30, 2014
Ultrabithorax Gene Creates Differences In Honey Bee Queens And Workers
April Flowers for redOrbit.com - Your Universe Online
In a hive of honey bees, the jobs of queen and worker are drastically different. A new study from Michigan State University and Wayne State University reveals, however, that only a single gene separates the two. The findings, published in Biology Letters, show this gene not only determines leg and wing development, but it also plays a crucial role in the evolution of bees' ability to carry pollen.
“This gene is critical in making the hind legs of workers distinct so they have the physical features necessary to carry pollen,” said Zachary Huang, MSU entomologist. “Other studies have shed some light on this gene’s role in this realm, but our team examined in great detail how the modifications take place.”
The gene is called Ultrabithorax, or Ubx, and it allows workers to develop a smooth spot on the hind legs where the pollen baskets are located. The gene also promotes the formation of 11 neatly spaced bristles on another part of the legs. This section is known as the "pollen comb."
Another part of the hind legs affected by the Ubx gene is known as the pollen press. It is a protrusion that helps pack and transport pollen back to the hive.
Ubx promotes the development of these features on worker bees, but not on the queens. The team confirmed this by isolating and silencing Ubx — which made the pollen baskets, specialized leg features used to collect and transport pollen, disappear completely. The team also saw an inhibition of the growth of pollen combs, as well as a reduction in the size of pollen presses.
Bumble bees are in the same family as honey bees, but there are differences. Bumble bee queens, for example, have pollen baskets similar to workers. In bumble bees, Ubx played a similar role in modifying hind legs because the gene is more highly expressed in hind legs than it is in front and mid legs.
There are more than 300 species of bees, other than the honey bee, in Michigan alone — including solitary leaf cutter bees, communal sweat bees and social bumble bees.
“The pollen baskets are much less elaborate or completely absent in bees that are less socially complex,” Huang said. “We conclude that the evolution of pollen baskets is a major innovation among social insects and is tied directly to more-complex social behaviors.”
Huang and his team plan future research to investigate how bees could be improved to become better pollinators. They concede that this won't provide a solution to bee colony collapse disorder, however, it could provide an option for improving the shrinking population of bees' capacity for pollen collection.