Chennai, December 1, 2011: In honey bee workers, vitellogenin is known to influence hormone signaling, food-related behavior, immunity, stress resistance and longevity. Giving details of the research work being undertaken at the Amdam Lab, Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Dr. Gro Amdam explains: "the regulatory action of juenile hormone on vitellogenin activity is inverted in honey bees, and we have found that this vitellogenin has functions not identified in other species. First, the worker caste is charactrerized by a positive feedback loop in which vitellogenin affects the hormonal control system to suppress the systemic juvenile hormone level. Second, this vitellogenin can prolong life also as a scavenger of free radicals, thereby protecting the bee against oxidative stress damage (as established marker of aging). As vitellogenin levels primarily are functions of the bees'social roles, this relationship suggests that honey bee aging is best explained by social function rather than by chronological age."
Though it is now known that vitellogenin has remarkable effects on the social structure of the bee colony and on the logevity of the bees, little is known of the molecular mechanisms of these actions. Dr. Heli Havukainen, one of the members of Dr. Amdam's team of researchers at the University of Bergen (UiB), Norway, has been investigating the molecular structure, cleavage pattern, etc., of vitellogenin.
Researchers at the Norwegian University of Life Sciences (UMB), UiB, Norway and the Arizona State University, USA have been investigating the molecular properties of vitellogenin. Their study showed that the vitellogenin from abdominal fat body of honey bee workers contains two fragments. In a paper* published in the Journal of Experimental Biology the researchers say that their data "indicate that the honeybee fat body vitellogenin experiences cleavage unlike hemolymph vitellogenin, a pattern that can suggest a tissue-specific role."
In the following news article dated November 28, 2011, Torunn Moe of the UMB gives details of this research and the various factors of vitellogenin functioning explained by Dr. Heli Havukainen in her defense of her doctoral thesis on November 25, 2011.
*Havukainen, H., Halskau, Ø., Skjaerven, L., Smeda, B. and Amdam, G.V. 2011. Deconstructing honeybee vitellogenin: novel 40 kDa fragment assigned to its N terminus. Journal of Experimental Biology 214: 582-592.
Honey bee mystery protein is a freight train for health and lifespan
Why are bee colonies worldwide suffering mysterious deaths? A unique study describes a single bee protein that can promote bee health and solve a major economic challenge.
Honey bees are the most effective pollinators of many agricultural crops and vitally important to food production.
Honey bee health is a topic of considerable concern due to massive deaths of bee colonies in the USA and Europe. Recently, the European Union reacted by promising more resources for honey bee research, estimating European pollination to an economic value of € 22 billion.
"Detailed studies on the molecules that keep bees healthy are extremely important to the food industry as well as the global provision of food," said Dr. Heli Havukainen, who defended her PhD thesis at the Norwegian University of Life Sciences (UMB) on November 25. Her study of honey bees is a collaboration between UMB and the University of Bergen (UiB), Norway.
More protein = better health and longer life
One of these molecules is a protein called vitellogenin. "Simply put, the more vitellogenin in bees, the longer they live. Vitellogenin also guides bees to do different social tasks, such as caregiving or foraging. It also supports the immune function and is an antioxidant that promotes stress resistance. In my research, I set out to find out how this molecule is shaped and how it behaves on a nano-scale. This provides us with more knowledge about how vitellogenin is good for honey bees," Havukainen said.
Like a freight train
Under the supervision of Professor Gro Amdam (UMB and Arizona State University) and Associate Professor Øyvind Halskau (UiB), Havukainen discovered that vitellogenin can be described as a freight train consisting a locomotive and a carriage. The protein carries fat as its cargo, which it picks up in the bees' belly-fat cells - the main station. The vitellogenin "train" travels in the bee's blood and delivers the fat cargo at different local stops or stations.
"I found out that, instead of starting the train journey from the fat cell main station, some vitellogenin molecules are divided in two, so the locomotive is separated from its cargo. The cargo cannot move without a locomotive and it stays in the fat cells, while the locomotive disappears. We soon realised that this is a typical behaviour for the vitellogenin molecule," Havukainen said.
Prior to this study, scientist believed vitellogenin to be one entity, like a cargo ship, unable to separate from its cargo. Therefore, Havukainen's new discovery is a big step forward for research that aims to keep bees healthy and long lived.
"We figured out that vitellogenin can drop its fat cargo as a reaction to changing chemical conditions. How this "drop" occurs and which factor makes the locomotive move and leave its cargo are important questions in the protein world, and probably equally important to the bee," Havukainen said.
What's up with the train hitch?
The research group believes that the separation of vitellogen in two parts is a key to understanding how the protein works. They are now in search of the factor that breaks the fragile connection, or the train hitch of the protein, and lets the locomotive go.
"My discovery is that vitellogenin is not one entity. It consists of two functional parts. Now, I want to stop the separation process, so the locomotive and fat cargo are always together. This will help us figure out why the locomotive sometimes ditches its cargo and travels around on its own, and what the consequences are for the bees. This way, we can learn how vitellogenin affects social behaviour, immunity and stress resistance, and ultimately global food production and provision," Havukainen said.