Biologists Identify Honeybee 'Clean' Genes Known For Improving Survival

PHYS.org York University February 15, 2019

Credit: CC0 Public Domain

Credit: CC0 Public Domain

The key to breeding disease-resistant honeybees could lie in a group of genes—known for controlling hygienic behaviour—that enable colonies to limit the spread of harmful mites and bacteria, according to genomics research conducted at York University.

Some worker honeybees detect and remove sick and dead larvae and pupae from their colonies. This hygienic behaviour, which has a strong genetic component, is known to improve the colony's chance of survival. The researchers narrowed in on the "clean" genes that influence this behaviour to understand the evolution of this unique trait.

The finding, published today in the journal Genome Biology and Evolution, could lead to a new technique for use in selective breeding programs around the world to enhance the health of honeybees.

"Social immunity is a really important trait that beekeepers try to select in order to breed healthier colonies," said Professor Amro Zayed, a bee genomics expert in the Department of Biology, Faculty of Science. "Instead of spending a lot of time in the field measuring the hygienic behaviour of colonies, we can now try breeding bees with these genetic mutations that predict hygienic behaviour."

Statistics Canada estimates that honeybee pollination contributes between $3.15 to $4.39 billion per year to the Canadian economy including some of Canada's most lucrative crops like apples, blueberries and canola. In Canada, and around the world, beekeepers have experienced higher than normal colony losses. Last winter, Canadian beekeepers lost up to 33 per cent of their colonies.

"This study opens the door to using genomics to breed healthier and disease-resistant colonies that have higher social immunity," explained Zayed. "This is of huge importance to the greater community of geneticists who are interested in understanding the genetics of this novel trait."

Zayed worked on the study with 13 bee biologists from York University, University of British Columbia, University of Manitoba, and Agriculture and Agri-Food Canada.

In the study, the biologists sequenced the genomes of three honeybee populations; two of them bred to express highly hygienic behaviour and a third population with typical hygiene. Brock Harpur, Zayed's former doctoral student who is now an assistant professor at Purdue University's Department of Entomology, examined the genomes of bees from each of these three populations and looked for areas that differ between the unhygienic and hygienic bees. Harpur pinpointed at least 73 genes that likely control this hygienic trait.

"Now that we have identified these candidate genes, we can look for the mechanisms of hygienic behavior and begin to develop tools for beekeepers to breed healthier colonies," explained Harpur.

The biologists are planning to pilot a marker-assisted breeding program for hygienic behaviour, in which bees are selected for breeding based solely on their genetic information.

"We think there is a lot of potential here of breeding disease-resistant colonies with a simple genetic test," said Zayed.

Explore further: New genetic test will improve biosecurity of honey bees around the globe

More information: Brock A Harpur et al, Integrative Genomics Reveals the Genetics and Evolution of the Honey Bee's Social Immune System, Genome Biology and Evolution (2019). DOI: 10.1093/gbe/evz018

Provided by: York University

https://phys.org/news/2019-02-biologists-honeybee-genes-survival.html#jCp

Evolution of Bee Behavior: York University Research

TORONTO– Worker bees have become a highly skilled and specialized work force because the genes that determine their behaviour are shuffled frequently, helping natural selection to build a better bee, research from York University suggests.

The embargoed study, to be published October 15 at 3pm EST in PNAS (Proceedings of the National Academy of Sciences), sheds light on how worker bees – who are sterile – evolved charismatic and cooperative behaviours such as nursing young bees, collecting food for the colony, defending it against intruders, and dancing to communicate the location of profitable flowers to nestmates.

When York University researchers examined the honey bee genome, they discovered that the genes associated with worker behaviour were found in areas of the genome that have the highest rate of recombination. Recombination represents a shuffling of the genetic deck: recombination in the ovaries of a queen shuffles the chromosomes she inherited from her parents. As a result, the queen's female offspring are likely to inherit mosaic chromosomes with different combinations of mutations, says Biology Professor Amro Zayed, whose lab conducted the research. 

Recombination allows natural selection to act on specific mutations without regard to neighbouring mutations.

"If I'm a good rower in a dragon boat with 49 poor rowers, I am going to lose all of my races. But if teams were shuffled after every race, I'll likely have a better chance of winning. I may even get to be in a boat with 49 good rowers just like myself," says Zayed. "The same thing happens with mutations on a chromosome. Recombination makes the evolutionary fate of mutations independent of their surrounding neighbours, which enhances the process of natural selection.".

The team believes that they have solved one of the mysteries of the honey bee's genome, says postdoctoral research associate Clement Kent, lead author on the study.

"The honey bee has the highest rates of recombination in animals – ten times higher than humans. Our study shows that this high degree of genetic shuffling has turned on the evolutionary faucet in parts of the bee genome responsible for orchestrating worker behaviour," says Kent. "This can allow natural selection to increase the fitness of honey bee colonies, which live or die based on how well their workers 'behave'."

Subscribe to the American Bee Journal and sign up for ABJ Extra