Honeybee gene specifies collective behavior, research shows

Researchers at Heinrich Heine University Düsseldorf (HHU) are collaborating with colleagues from Frankfurt/Main, Oxford and Würzburg to investigate how the complex, cooperative behavior of honeybees (Apis mellifera) is genetically programmed so that it can be passed on to subsequent generations.

As they explain in the journal Science Advances, they found an answer in what is known as the doublesex gene (dsx).

Behavioral interactions between organisms are fundamental and often inherited. Every human being and every animal interacts with other individuals in its social group in one way or another through its behavior. In the animal kingdom, this has considerable advantages in collective foraging for food, defense against predators and the rearing of offspring.

In some animals, such as honeybees, the social behavior bonds are so strong that the individual members form a tight-knit society that functions collectively as a single "superorganism." Through their individual behavior, thousands of worker bees protect the entire colony, feed it and care for the brood.

Professor Dr. Martin Beye, who heads the Institute of Evolutionary Genetics at HHU and is the corresponding author of the study, emphasizes, "The behavioral repertoire of the individual bees and their function in the colony are not learned, but rather inherited. Until now, it was not known how such complex behaviors were genetically encoded."

Together with colleagues from the universities in Frankfurt/Main, Oxford and Würzburg, the team of researchers at HHU led by Beye and first author Dr. Vivien Sommer has now discovered that a special gene known as dsx specifies worker bee-specific behavior.

The neuronal network in the bee's brain appears in green. Credit: HHU / Institute for Evolutionary Genetics

Sommer says, "The gene programs whether a worker bee takes up a task in the colony and for how long. This includes collective tasks such as caring for the larvae or foraging for food and social exchanges on food sources, for example."

The biologists used the CRISPR/Cas9 genetic scissors in their investigations to modify or switch off the dsx gene in selected bees. They attached a QR code to the manipulated bees, then monitored their behavior in the hive with cameras. The resulting video sequences were analyzed with the support of artificial intelligence to determine the bees' individual behavioral patterns.

Sommer adds, "Our central question was whether and how the inherited behavioral patterns changed as a result of the gene modification. Such changes must be reflected in the nervous system of the worker bees where the specific behavior is controlled."

The researchers introduced green fluorescent protein (GFP) into the dsx sequence so that GFP was produced together with the dsx protein. The neuronal circuits could then be viewed using fluorescence microscopy, in both the unmodified bees and in those with genetic modifications.

"We were able to use these tools to see exactly which neural pathways the dsx gene creates in the brain and how this gene in turn specifies the inherited behavioral patterns of honeybees," explains doctoral researcher Jana Seiler, who is also a co-author of the study.

"Our findings indicate a fundamental genetic program that determines the neuronal circuitry and behavior of worker bees," says Professor Dr. Wolfgang Rössler from the Department of Behavioral Physiology and Sociobiology, who led the study at the University of Würzburg.

In the next step, the researchers now want to move from the level of the individual honeybee to the bee colony superorganism.

Alina Sturm, who is also a doctoral researcher at HHU and study co-author, adds, "We hope to find the link between individual programming and the coordinated behavior of many individuals."