Is complex social behavior genetically determined? Yes, as a team of biologists from Heinrich Heine University Düsseldorf (HHU) together with colleagues from Bochum and Paris discovered while studying bees. They identified a genetic factor that determines the begging behaviour of drones, which they use to obtain food socially. They are now publishing their findings in the scientific journal Nature Communications.

Male bees, or “drones”, do not have an easy time obtaining essential proteins. This is because they cannot digest pollen, the most important source of protein for bees. To avoid starvation, they depend on worker bees feeding them a pre-processed food that the workers make themselves from pollen. However, to obtain this paste, the drones must convince workers to provide the food by performing a series of behaviors.

“Such cooperative behaviour is a complex matter in the animal kingdom, as it requires close coordination between social partners. In our research, we ask ourselves what is required to orchestrate this interaction,” explains Professor Dr Martin Beye from the Institute of Evolutionary Genetics at HHU.

A research team led by Professor Beye investigated the genetic and neural basis for the cooperative behavior of bees. The biologists searched for regulators that wire the male honeybee’s brain during development in such a way that the animals display their innate social behavior for this food exchange. Researchers from Université Paris-Saclay and Ruhr University Bochum participated in the study, which has now been published in Nature Communications.

The researchers determined that the behavioral interactions necessary for food transfer can be traced back to a transcription factor called the “fruitless” or “Fru” protein. A transcription factor is a protein that can switch many other genes in the genome on and off. This factor is only active in male bees.

Using genetic technologies (CRISPR-Cas9), the researchers introduced a green fluorescent protein encoding gene into the Fru gene. This enabled them to label the cells in which the transcription factor is active.

Dr Sven Köhnen, lead author of the study: We detected it in neurons in the nervous system, which process sensory information and are used for decision-making. From this, we concluded that Fru can determine the innate behaviour of males.” Overall, Fru influences a neural network of around 1,800 neurons that is closely related to cooperative behavior.

The team then created so-called knockout mutants in which they switched off the transcription factor Fru. The researchers attached QR codes to the bodies of the mutant drones and observed their behavior using an automated camera system developed in Düsseldorf.

Köhnen: “The decision-making behavior of these bees was disrupted. They were unable to approach their conspecifics properly, begged for food less frequently and interacted in such a way that they received less food.” Co-author and doctoral student Pia Ulbricht adds: “However, other typical behaviors of the drones were not affected. Only in the context of food intake did the knockout mutants behave conspicuously.”

The mutants were also not distinct in their odor profile, as co-author Dr Thomas Eltz from Ruhr University Bochum noted. Individual odors are determined by the body’s own hydrocarbons, which are important for animal interaction. The olfactory centre, where odors are processed, was also unaffected, as research partners Professor Julie Carcaud and Professor Jean-Christophe Sandoz from Paris noted.

Professor Beye: “Our study shows that these cooperative behaviours are specified by a genetic programme that has been newly formed in the course of evolution. This programme defines the neural controls, which determine whether and for how long the behaviour sequence is executed based on perceived sensory information. Such mechanisms enable the necessary behavioural adaptations to social partners.”