Researchers at Heinrich Heine University Düsseldorf (HHU) are collaborating with colleagues from Frankfurt/Main, Oxford and Würzburg to investigate how the complex, cooperative behaviour of honey bees (Apis mellifera) is genetically programmed so that it can be passed on to subsequent generations. As they explain in the scientific journal Science Advances, they found an answer in what is known as the doublesex gene (dsx).
Behavioural 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 behaviour. In the animal kingdom, this has considerable advantages in collective foraging for food, defence against predators and the rearing of offspring.
In some animals, such as honeybees, the social behaviour bonds are so strong that the individual members form a tight-knit society that function collectively as a single “superorganism.” Through their individual behaviour, 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 that has now been published in Science Advances, emphasises: “The behavioural 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 behaviours 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 behaviour.
Sommer: “The gene programmes 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 behaviour in the hive with cameras. The resulting video sequences were analysed with the support of artificial intelligence to determine the bees’ individual behavioural patterns.
Sommer: “Our central question was whether and how the inherited behavioural 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 behaviour 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 behavioural patterns of honeybees,” explains doctoral researcher Jana Seiler, who is also a co-author of the study.
“Our findings indicate a fundamental genetic programme that determines the neuronal circuitry and behaviour of worker bees,” says Professor Dr Wolfgang Rössler from the Department of Behavioural 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 behaviour of many individuals.”