Researchers from Halle discover genetic basis for social behaviour in bees

In the study, scientists from Europe, Asia and the Americas compared the genomes of ten species of bees that exhibit different degrees of social behaviour. “While several wild bees live their entire lives as solitary insects, other bees live in colonies with highly complex social structures, allowing for efficient division of labour,” explains Professor Robin Moritz from the Institute of Biology at MLU.

The University of Illinois at Urbana-Champaign spearheaded the study in which numerous international research institutions including MLU also participated. The study's findings were published on Thursday evening in “Science”. In the study, the scientists used five bee genomes that had already been sequenced, as well as the newly-sequenced genomes of five additional species of bees.

The researchers were astonished to find that the same genes aren't always active in complex social organisations. “There is no single gene that makes a bee social,” says Moritz, summing up the study. Instead there are patterns in the regulatory networks that are responsible for the activity of different genes. These networks represent cascades of multiple genes that are switched on or off together: the more complex the bees' social organisation is, the larger is the network of the collectively regulated genes.

The researchers also discovered that, as the degree of social organisation increases, so too does the number of so-called transcription factor binding sites. These binding sites serve as the critical on and off switches for regulating complex gene cascades. Similarly, the methylation of genes also increases with increasing complexity of the social organisation as an additional mechanism to control whether a gene is activated or not.

In their work on the project, Robin Moritz's team of biologists in Halle examined the different bee genomes for so-called “jumping genes”. “These DNA segments change position within the genome, in other words, jump to other genes and are able to deactivate them,” explains Dr Michael Lattorff, who works at the Institute of Biology alongside Moritz.

The researchers found less of these elements in the socially complex bee species. It has yet to be conclusively determined whether this is the reason for their complex social organisation, or a result of it. Professor Martin Hasselmann from the University of Hohenheim and an alumnus of MLU was also a member of the international team. He and his team mainly looked at the genes involved in determining the gender of bees.

The research group led by Robin Moritz, Michael Lattorff and Martin Hasselmann also participated in other publications that appeared in the scientific journal “Genome Biology”. In these studies they examined the genome and sequenced the DNA of the buff-tailed bumblebee (Bombus terrestris) and the common eastern bumblebee (Bombus impatiens), a native of North America. In one publication the researchers compared the DNA of both bumblebees to that of the closely related honeybee. Their other publication analysed the immune system of bumblebees and the genetic basis for their social behaviour.

Publications:

Kapheim et al. 2015. Genomic Signatures of Evolutionary Transitions from Solitary to Group Living. Science, 14.05.2015; DOI: 10.1126/science.aaa4788

Sadd et al. 2015. The genomes of two key bumblebee species with primitive eusocial organization, Genome Biology, dx.doi.org/10.1186/s13059-015-0623-3

Barribeau et al. 2015. A depauperate immune repertoire precedes evolution of sociality in bees, Genome Biology, dx.doi.org/10.1186/s13059-015-0628-y