When Gregor Mendel finished his work on peas, he focused his attentions on the honey bee — the agricultural importance, social behaviour and cognitive abilities of which certainly make it a compelling genetic model. Now, honey bee genetics has taken a leap forward with the report in Nature of the Apis mellifera genome sequence by the Honey Bee Genome Sequencing Consortium.

Gazing at this AT-rich, ∼240 Mb genome, the authors have uncovered some striking genetic idiosyncrasies, which they hope will lead to the molecular mechanisms of eusociality. For example, they describe novel features of orthologues of genes that, in Drosophila melanogaster, are involved in vision, mechanotransduction, learning and memory. They also found that some gene families are much larger than their equivalents in other insects — among the most extreme of these being those that encode the royal jelly proteins, which have roles during the differentiation of social castes. Other gene families are unexpectedly small — such as those that encode detoxifying enzymes, gustatory receptors and, surprisingly, components of innate immunity — and the authors discuss how these might reflect the specialized life history of the honey bee.

Having the genome sequence has already led to the development of new tools for research into the mechanisms and origins of social behaviour. First, it has improved the annotation of ESTs, which the authors have already used to identify candidate genes that are involved in caste differentiation — their data show that changes in metabolism are important during this process. Second, by comparing European-derived and 'Africanized' honey bees (which have spread across the New World in the last 50 years), the authors identified a large array of SNPs, which will help with the cloning of genes that underlie behavioural and social traits.

These SNPs have also allowed the researchers to revise the phylogenetic and migrational history of the honey bee. Furthermore, sequence comparisons with other insects contradict the prevailing phylogeny of the Hymenoptera (ants, bees and wasps), indicating that the Hymenopteran lineage diverged earlier than previously thought, and that honey bees belong to the oldest lineage of eusocial bees.

The diversity of related papers in this month's issue of Genome Research shows how many areas of research will be accelerated by the honey bee genome sequence. Mendel — who, like subsequent geneticists, found genetic studies of this haplodiploid, polyandrous creature difficult — might have been delighted by the researchers' hope that the honey bee will help us understand the molecular basis of social life.