The molecular basis of sex determination in honeybees

In 1845 Dzierzon uncovered that parthenogenesis in honeybees (Apis mellifera) is a mechanism to determine male and female sexes. This was the first rigorous report of a sex determination mechanism that also explained the strong female sex ratio in honeybee colonies in which most colony members are sterile females (workers). More than 170 years later we have uncovered that the genotype of complementary sex determiner (csd) gene controls the sexual fate in honeybees. Heterozygosity at csd determines femaleness, while homo- or hemizygosity induces maleness. In local populations, more than 15 alleles segregate and at the amino acid level, alleles in heterozygous individuals differ from 10 to 25%. However, how the amino acids differences regulate a reliable binary sex determination signal is unknown. I will present our results on the molecular decision process which we gained from our evolutionary, genetic and biochemical studies.