Identification of ecdysone receptor (EcR) target genes in the adult brain of the European honey bee (Apis mellifera L.). Apis mellifera

Ecdysone signaling plays central roles in morphogenesis and female ovarian development in holometabolous insects. In the European honey bee (Apis mellifera L.), however, ecdysone receptor (EcR) is also expressed in the brains of adult workers, which have already undergone metamorphosis and are sterile with shrunken ovaries. Aiming at unveiling the significance of EcR signaling in the worker honey bee brain, we performed chromatin-immunoprecipitation sequencing (ChIP-seq ) of EcR to search for its target genes using 2 types of worker bee brains, younger nurse bees taking care of the brood inside the dark hives, and older foraging bees (foragers) searching for and gathering pollen and nectar outside the hives. We also conducted RNA-seq analysis to investigate the expression levels of the target genes in the brains of nurse bees and foragers before and after foraging behavior. In addition, single-cell RNA-seq analysis using forager brains (optic lobes) were performed to reveal the cell types that express EcR and its target genes.