Brain gene expression during photoperiod-related caste determination in the primitively eusocial wasp Polistes jokahamae

Adult females of the primitively eusocial wasp Polistes jokahamae can change caste in response to photoperiod length. Short-day photoperiod females store more lipids but have less developed ovaries for hibernation (becoming gynes), whereas long-day photoperiod females have fewer lipid stores but more developed ovaries under queenless conditions (becoming egg-laying workers). To clarify the physiological mechanisms underlying photoperiod-related caste determination, comprehensive analyses of gene expression levels in the brains of short- or long-day females were performed. Short-day females showed enhanced expression of genes involved in tryptophan metabolism, insulin signaling, and nutrition, including the digestion of sugars and lipids, and production of royal jelly proteins. Long-day females showed enhanced expression of genes involved in tyramine/dopamine syntheses, epidermal growth factor receptor, insulin degradation, and oogenesis. These results suggest that photoperiod-related caste determination in P. jokahamae is controlled by common genes involved in caste determination during the preimaginal stage in other Polistes species.