Transcriptomics reveals the foraging gene regulating the division of labor in Apis mellifera

Prominent traits of social insects, such as defense and foraging, are the outcomes of collective effort by many individuals. The processes that integrate worker behavior into coordinated colony patterns are not well understood. In this study, two types of division of labor (DOL) in Western honeybees (Apis mellifera) were examined: foraging (nectar, pollen, and water collection) and defense (guard bees). Methods including the proboscis extension response (PER), quantitative polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), and transcriptome analysis were employed to investigate internal regulatory mechanisms underlying these behaviors. The results showed that PER and gustatory response score (GRS) values for tasks such as water collection were significantly higher than those for defense tasks, while no difference was observed in nutritional foraging tasks like nectar and pollen collection. The relative expression levels of Amfor and PKG activity in water foragers were significantly higher than in guard bees, and pollen foragers showed higher levels than nectar foragers in nutrient collection tasks. Transcriptome analysis revealed that, compared with nectar foragers, the Amfor gene was significantly downregulated in defense and upregulated in pollen and water foragers. Compared with pollen foragers, 43 differentially expressed genes (DEGs) were identified in nectar foragers and 94 DEGs in water foragers. In contrast, 418 DEGs were found when compared with guard bees. DEGs in water foragers were related to body surface morphology, waterproof wax synthesis, and ion and water transport in the Malpighian tubules. In nectar and pollen foragers, DEGs are mainly involved in cGMP synthesis and actin binding. DEGs in defense tasks included genes related to retinol metabolism, olfaction, neurotransmitter transport, and responses to environmental changes. KEGG enrichment analysis showed that pathways regulating movement, cGMP-PKG signaling, oxidative phosphorylation, and thermogenesis, were uniquely enriched in foraging and defense tasks. Weighted Gene Co-expression Network Analysis identified that Nos (nitric oxide synthase), Camkii (calcium/calmodulin-dependent protein kinase II), and genes encoding cGMP-dependent protein kinase (PKG) were part of the cGMP-PKG pathway. These findings indicate that the foraging gene acts as a regulatory factor in the DOL in Western honeybees. Although the specific neuroethological functions of the foraging gene in the insect brain remain unclear, the PKG signaling pathway plays a storage role in neuroplasticity related to sensory, cognitive, and motor functions, forming the basis for behaviors such as foraging and aggression.