Apidermins (APDs) are known as structural cuticular proteins in insects, but their additional roles are poorly understood. In this study, we characterized the honeybee, Apis mellifera, APD 2 (AmAPD 2), which displays activity suggesting antimicrobial properties. In A. mellifera worker bees, the AmAPD 2 gene is transcribed in the epidermis, hypopharyngeal glands, and fat body, and induced upon microbial ingestion. Particularly in the epidermis of A. mellifera worker bees, the AmAPD 2 gene showed high expression and responded strongly to microbial challenge. Using a recombinant AmAPD 2 peptide, which was produced in baculovirus-infected insect cells, we showed that AmAPD 2 is heat-stable and binds to live bacteria and fungi as well as carbohydrates of microbial cell wall molecules. This binding action ultimately induced structural damage to microbial cell walls, which resulted in microbicidal activity. These findings demonstrate the antimicrobial role of AmAPD 2 in honeybees.

Honeybee vitellogenin (Vg) transports pathogen fragments from the gut to the hypopharyngeal glands and is also used by nurse bees to synthesize royal jelly (RJ), which serves as a vehicle for transferring pathogen fragments to the queen and young larvae. The proteomic profile of RJ from bacterial-challenged and control colonies was compared using mass spectrometry; however, the expression changes of major royal jelly proteins (MRJPs) in hypopharyngeal glands of the honeybee Apis mellifera in response to bacterial ingestion is not well-characterized. In this study, we investigated the expression patterns of Vg in the fat body and MRJPs 1–7 in the hypopharyngeal glands of nurse bees after feeding them live or heat-killed Paenibacillus larvae. The expression levels of MRJPs and defensin-1 in the hypopharyngeal glands were upregulated along with Vg in the fat body of nurse bees fed with live or heat-killed P. larvae over 12 h or 24 h. We observed that the expression patterns of MRJPs and defensin-1 in the hypopharyngeal glands and Vg in the fat body of nurse bees upon bacterial ingestion were differentially expressed depending on the bacterial status and the time since bacterial ingestion. In addition, the AMP genes had increased expression in young larvae fed heat-killed P. larvae. Thus, our findings indicate that bacterial ingestion upregulates the transcriptional expression of MRJPs in the hypopharyngeal glands as well as Vg in the fat body of A. mellifera nurse bees.

Venoms from venomous arthropods, including bees, typically induce an immediate local inflammatory response; however, how venoms acutely elicit inflammatory response and which components induce an inflammatory response remain unknown. Moreover, the presence of superoxide dismutase (SOD3) in venom and its functional link to the acute inflammatory response has not been determined to date. Here, we confirmed that SOD3 in bee venom (bvSOD3) acts as an inducer of H₂O₂ production to promote acute inflammatory responses. In mouse models, exogenous bvSOD3 rapidly induced H₂O₂ overproduction through superoxides that are endogenously produced by melittin and phospholipase A₂, which then upregulated caspase-1 activation and proinflammatory molecule secretion and promoted an acute inflammatory response. We also showed that the relatively severe noxious effect of bvSOD3 elevated a type 2 immune response and bvSOD3 immunization protected against venom-induced inflammation. Our findings provide a novel view of the mechanism underlying bee venom-induced acute inflammation and offer a new approach to therapeutic treatments for bee envenoming and bee venom preparations for venom therapy/immunotherapy.

Protein nutrition during early adulthood is closely associated with hypopharyngeal gland (HPG) development in worker honey bees, but whether peppermint oil (PO) influences this physiology and whether its effects depend on exposure route remain unclear. Newly emerged Apis mellifera workers were exposed for up to six days to dietary PO (0.05%, w/w), volatile PO (0.05% in paraffin oil, v/v), both routes, or control conditions. Protein-patty mass disappearance and recorded deaths were monitored daily, while body and head weight, HPG acinus area, feeding- and nutrient-associated gene expression in the brain and fat body, HPG mrjp1 expression, and MRJP1 protein abundance were assessed at designated sampling points. PO-exposed cages showed greater cumulative protein-patty mass disappearance and significantly altered feeding- and nutrient-associated gene expression, although individual molecular responses varied among exposure routes. All PO-treated groups had larger HPG acinus areas than controls on days 4 and 7; mrjp1 expression was significantly higher in PO-F on day 4 and in all PO-treated groups on day 7. MRJP1 protein abundance was also increased in all PO treatments. Volatile exposure showed numerically higher mortality on observation day 3, but cumulative mortality did not differ significantly from the control. These results indicate that dietary and volatile PO exposure were associated with changes in feeding-related measures and HPG development in young worker honey bees.

The complete mitochondrial genome of Bionychiurus tamilensis Thunnisa & Sumithra, 2021 was sequenced, assembled, and annotated. The mitochondrial genome of B. tamilensis is 14,937 bp in length and contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes. The overall nucleotide composition was 35.3% A, 15.8% C, 9.8% G, and 39.6% T, indicating an obvious A + T bias (74.9%). B. tamilensis was closely clustered with the following species of Onychiuridae: Allonychiurus kimi, Tetrodontophora bielanensis, Onychiurus orientalis, and Orthonychiurus folsomi.