Characterization of antimicrobial peptide genes from Japanese honeybee Apis cerana japonica (Hymenoptera: Apidae)

Two antimicrobial peptide cDNA clones, abaecin (named AcjAba) and defensin (named AcjDef2) were isolated from the Japanese honeybee, Apis cerana japonica, using rapid amplification of cDNA end (RACE) methods. Deduced amino acid sequences of AcjAba and AcjDef2 in A. c. japonica showed high identity with those in the European honeybee, Apis mellifera (97.1%, and 93.0%, respectively). In the mature peptide region, only one amino acid residue (Val) of A. mellifera abaecin was replaced with (Ile) of A. c. japonica abaecin. Quantitative real-time RT-PCR was carried out to investigate the expression profiles of AcjAba and AcjDef2 after inoculation with Paenibacillus larvae, the causative agent of American foulbrood. The transcription of AcjAba and AcjDef2 was not significantly up-regulated in response to exposure to P larvae. As social insects, honeybees have evolved behavioral traits during their evolutionary history to reduce threats from invading pathogens. The relationship between the defensive behaviors and innate immune systems of Japanese honeybees is discussed.