No abstract

-The inhibition bands showing activity against Gram-positive bacteria were detected by analyses of acidic extracts of honeybee heads, thoraxes, and royal jellies (RJs) using a bacterial growth-inhibition assay on polyacrylamide gel. The presence of antibacterial peptide royalisin and another unknown peptide was found in two detected RJ inhibition bands by N-terminal sequencing. The data suggested that royalisin was the peptide responsible for the activity against Paenibacillus larvae larvae and other tested Gram-positive bacteria. The analyses of RJs collected from individual colonies at two apiaries, one of which showed incidence of American foulbrood, revealed differences in the content of the antibacterial peptide. The results suggest that the differences might be associated with genetic variability between colonies.Apis mellifera / royal jelly / Paenibacillus larvae larvae / American foulbrood / antibacterial peptide

Honeybee brood food, larval jelly (LJ) contains antimicrobial peptide defensin1 that is able to inhibit in vitro growth of the pathogen causing American foulbrood (AFB). This fact suggests that LJ defensin1 could participate in defense of colonies against AFB. We assume that the potential defense function of defensin1 in vivo might depend on its amount in LJs. Therefore, we investigated the expression of defensin1 in colonies. The expression was examined on protein and mRNA levels in colonies of several Apis mellifera carnica lines collected in 3 apiaries (1 infected with AFB) with the aim to identify factors influencing the expression. Levels of defensin1 were determined in royal and worker jellies by a developed immunoblot procedure employing antibodies generated against the recombinant peptide. Defensin1 mRNA levels in nurse heads were explored by dot blot hybridization using transcript of two MRJP genes for normalization. Analyzed LJs contained various amounts of defensin1 (0.159-0.524 µg/mg jelly). Higher variations in defensin1 levels were observed among LJ samples collected from different colonies than among those collected within single colony. Colonies producing LJs with elevated defensin1 levels occurred among various honeybee lines. Levels of defensin1 mRNA varied in heads of nurses and the variations correlated with defensin1 peptide levels in LJs only in some colonies. Obtained data demonstrate that defensin1 is constitutively expressed into LJs in colonies and indicate that its levels in jellies are determined by genetic factors regulating transcription and/or translation/posttranslation processes in nurses. AFB infection, larval age and type of LJ do not seem to affect the levels of the peptide in LJs. Findings made in this work suggest that it should be possible to breed novel honeybee lines expressing higher amounts of defensin1 into LJs.