Date Published:

JUN

Abstract:

Small cysteine-rich peptides have diverse functions in insects including antimicrobial defense, phenoloxidase activity regulation, and toxic inhibition of ion channels of prey or predator. We combined bioinformatics and measurements of transcript abundance to start characterizing AmOCLP1, a recently discovered Inhibitor Cysteine Knot peptide in the honey bee Apis mellifera. We found that the genomes of ants, bees, and the wasp Nasonia vitripennis encode orthologous sequences indicating that OCLP1 is a conserved peptide and not unique to the honey bee. Search of available EST libraries and quantitative real time PCR analyses indicate that the transcript of AmOCLP1 is ubiquitous with expression in life stages ranging from embryos to adults and in all tested tissues. In worker honey bees AmOCLP1 expression was not associated with age or task and did not show clear enrichment in any of the tested tissues. There was however a consistent trend toward higher transcript levels in the abdomen of foragers relative to levels in the head or thorax, and compared to levels in the abdomen of younger worker bees. By contrast, in drones AmOCLP1 transcript levels appeared higher in the head relative to the abdomen. Finer analyses of the head and abdomen indicated that the AmOCLP1 transcript is not enriched in the stinger and the associated venom sac or in cephalic exocrine glands. The evolutionary conservation in the Hymenoptera, the ubiquitous expression, and the lack of enrichment in the venom gland, stinger, exocrine glands, and the brain are not consistent with the hypotheses that OCLP1 is a secreted honeybee toxin or an endotoxin acting in the central nervous system. Rather we hypothesize that OCLP1 is a conserved antimicrobial or phenoloxidase inhibitor peptide. (C) 2014 Elsevier Ltd. All rights reserved.