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Isolation and characterization of abaecin, a major antibacterial response peptide in the honeybee (Apis mellifera)
P Casteels1, C Ampe, L Riviere
1Plant Genetic Systems NV, Gent, Belgium.
Abstract:
Honeybee (Apis mellifera) are frequently exposed to and likely to be infected by plant-associated bacteria. We mimicked this process by injecting bees with live bacteria and isolated five induced antibacterial substances by comparative liquid chromatographic mapping of the hemolymph. Three of these antibiotics belong to a unique family of small (18 amino acids) peptides: the apidaecins [Casteels et al. (1989) EMBO J. 8, 2387-2391]. We have now characterized a fourth bee immune response peptide. The complete sequence was established by Edman degradation of the peptide and fragments thereof. It is 34 amino acids long and contains 10 proline residues. The amino-terminal half is related to the apidaecins; similar proline motifs are also present in the amino-terminal quarter of the much longer fly diptericins. The newly identified peptide's broad spectrum, lower specific activities against Gram-negative plant pathogens and its inability to inhibit bacterial growth at medium ionic strength are different from the apidaecins. Moreover, the highest observed specific activity was against an apidaecin-resistant Xanthomonas strain. In contrast to the immediate action of apidaecins, bactericidal activity is delayed. We propose the name 'abaecin' for this new antibacterial response peptide.
Insights
Researchers discovered a new honeybee immune peptide, abaecin, which combats plant-associated bacteria. Unlike apidaecins, abaecin has delayed antibacterial activity and targets specific resistant strains.
Area of Science:
- Insect Immunology
- Antimicrobial Peptides
- Apis mellifera Biology
Background:
- Honeybees (Apis mellifera) are susceptible to plant-associated bacterial infections.
- The honeybee immune system produces antibacterial substances to combat pathogens.
- Apidaecins are a known family of small antibacterial peptides found in honeybees.
Purpose of the Study:
- To characterize a newly identified antibacterial peptide from honeybee hemolymph.
- To determine the sequence, properties, and activity spectrum of this novel peptide.
- To compare the novel peptide with existing apidaecins and diptericins.
Main Methods:
- Hemolymph analysis using comparative liquid chromatographic mapping after bacterial injection.
- Edman degradation for complete amino acid sequencing of the peptide and its fragments.
- In vitro assays to determine antibacterial activity against various bacterial strains and under different ionic conditions.
Main Results:
- A new 34-amino acid antibacterial peptide, named abaecin, was identified.
- Abaecin shares sequence similarity with apidaecins and diptericins but has distinct properties.
- Abaecin exhibits delayed bactericidal activity, a broad spectrum, and specific efficacy against apidaecin-resistant Xanthomonas strains.
Conclusions:
- Abaecin represents a novel class of honeybee immune peptides with unique characteristics.
- Its distinct activity profile suggests a complementary role to apidaecins in honeybee defense.
- Further research into abaecin could offer new insights into insect immunity and antimicrobial strategies.