Mark Vaeck

Apidaecins : antibacterial peptides from honeybees

Although insects lack the basic entities of the vertebrate immune system, such as lymphocytes and immunoglobulins, they have developed alternative defence mechanisms against infections. Different types of peptide factors, exhibiting bactericidal activity, have been detected in some insect species. These humoral factors are induced upon infection. The present report describes the discovery of the apidaecins, isolated from lymph fluid of the honeybee (Apis mellifera). The apidaecins represent a new family of inducible peptide antibiotics with the following basic structure: GNNRP(V/I)YIPQPRPPHPR(L/I). These heat‐stable, non‐helical peptides are active against a wide range of plant‐associated bacteria and some human pathogens, through a bacteriostatic rather than a lytic process. Chemically synthesized apidaecins display the same bactericidal activity as their natural counterparts. While only active antibacterial peptides are detectable in adult honeybee lymph, bee larvae contain considerable amounts of inactive precursor molecules.

Fusion proteins with both insecticidal and neomycin phosphotransferase II activity

Hybrid proteins consisting of N‐terminal fragments of increasing length of a Bacillus thuringiensis insecticidal protein (Bt2) fused to neomycin phosphotransferase II (NPTII) were produced in Escherichia coli. The minimum fragment required for insect toxicity is comprised of the first 607 amino acids of Bt2. Fusion proteins not containing this minimum fragment were non‐toxic. The NPTII activity of the different non‐toxic hybrid proteins varied considerably but was not correlated with the length of the Bt2 fragment. Fusion proteins including the minimum toxic fragment of Bt2 exhibited insecticidal and NPTII activity comparable to that of the individual proteins. This was largely independent of the fusion point within Bt2. Our data suggest that the conformation of the Bt2 polypeptide exerts an important influence on the enzymatic activity of the fused NPTII protein. The combination of insecticidal activity and a dominant selectable trait into one protein offers important advantages for the generation of insect resistant transgenic plants.