The role of catecholamine-b-alanyl-ligase in the innate immune response of insects

JULIETA SCHACHTER, MARTÍN M. PÉREZ, LUIS A. QUESADA-ALLUÉ

Roscoff, Francia

Congreso; Conferences Jaques Monod. Insect immunity: the post genomic era. La reponse immunitaire des Insectes: l'ere post-genomic; 2006

Insects trigger a multifacetic innate immune response to fight microbial infections. Antimicrobial peptides are the main substances involved in the rapid humoral reaction. We show that septic injures also induce, in two holometabolous insects (Tenebrio molitor and Ceratitis capitata), the synthesis of N-b-alanyldopamine (NBAD), which is known as the main sclerotization precursor of insect brown cuticles. We demonstrated in cell-free extracts that NBAD synthase is induced in the epidermis and exhibit the same properties of the ecdysone-induced enzyme expressed only at the time of cuticIe molt. In the Medfly (C. capitata) this cathecolamine-b-alanyl-ligase is coded by the gene niger and the defective mutant niger1 is unable to express the canonical enzyme. The infected mutant was unable to induce NBAD and showed higher mortality than the equivalent wild type. Significantly, NBAD showed antimicrobial properties in vitro. These results indicate that synthesis of NBAD is a novel aspect of the overall innate immune response in insects, which likely reinforces the action of the well-known antibacterial peptides