The main sclerotization precursor of insect Brown cuticles is also an essential component of the Innate innunity

MARTIN PEREZ; LUCIA TURDERA; JULIETA SCHACHTER; CLAUDIA LOPEZ LASTRA; LUIS A. QUESADA ALLUE

Congreso; 9TWWH Meeting of Tephritid Workers of the Western Hemisphere; 2016

Insets trigger a multifaceted innate immune response to fight microbial infections. The first line of response to microbial entry is mediated by the rapid action of phenoloxidases present in the integument and hemolymph. These enzymes generate quinines that lead to localized melanizaion and crosslinking, eventually encapsulating invaders. N-β- alanyldopamine (NBAD) is the main sclerotization precursor of insect brown cuticles. This compound is oxidized to NBAD- quinone by the phenoloxidases during the sclerotization process, in order to generate the cuticle crosslinking. We ascertained if N-β- alanyldopamine (NBAD) is involved in the innate immune response too. Insects were injected with microorganisms (bacteria, yeast), polysaccharides or spores of the entomopathogenic fungus Beauveria bassiana and the activation of NBAD- synthasa was assessed. We show that septic injuries induce the syntehesis of NBAD in Ceratitis capitata and Tenebrio molitor. We demonstrate 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 cuticle molt. In C. capitata this enzyme is coded by the gene niger and the defective mutant niger 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, for the first time, that synthesis of NBAD is a novel function of the overall innate immune response in insects.