Induction of a special innate immune response in epidermis of Ceratitis capitata (Diptera, Tephritidae) and Tenebrio molitor (Coleoptera, Tenebrionidae)

TURDERA, L; QUESADA-ALLUÉ L.A.; PÉREZ, M.M.; LOPEZ LASTRA, CLAUDIA; TURDERA, L; QUESADA-ALLUÉ L.A.; PÉREZ, M.M.; LOPEZ LASTRA, CLAUDIA

Mendoza

Congreso; X Congreso Argentino de Entomología; 2018

Sociedad Entomológica Argentina

Insects trigger a multifaceted innate immune response to fight microbial infections. We previously demonstrated that after a microbial (bacteria and yeast) challenge N-β-alanyldopamine (NBAD) is synthesized in the insect epidermis. The aim of this work was to demonstrate that NBAD-synthase (NBAD-S), the enzyme that synthesizes NBAD, is induced in response to infection by the entomopathogenic fungus Beauveria bassiana (Ascomycota, Hypocreales). We tested the pathogenicity of two novel strains of B. bassiana selected for their infectivity in dipterans (strain 436) and coleopterans (strain 075) in the Medfly C. capitata and in the mealworm T. molitor. Infections were induced by topical administration or by a puncture. NBAD-synthase activity was measured in a cell free reaction using dopamine and [C14]-beta-alanine as substrates analyzing the product [C14]-NBAD in a Rackbeta 1214 scintillation counter. Here we show for the first time the ability of entomopathogenic filamentous fungus to induce a special innate immune response. We demonstrated using cell-free extracts the induction of the NBAD-S in both insects. We show that B. bassiana 436 is pathogenic for C. capitata when topically administered with a suspension of 1.106 conidia/mL. When infected, survival in the medfly was 19 ± 1.73 days compared to controls 32 days. No significant differences were observed between sexes. Surprisingly, the strain 075, entomopathogenic for coleopteran, also proved to be infective for dipteran using the puncture method. Larval malformations in C. capitata were observed in sublethal infections with the strain 436 in C. capitata, whereas strain 075 induced in some cases unusual cuticle tanning in T. molitor adults. Although the insects reinforced the cellular and humoral main immunological system by expression of the NBAD-S, in most cases they were unable to neutralize the fungal infection.