Syracuse

Revealing insect resistance mechanisms in a host-parasitoid interaction

Archive ouverte

Gornard, Samuel | Germon, Isabelle | Borday-Birraux, Véronique | Dulac, Claire, Capdevielle | Kaiser-Arnauld, Laure, Marie-Paule | Mougel, Florence

Edité par CCSD -

International audience. Insects are subject to infectious organisms and defend themselves with an innate immune system, as they are generally thought to lack acquired immunity. The innate defense is divided between humoral immunity, which consists in multiple anti-pathogen molecules, and cellular immunity, which is based on hemocytes. Those cells are able to discard larger invaders, either by phagocytosis or encapsulation. The latter is used against large foreign bodies, and consists in enclosing them in a multi-layer cellular shell, which will produce toxic compounds and melanin in addition to preventing interactions with other tissues. Parasitoid eggs, when triggering immune system, are killed by this phenomenon. Our study focuses on the host/parasitoid couple formed by the Lepidopteran stem borer Sesamia nonagrioides and the Hymenoptera Cotesia typhae. Parasitism success of a C. typhae strain is low on the French S. nonagrioides population due to encapsulation. To study the dynamic of capsule formation and the targeted egg or larval stages, we used several methods and compared their results. First, we dissected non-resistant hosts to characterize parasitoid larval development. We then dissected resisting hosts to retrieve and observe capsules under microscopy, especially because they do not melanize and are hard to detect. We labelled their hemocytes with immunohistochemistry techniques to identify their populations, and finally, we checked for the structural arrangement of the capsules with histology sectioning. Together, those methods gave us a broad understanding of capsule formation dynamics and of the cell populations involved.

• Description
• Sujet/Public
• Outil
• Outil d'anticipation
• Mémoire et thèse
• Gestion