Dr. Seiichi FURUKAWA

 ＞Molecular mechanisms of insect innate immune system.

 ＞Interactions between the host immune system and parasitoids.

Molecular mechanisms of insect innate immune system

Insect cellular immune reactions differ depending on the target species. Phagocytosis is activated to scavenge microorganisms such as bacteria and fungi. On the other hand, larger invaders such as parasitoid wasps are eliminated by activation of encapsulation. In this study, we hypothesized that novel determinants regulate cellular immunities independent of surface molecular pattern recognition involving pattern recognition receptors (PRRs). Immune-related genes differentially expressed depending on the treated material size were screened in larval hemocytes of the rice armyworm, Mythimna separata. Consequently, we identified a novel C-type lectin gene up-regulated by injection of large beads but not small beads of identical material. Examination of in vitro effect of the recombinant protein on the immune reactions clarified that the protein activated encapsulation reaction, while it suppressed phagocytosis. These results suggest that this novel C-type lectin designated ‟encapsulation promoting lectin (EPL)" regulates cellular immunity by a novel immune target size-recognition mechanisms.

Interactions between the host immune system and parasitoids.

The tachinid fly Drino inconspicuoides (Diptera: Tachinidae) is an ovolarviparous endoparasitoid whose larvae develop in the host haemocoel and avoids the host immune system. In this study, we investigated the immune evasion mechanisms of this species during infestation in the host Mythimna separata (Lepidoptera:Noctuidae). We discovered a unique ‘cloak’ that surrounded D. inconspicuoides larvae that penetrated into the host and determined through genomic polymerase chain reaction analysis that this structure originated from the host rather than the tachinid. The  ‘cloak’ contained both haemocytes and fat body cells from the host, with the haemocytes assembling around the larvae first and the fat body cells then covering the haemocyte layer, following which the two mixed. Living D. inconspicuoides larvae that were wrapped in the ‘cloak’ were not melanized whereas encapsulated dead larvae were melanized, suggesting that this structure contributes to the avoidance of host immune reactions.

Dr. Kazumu KURAMITSU

Biology, behavior and ecology of parasitoid wasps, and interaction with their host insects

Key words: host-parasitoid interactions, plant-insect interactions, tri-trophic interactions, behavioural ecology, chemical ecology

Parasitoids are insects whose larvae parasite in/on their arthropod hosts (normally insects) and develop by feeding on the host’s body. Larval feeding results in the death of their host. They are a significant mortality factor in the population of many insects. Based on both field surveys and laboratory experiments, we study biology, behavior and ecology of parasitoid wasps, and parasitoid-herbivorous host-host’s food plant interactions.

Dr. Jun TABATA

Chemical ecology of insects: sex pheromones and species differentiation