Understanding intaractions between organisms targeted at the endosymbiosis in insects. – Bioproduction Research Institute, the National Institute of Advanced Industrial Science and Technology

In nature, organisms are living in close association with surrounding physical environment as well as other organisms. Thus, each of the organisms is regarded as a component of the ecosystem. Considering the diverse microbial community found inside the organisms in general, each of the organisms can also be regarded as constituting an ecosystem.

Fig. 1. (Left) Pea aphids on a broad bean seedling. (Right) In the aphid body, symbiotic bacteria with important biological roles are harbored in specialized cells. *Buchnera* (green) is essential for survival and reproduction of the host aphid. Serratia (red) confers a resistance to high temperature on the host aphid, and can compensate for the essential biological roles of *Buchnera*. Blue shows aphid’s nuclei.

Many animals and other organisms constantly harbor microorganisms inside their body, which has been referred to as “endosymbiosis”. Due to the close spatial proximity, extremely intimate biological interactions and inter-dependency are commonly found between the partners called host and symbiont. Novel biological properties are often generated through such associations. In many cases, host and symbiont are integrated into an almost inseparable entity.
　　

Fig. 2. (Left) *Spiroplasma* sp. (Right) Surprisingly, fruit flies infected with the spiroplasma produce all female offspring. The reproductive phenotype, called male-killing, is regarded as a selfish strategy of the maternally-transmitted symbiont.

Fig. 3. (Left) Adzuki bean beetle. (Right) On the X chromosome of the beetle, a large bacterial genome fragment derived from an insect endosymbiont of the genus *Wolbachia* was identified. The host-symbiont horizontal gene transfer is of evolutionary interest.

Our main research targets are diverse endosymbiotic interactions found in insects. We are also interested in sophisticated biological interactions associated with such phenomena as parasitism, reproductive manipulation, morphological manipulation, animal sociality, etc. Mechanisms underlying these biological interactions are investigated by using multi-disciplinary approaches including molecular biology, genetics, physiology, ecology and evolutionary biology.