Graduate School of Frontier Sciences, The University of Tokyo Department of
Integrated Biosciences

My research interests center on the origins of chloroplasts (plastids). You might have an image of biologists as people who have loved living things since childhood, catching insects, watching birds, learning the names of plants and flowers, and running around the fields until dark, but I wasn't that type at all. To be honest, I can also say that I am not interested in living organisms themselves, but that they happen to be the most suitable targets for the purpose of the "search for origins" in which I am interested.

Biological phenomena can be understood in terms of "patterns" and "processes." The textbook often says that endosymbiosis gave rise to chloroplasts, which is a way of understanding biology as a pattern, similar to saying that humans originated in Africa. However, what I really want to know is "How?", in other words, what kind of process was vital to achieve that. Certain types of endosymbioses in which photosynthetic organisms are internalized in other organisms’ cells, such as the one that gave rise to chloroplasts, are sometimes referred to as "photosymbiosis." To address the mystery of the origin of this photosymbiosis, we are analyzing the genome information and cell structure of algae that retain ‘ancestral’ properties. We are also investigating various ongoing endosymbiotic phenomena that are widespread in nature, such as the one between coral symbiotic algae and cnidarian animals, to clarify the universal mechanisms common to photosymbiosis. We are also conducting research to understand the relationships between macroscopic life events and symbiosis, such as coral bleaching and mass spawning.

Symbiosis may seem like a peculiar phenomenon, but as we can see from the examples of symbiosis between humans and gut bacteria, it is quite fair to say that almost all living things on Earth have symbiotic relationships with others. From the viewpoint of symbionts, the host organism's body and cells are one of the diverse ‘natural’ environments, and can be seen as an opportunity to expand its potential to compete for survival. The symbionts’ responses to its host is also a realization of the universal flexibility of living organisms, just as an extension of their responses to natural environments. We aim to understand the common principles of photosymbiosis by conducting multi-scale analyses of these symbiotic mechanisms from molecules to systems including cells, individuals, and environmental responses.