Yuji Inagaki, Professor
Ph.D. 1995, Department of Biology, Faculty of Sciences, Nagoya University, Japan.Postdoctoral research fellow in JT Biohistory Research Hall, and Dalhousie University, Canada. 2005-current, Associate Professor, Graduate School of Life and Environmental Sciences, University of Tsukuba. The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology, The Young Scientists’ Prize 2007. Young Scientist Initiative Award 2008, Society of Evolutionary Studies, Japan.
Motivation—Building the global phylogeny of eukaryotes
All living organisms on earth were evolved from a single common ancestral cell, and diverged into three “domains,” namely Bacteria, Archaebacteria, and Eukarya. Needless to say, biological evolution has never stopped until today creating numerous numbers of living organisms. One of the most important and difficult questions in biology is to deduce the evolutionary relationship amongst all the life forms on earth—building the universal tree of life.
The central focus of our research is to gain insight into origin and early evolution of eukaryotes (members of one of the three domains, Eukarya). According to the results from pioneering studies, the vast majority of eukaryotes most likely belong to any of ten major assemblages. One of the goals of this research is to reconstruct the relationship amongst the major taxonomic groups in Eukarya, and this issue has been tackled by using molecular phylogenetic techniques.
Method—Analyzing ‘phylogenomic’ data comprising >100 gene sequences
Until recently, phylogenetic trees used to be constructed from the information of a single gene or a few genes. However, the information of a single gene is insufficient to make a robust phylogenetic inference on ancient events like separations of major eukaryotic groups. To counter the difficulty in single-gene analyses, sequence data consisting of more than 100 genes have been considered in recent phylogenetic analyses. These ‘phylogenomic’ analyses successfully provided insights into the relationship between major eukaryotic assemblages.
Fig.1 Phylogenetic tree
We are specifically interested in several eukaryotic groups, such as haptophytes, cryptophytes, Discoba, and Fornicata, as these may hold the key to understand eukaryotic cell evolution, particularly the evolutions of two important organelles—mitochondria and plastids (or chloroplasts). Haptophytes and cryptophytes are photosynthetic eukaryotes bearing plastids, and these two photosynthetic lineages and their close relatives are significant to address when and how plastids were established in eukaryotes. Discoba is known for the group containing a species with the most ancestral mitochondria, while many members of Fornicata lack classical mitochondria. Thus, we expect that these two groups are important to study the evolution of mitochondria.
Currently we are on the way to phylogenomic analyses of the organisms described above. Since a reliable phylogenetic inference simultaneously requires numerous genes and species, a large scale data analysis using high performance computers play a key role in our study.
Molecular Evolution of Microbes (Japanese)