Iwate University 21st Century COE Program

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Yasushi Saitoh - Cell Biology, Molecular Biology -
ysaitoh@
Associate Professor
United Graduate School of Agricultural Sciences
Cryobiosystem Research Center, Faculty of Agriculture

Strategic mechanism of biological systems for thermal energy
- Molecular mechanism of overwintering dormancy in plant system under cold environment -

I. Research achievements
My focus of research has been placed on genome, chromatin and chromosome structures. Recently, the important roles of the change of these structures have started drawing attention. In plants, we have just started to understand the regulation system of gene expression by the changes of chromatin structure using histone modifications and DNA methylation. Upcoming studies of these structures should play important roles in the understanding of differentiation and the regulation of gene expression in plants.

We have also been carrying out research in comprehensive understanding of the control system of DNA replication and transcription with an aim to understand the cell differentiation mechanism with a new perception. While detailed analyses of the genomic replication origin have been made with yeasts and produced substantial outcomes, the replication origin mechanism of yeasts cannot be applied directly to higher eukaryotic cells. More research, therefore, is needed for the understanding of the higher eukaryotic specific mechanism of the replication origin determination. In such circumstances, we published an entirely new model of the origin determination mechanisms of DNA replication that is unique to higher multicellular organisms. I believe that this is an important topic to study for the understanding of cell differentiation and exclusive control of differentiation and cell division (i.e., higher cell division rate prevent cell differentiation).

In the evaluation by the National Institute for Academic Degrees and University Education for the study programs started in the academic year 2002, this study was evaluated as the "most excellent and highly innovative" study, as well as the study that has "excellent" social influence.

II. Goals in the COE Program
Research of wintering buds of gentian plants
After some growth of shoots, the wintering organs of winter-hardy plants stop their growth as preparation for over-wintering. The mechanism of suspending cell divisions by these organs must be related to the establishment of low-temperature and freezing tolerance of the plants. Among the wintering-bud-specific proteins and genes that have been identified, many are known to increase the level of expression in response to low temperature stresses in other plants. More interestingly, these proteins are found to increase the expression level in the wintering buds even prior to exposure to low temperatures. This suggests that wintering buds may stop cell division and start acquiring chilling and freezing tolerance in preparation for the upcoming low-temperature environment. We are planning to study the relationship of these mechanisms with arrest of cell division and chilling and freezing tolerance as well as interaction and communication systems among these and other proteins. In addition to studying these mechanisms from the perspective of the individual gene hunting, we are also aiming to carry out a study with a focus on the structural changes of chromosomes, nuclei and chromatins as well as the changes in transcription, replication and gene expression control systems.

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