Research Title

Relationship between differentiation and secondary metabolites production in plants.
Elucidation of biosyntheses of plant secondary metabolites.
Dynamics and Function of plant secondary metabolites.
Interrelation between plants and environments.
Breeding and reservation of Medicianl Plants.

Production and regulation of useful plant secondary metabolites in plant tissue cultures.
Diverse plant secondary metabolites have been used as medicines, agrichemicals, spices, sweetenings, pigments and cosmetics. They are also expected as the leading compounds for the establishment of the unique, original drugs having low-side effects. In recent three decades, the production of such useful secondary metabolites in plant tissue cultures has been energetically investigated. However, most attempts to the efficient production of these compounds were in failure owing to the lack of knowledge about the regulatory mechanisms of their production and the roles of these compounds in the life of the plants.
In the laboratory of medicinal plant garden, we are investigating the regulatory mechanisms of secondary metabolites production in plant cells, that is, biosyntheses, transports and accumulations of them, and the relationship between expressions of biosynthetic abilities and differentiation of plant cells, from the sites of phytochemical, plant biochemical, plant physiological and molecular biological aspects, for the sake of the designed and efficient production of useful secondary metabolites in plant tissue cultures.

1. Relationship between the differentiation of plant cells and the production of secondary metabolites.
The expression of secondary metabolism in plant cells is closely related to the differentiation of plant cells, and it is often observed that the lack or the low productivity of secondary metabolites in de-differentiated plant cells. For the solution of this problem, it is necessary to clarify the differences between differentiated cells which posses the secondary metabolites productivity and de-differentiated cells lacking it. We are investigating the biosynthetic route of loganin, the central intermediate of pharmaceutically important indole alkaloids, for the identification of key enzyme of loganin biosynthesis, whose gene expression is inhibited in de-differentiated cells.

2. Participation of the secondary metabolites-accumulating tissues on the production of secondary metabolites.
Cork tissues, which had been thought to be a passive accumulation site of lipophilic secondary metabolites, stimulate the production of such compounds in de-differentiated plant culture cells. This phenomenon suggests that plural differentiated tissues, not only the actual biosynthetic cells but also their surrounding cells, cooperatively regulate the secondary metabolism. To establish this hypothesis, the assay of the active principle in cork tissues which stimulate the secondary metabolites production, and the clarification of its regulatory mechanism are studying.

3. Artificial regulation of secondary metabolism.
Plant cells produce different secondary metabolites, the origins of which are closely correlated. By the suppression of the expendable metabolic flow, the improvement of the potential abilities of the supply of the precursor and the specific and more efficient production of designed useful compound is expectable. The artificial regulations of secondary metabolism in plant cells such as boraginaceous, umbelliferous and solanaceous plants, by use of plant physiological and molecular gentetical methods, are undertaking.