Research Director: Dr. Junya Mizutani
(Professor, Faculty of Agriculture, Hokkaido University)
Research Term: 1988-1993

During the long course of evolution most wild species of plants developed resistance to both pests and diseases using what are now called alleohemicals. This project focused on such plant ecochemicals, while aiming at elucidating the defence mechanisms by studying the production, role and eventual fate of the secondary metabolites in the ecosystem.

Research Results

New model for a defence system of plant leaves: A symbiotic interaction between Polymnia sonchifolia and epiphytic bacteria has been found and elucidated for the first time. A gene which coded the hydroxycinnamic acid decarboxylase in the bacteria has been successfully transferred intoEscherichia coli.

Cytochrome P-450 for the formation of capsidiol: The importance of cytochrome P-450 was found for the formation of sesquiterpenoid phytoalexin, capsidiol in green pepper. 5-Epi-aristolochene 3-hydroxylase induced by a treatment of arachidonic acid as an elicitor was isolated and identified as an inducible cytochrome P-450 of 59 kDa.

New class of allelochemicals: A disaccharide derivative designated as lepidimoide, has been isolated and identified from the mucilage of germinated cress seeds.

Chemiluminescence assay for lipid peroxidation: Regarding an early responses due to stress, the generation of active oxygen and a subsequent lipid peroxidation were for the first time observed using soybean cell suspension seedlings after a treatment with the fungal elicitor by means of a CL (chemiluminescence) assay and the CL-HPLC technique with ultrahigh sensitivity.

Insect micro dialysis system: The applicability of "micro dialysis" as an advanced sampling technique for the analysis of insect haemolymph has been investigated. This research was available for continuous sampling of Spodoptera litura haemolymph; samples were analyzed by HPLC with a coulometric electrochemical detector for the determination of octopamine and dopamine.

N2-driven particle gun: Successful delivery of alleochemicals such as lepidimoide, plasmid DNA (which has a GUS gene) and genomic RNA of the sweet clover necrotic mosaic virus into plant samples in situ has been demonstrated by using an improved particle gun driven by controllable compressed nitrogen gas. The results show that this gun technique is efficient for the introduction of biologically active substances, DNA and RNA into intact plant cell.

A Model for a Defensive Chemical Interaction between Host Plants and Epiphytic Bacteria.

A wild plant (rugosa rose) contains ecochemicals