| Research Abstract |
Molecular basis of oxidative burst (OXB) system, which was an initial signal for induction of defense response in plants, regulatory mechanisms for activation of the system, and dynamic phases of molecular and physiological changes associated with local or systemic induced resistance were investigated for understanding of a systematic mechanism of plant active defense under the control by oxidative burst Following results were obtained :
1 ) Two gp91phox horologes, which may be a subunit of NADPH oxidase, were cloned from potato and tobacco plants, respectively, and they were characterized by membrane fern proteins with binding sites of NADPH and calcium,
2 ) The OXB system was rapidly activated from inactive state by wounding or infection stimuli and OXB in the potentiated cells was inhibited by Ca^<2+> channel blockers, calmodulin inhibitors or protein kinase inhibitors, suggesting involvement of a C kinase in induction of OXB.
3 ) Defense-metabolism-related genes, which were stimulated by OXB-inducible elicitors, were cloned by mean of differential display or subtraction,
4 ) Gene silencing about some of the cloned genes by using a PVX vector demonstrated that genes responsible for OXB or NADPH producer were a crucial role in defense expression against incompatible Phytophthora fungus.
5 ) Induction of local OXB caused local as well as systemic induced resistance, dispatching a noble systemic signal which caused a sequential Ca^<2+> influx from cells to cells in non potentiated tissues and then induced systemic OXB at the potentiated tissue for triggering induction of systemic acquired resistance.
6 ) A positive regulation of induction of OXB system by signal dispatching elements was suggested to be applicable for induction of plant immunization against pathogens.
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