Elucidation of Signaling Pathway in Plant Immunity
1. New Discovery in Function of R Protein
Resistance (R) proteins, which work as interdellular receptors perceiving invasion of pathogens, is extremely important molecule in innate immunity of plants. However, it has been unknown with what signaling molecule R protein induces plant immunity. Recently we found out that the interaction of OsRac1 to R protein for rice blast fungus activates OsRac1. We also made clear that, by activating OsRac1 and controllong active oxygen and hypersensitive apoptosis, Pit controls resisitance to rice blast fungus. Moreover, we are analyzing the activation mechanism of OsRac1 with R protein.
2. New Discovery on Maturation of Transmembrane Immunoreceptor and on Intracellular Transport
Little is known about the mechanism of maturation and tranport of transmembrane immunoreceptors which localize on cell membrane. We found out that components of "Defensome," Hop/Sti1 and Hsp90, directly bind with the chitin receptor. In addition, we made clear that the RNAi of Hop/Sti1 observes unusual localization of chitin receptor and resisitance to rice blast fungus is suppressed. Therefore, it is suggested that Hop/Sti1 binds directly to the chitin receptor and is involved in transport to membrane and maturation in plasma membrane. Mechanisms of maturation of receptors and intracellular transport are to be elucidated with Hop/Sti1 as molecular basias.
3. Establishment of Defensome Model which Controls Immune Reaction in Rice
By proteome analysis, we identified RAR1, HSP90, RACK1 and Hop/Sti1 as factors consisting OsRac1 complex, "Defensome" and elucidated that those proteins play critical roles in diisease resistance. Through several analyses, we found out that OsRac1 comoplex Defensome is a very large protein cmplex.(See Fig3)
