Abstract
One of the earliest plant immune responses is the oxidative burst, in which levels of reactive oxygen species (ROS) rapidly increase. ROS generation after recognition of avirulent strain was strongly suppressed by Ca2+ chelating agent or kinase inhibitor. In order to investigate the Ca2+ dynamics during plant immune responses, yellow cameleon 3.6 was transiently expressed in cultured rice cells. When the avirulent strain was infected to the rice cells, rapid increase of Ca2+concentration was observed, while a notable change was not observed by virulent strain. The data indicated the possibility that calcium-dependent protein kinase (CPK) possessing EF hand motifs and kinase domain was one of the candidate molecules involved in induction of immune responses. Among 29 CPK genes, 6CPKgenes were induced during plant immune responses. RNAi knock-down experiments showed that OsCPK12 regulated the ROS generation during the immune responses. Interaction between OsCPK12 constitute active form and Osrboh (rice respiratory burst oxidase homologs) which is involved in ROS generation was examined using BiFC technology. OsCPK12 interacted with N-terminal domain of OsrbohA.
