Rice Genetics IV - IRRI books - International Rice Research Institute

Molecular signaling in diseaseresistance of riceK. Shimamoto, A. Takahashi, and T. KawasakiWe study signaling pathways involved in the interaction of rice and the riceblast fungus, Magnaporthe grisea, by using molecular and genetic methods.We recently demonstrated that the rice homologue of the small GTPase Racis an important molecular switch for resistance gene–mediated disease resistanceagainst rice blast infection. Furthermore, it was shown to activatethe production of reactive oxygen species as well as cell death, both of whichare often observed during the resistance response to avirulent pathogens inmany plant systems. In another approach, we study lesion-mimic mutants ofrice showing increased resistance to the rice blast fungus. Biochemical analysisof these mutants allowed us to identify genes that may play an importantrole in disease resistance of rice.A better understanding of disease resistance reactions occurring in plants will help usdevelop crops with improved resistance to major pathogens. Rice is no exception.Blast, bacterial blight, sheath blight, and tungro virus cause billions of dollars inlosses. Recently, major progress has been made in the molecular biological study ofrice-pathogen interactions (reviewed in Ronald 1997, Wang and Leung 1999). Geneswith resistance against bacterial blight (Song et al 1995, Yoshimura et al 1998) andrice blast fungus (Wang et al 1999, Jia et al 2000) were isolated and lesion-mimicmutants were recently characterized at the molecular level (Takahashi et al 1999, Yinet al 2000). These studies suggest that we have begun to understand the molecularbiology of disease resistance in rice and that rice will become a useful model plant forstudies in plant-microbe interactions in the near future. Despite this recent progress inour understanding of the molecular biology of rice-pathogen interactions, little isknown about the signaling pathways underlying disease resistance in rice.We have been taking molecular biological approaches to study the signaling pathwaysinvolved in rice-blast interactions and some of the recent results are describedhere.Molecular signaling in disease resistance of rice 323