Role of Ethylene, Abscisic Acid and MAP Kinase Pathways in Rice Blast Resistance

A combination of genetic, molecular, biochemical and pathological approaches have been taken to elucidate the defense signaling pathways leading to rice blast resistance and susceptibility. Using transgenic rice lines defective in salicylic acid (SA) or jasmonic acid (JA) pathways, we have previously shown that SA is not an effective signal molecule in rice but acts as a constitutive antioxidant to protect rice plants from the pathogen-induced oxidative damage. On the other hand, JA pathway is involved in mediating rice defense gene expression and blast resistance. Recently, increasing evidence suggests that ethylene (ET) biosynthesis is important for rice blast resistance. Based on the analysis of transgenic rice lines defective in ET, abscisic acid (ABA), or mitogen-activated protein (MAP) kinase pathways, we have demonstrated that ET and its antagonistic interaction with ABA plays a crucial role in rice blast resistance. Furthermore, a stress-responsive MAP kinase was found to mediate the cross-talk between ABA and ET pathways and inversely regulate rice blast resistance and abiotic stress tolerance.