Jasmonic acid- and salicylic acid-mediated defense signal transduction in rice

A combination of molecular, biochemical, and genomic approaches is being used to study jasmonic acid (JA)- and salicylic acid (SA)-mediated defense signal transduction in rice. By generating and analyzing SA-deficient transgenic rice, we have demonstrated that SA acts as a preformed antioxidant to modulate redox balance and prevent rice plants from suffering from oxidative damage caused by aging and biotic and abiotic stresses. In contrast, JA appears to function as an important signal molecule in rice for inducing systemic acquired resistance against pathogen infection. To gain further insights into SA- and JA-mediated defense signal transduction in rice, we isolated a large number of JA-, benzothiadiazole (BTH)-, and/or blast fungus-induced immediate early (IE) genes, whose transcription is independent of de novo protein synthesis. Sequence analysis shows that these IE genes encode putative protein kinases, transcription factors, and other potential signaling components. A JA-inducible IE gene that encodes a Myb transcription factor was found to be associated with blast infection and lesion formation by promoting host cell death. Further analysis of these IE genes will not only enhance our understanding of defense signal transduction in rice, but also facilitate the development of novel strategies for disease control.