A novel jasmonic acid-inducible rice myb gene associates with fungal infection and host cell death

Endogenous signal molecules such as jasmonic acid (JA) and salicylic acid ( SA) play an important role in induced resistance against pathogen infection and insect herbivory, In rice seedlings, JA is an effective inducer of sys temic acquired resistance (SAR) against infection of blast fungus (Pyricula ria grisea), To gain further insights into JA-mediated defense signaling pa thways, we isolated and characterized a pathogen- and JA-induced rice gene (JAmyb) that encodes a Myb transcription factor. The JAmyb gene was induced within 1 day after fungal infection in resistant and susceptible interacti ons prior to lesion formation. Unlike most defense-related genes that are a ctivated faster and stronger in resistant interactions, JAmyb induction by blast fungus is much higher in susceptible interactions, accompanied by lar ge lesions and extensive tissue damage. Significant induction of JAmyb also was observed during cell death and lesion formation in certain lesion mimi c mutants. Interestingly, JAmyb was activated rapidly by JA or wounding, in dependent of de novo protein synthesis, but not by other endogenous signal molecules such as SA and abscisic acid or SAR inducers such as benzothiadia zole and probenazole. We used SA-deficient transgenic plants to further dem onstrate that depletion of SA in rice did not abolish but rather enhanced b last-induced JAmyb expression. These results suggest that JAmyb is related closely to host cell death and is involved in the JA-mediated, SA-independe nt signaling pathways in rice.