Proteomic analysis of salicylic acid-induced resistance to Magnaporthe oryzae in susceptible and resistant rice

To probe salicylic acid (SA)-induced sequential events at translational level and factors associated with SA response, we conducted virulence assays and proteomic profiling analysis on rice resistant and susceptible cultivars against Magnaporthe oryzae at various time points after SA treatment. The results showed that SA significantly enhanced rice resistance against M. oryzae. Proteomic analysis of SA-treated leaves unveiled 36 differentially expressed proteins implicated in various functions, including defense, antioxidative enzymes, and signal transduction. Majority of these proteins were induced except three antioxidative enzymes, which were negatively regulated by SA. Consistent with the above findings, SA increased the level of reactive oxygen species (ROS) with resistant cultivar C101LAC showing faster response to SA and producing higher level of ROS than susceptible cultivar CO39. Furthermore, we showed that nucleoside diphosphate kinase 1, which is implicated in regulation of ROS production, was strongly induced in C101LAC but not in CO39. Taken together, the findings suggest that resistant rice cultivar might possess a more sensitive SA signaling system or effective pathway than susceptible cultivar. In addition, our results indicate that SA also coordinates other cellular activities such as photosynthesis and metabolism to facilitate defense response and recovery, highlighting the complexity of SA-induced resistance mechanisms.