Abstract
Salicylic acid (SA) is an essential component responsible for disease resistance in some dicotyledonous plants. Increase in SA level is required for induction of systemic acquired resistance in these plants. Rice has the extremely higher levels of SA relative to the dicotyledonous plants, and SA levels does not increase after pathogen infection, suggesting that the role of SA in rice differ from that in dicotyledonous plants. In this study, we characterized transgenic rice plants that express the bacterial nahG gene encoding salicylate hidroxylase, the enzyme that degrades SA. nahG-expressed rice seedlings showed delayed development phenotype, and developed lesions in their leaves without pathogen infection under high-light conditions. In such nahG plants, glutathione pool size decreased and the redox state of glutathione were reduced. These results suggest that the SA in rice is required for maintaining defense mechanism against oxidative damages caused by high-light stress.
