Over-expression of chloroplastic lipoxygenase RCI1 causes PR1 transcript accumulation in transiently transformed rice

The acquired resistance state of rice plants, rendering them resistant to subsequent infections with virulent pathogens, can be triggered by treatments with non-host pathogens, necrotizing pathogens and certain chemicals. The 13-lipoxygenase RCI1 ( LOX2:Os:2) is induced specifically following treatment with chemical inducers of resistance. Here, we report that the over-expression of RCI1 in a transient transformation assay leads to PR1 transcript accumulation in rice leaves. In addition, we show that this property is due to the enzymatic activity of the transgenic protein. Furthermore, exogenous application of (13 S,9 Z,11 E,15 Z)-13-hydroxy-9,11,15-octadecatrienoic acid (13-HOT), an oxylipin deriving from the reductase branch of the lipoxygenase pathway, is capable of inducing PR1. These results support a role for RCI1 in the generation of signalling molecules during the establishment of the acquired resistance response in rice.