Lipoxygenases are of biological interest because the primary products of the reaction, fatty acid hydroperoxidase, are typically metabolized into molecules of known or suspected regulatory activity which may function in the response to stress. The goal of the proposed research is to understand the function of lipoxygenase in the Arabidopsis defense response to pathogenic Pseudomonads. The proposed experiments test the working hypothesis that lipoxygenase, rapidly induced upon attack by an avirulent pathogen, is required for disease resistance, and functions in the synthesis of jasmonic acid which serves to regulate the host defense response. The pathogen defense response will be tested intransgenic plants which either over-produce the lipoxygenase cDNA or in antisense plants with reduced levels of lipoxygenase activity. These experiments will provide evidence that the rapid induction of lipoxygenase upon pathogen attack is an important component of an effective host defense response. The spatial patterns of lipoxygenase mRNA, protein accumulation and gene expression will be determined in response to pathogen attack by in situ hybridization, immunocytochemistry and analysis of lipoxygenase promoter/GUS fusions, respectively. Finally, the kinetics of both lipoxygenase induction and jasmonate production inresponse to pathogen attack will be measured to determine the relationship of these two species in signalling. Completion of these experiments will lead to important insights into the role of lipoxygenase in pathogen defense.
