Systemic acquired resistance is an inducible defense mechanism in plants that confers enhanced resistance against a broad-spectrum of pathogens. The activation of SAR requires the translocation of an unknown factor through the phloem. The Arabidopsis thaliana SFD1 gene, which encodes a dihydroxyacetone phosphate (DHAP) reductase, is required for SAR. DHAP reductases catalyze the interconversion of DHAP and glycerol-3-phosphate, which provides the glycerol backbone for glycerolipid biosynthesis. Lipid metabolism is altered in the sfd1 mutant, suggesting that a lipid(s) has an important role in SAR. The long-term objectives of this proposal are to study the role of SFD1 in SAR, thereby testing the above hypothesis. To achieve these objectives, a combination of genetic, molecular and biochemical approaches will be pursued to characterize the biochemical function of SFD1. In addition, the role of a SFD1-derived factor in the phloem during the activation of SAR will be addressed with a novel bioassay in combination with highly sensitive mass-spectrometric approaches. The proposed research will contribute greatly to the understanding of long-distance signaling in SAR. The project will provide an excellent opportunity to integrate state-of-the-art research and education by bringing current knowledge of lipid metabolism and the genetic, molecular and biochemical basis of plant stress responses into the classroom. In addition to providing training to graduate students and post doctoral fellows, this project will engage undergraduates in research in the biological sciences and broaden the participation of underrepresented groups. In particular, an undergraduate student from a non-Ph.D.-granting institution will be recruited to work on the project each summer. Results from this project will have potential benefits to society at large. The lipid(s) identified by the proposed study could provide new targets for enhancing disease resistance in plants, thus limiting the utilization of toxic chemicals to protect plants, thereby improving the quality of our environment and health.
