Completing the pathway: Salicylic acid biosynthesis and its role in disease resistance in Arabidopsis thaliana
M. STEINWAND (1), M. Strawn (2), M. Wildermuth (1) (1) University of California Berkeley, U.S.A.; (2) Boehringer Ingelheim, U.S.A.

The phytohormone salicylic acid (SA) mediates many plant processes, and is crucial for host defense response signaling upon challenge by (hemi)biotrophic pathogens. Despite the importance of salicylic acid to disease outcomes across many agronomically important plant species, knowledge of its biosynthesis remains incomplete. Initial biochemical studies pointed to the amino acid phenylalanine as the precursor to SA, though no full pathway has been defined. Instead, previous work from our lab found that the Arabidopsis thaliana gene Isochorismate Synthase 1 (ICS1, SID2) is responsible for >90% of pathogen-induced SA, suggesting that the chloroplast metabolite chorismate serves as the dominant precursor to induced SA production (Nature 414:562). ICS1 is plastidic and monofunctional (J Biol Chem 282:5913); therefore an additional enzyme appears necessary for the final conversion of isochorismate to SA. Structural modeling based on similarity to the bacterial protein PchB, which converts isochorismate to SA, identified a class of Arabidopsis proteins likely to have isochorismate pyruvate lyase activity (IPL). We have characterized the biochemical properties of these enzymes and altered their expression in planta to identify the final step in pathogen-induced SA biosynthesis in Arabidopsis.

Abstract Number: P16-474
Session Type: Poster