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Isochorismate-derived biosynthesis of the plant stress hormone salicylic acid.

Science (New York, N.Y.) (2019-08-03)
Dmitrij Rekhter, Daniel Lüdke, Yuli Ding, Kirstin Feussner, Krzysztof Zienkiewicz, Volker Lipka, Marcel Wiermer, Yuelin Zhang, Ivo Feussner
ABSTRACT

The phytohormone salicylic acid (SA) controls biotic and abiotic plant stress responses. Plastid-produced chorismate is a branch-point metabolite for SA biosynthesis. Most pathogen-induced SA derives from isochorismate, which is generated from chorismate by the catalytic activity of ISOCHORISMATE SYNTHASE1. Here, we ask how and in which cellular compartment isochorismate is converted to SA. We show that in Arabidopsis, the pathway downstream of isochorismate requires only two additional proteins: ENHANCED DISEASE SUSCEPTIBILITY5, which exports isochorismate from the plastid to the cytosol, and the cytosolic amidotransferase avrPphB SUSCEPTIBLE3 (PBS3). PBS3 catalyzes the conjugation of glutamate to isochorismate to produce isochorismate-9-glutamate, which spontaneously decomposes into SA and 2-hydroxy-acryloyl-N-glutamate. The minimal requirement of three compartmentalized proteins controlling unidirectional forward flux may protect the pathway against evolutionary forces and pathogen perturbations.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Protease Inhibitor Cocktail, for plant cell and tissue extracts, DMSO solution
Sigma-Aldrich
L-Lactic Dehydrogenase from rabbit muscle, Type II, ammonium sulfate suspension, 800-1,200 units/mg protein
Sigma-Aldrich
4-Hydroxybenzoic acid, ReagentPlus®, 99%
Sigma-Aldrich
Salicylic acid, BioXtra, ≥99.0%
Sigma-Aldrich
Myokinase from rabbit muscle, ammonium sulfate suspension, 1,500-3,000 units/mg protein (biuret)
Sigma-Aldrich
Pipecolinic acid, 98%
Sigma-Aldrich
Chorismic acid from Enterobacter aerogenes, ≥80%
Sigma-Aldrich
Amyloid Protein Non-Aβ Component, ≥80% (HPLC)