Figure 1.

Pathways of SA biosynthesis in plants. Isotope feeding experiments suggest that plants synthesize SA from cinnamate produced by PAL. Genetic studies have indicated that the bulk of SA is produced from isochorismate. Given the importance of both PAL and ICS in SA accumulation demonstrated from experiments using genetic mutants, gene silencing and chemical inhibition, it is possible that the PAL and ICS pathways are integrated through a metabolic or regulatory grid in SA biosynthesis. The recently identified PBS3 and EPS1 are important for pathogen-induced SA production and may encode enzymes catalyzing related, and possibly sequential, reactions in the synthesis of an important precursor or regulatory molecule for SA biosynthesis.