Spatial and temporal regulation of biosynthesis of the plant immune signal salicylic acid

Significance Biosynthesis of the plant immune signal salicylic acid (SA) is normally induced upon pathogen challenge through transcriptional activation of the key SA synthetic enzyme gene, ICS1 . However, how different pathogenic signals trigger SA synthesis in both local and systemic tissues and during different immune responses is poorly understood. Our study filled this knowledge gap by the identification of two transcription factors (TFs): one is required for SA biosynthesis in stomata to prevent pathogen entry through these epidermal openings, and the other is essential for both the circadian oscillation in SA levels and the accumulation of SA in distal tissue during systemic acquired resistance. Our study shows that SA biosynthesis is regulated by multiple TFs in a spatial and temporal manner.