Model of salicylic acid (SA) synthesis and SA signal transduction

Model of salicylic acid (SA) synthesis and SA signal transduction. Enhanced disease susceptibility 1 (EDS1), phytoalexin-deficient 4 (PAD4), and avrpphb susceptible 3 (PBS3) are involved upstream of SA synthesis, and can be induced by positive SA feedback. The redox state alteration caused by the SA burst leads to the monomerization of non-expressor of PR genes 1 (NPR1). The monomerization of NPR1 by thioredoxins (TRXs) such as TRX-H3 and TRX-H5 cause the translocation of NPR1 in the nucleus and subsequent interaction with the positive transcription activators TGACG sequence-specific binding proteins (TGAs), the negative regulators non-inducible immunity (NIM1)-interacting proteins (NIMINs) and Suppressor of npr1-inducible 1 (SNI1). NPR1 is imported into the nucleus through nuclear pores. S-nitrosoglutathione (GSNO) can facilitate the oligomerization of NPR1. During systemic acquired resistance (SAR), the kinase SnRK2.8 is required for the phosphorylation of NPR1, which is not triggered by SA; it is triggered by an unknown signal. A possible working model would be that SA triggers the formation of NPR1 monomers. Then, NPR1 monomers are phosphorylated by sucrose non-fermenting 1 (SNF1)-related protein kinase 2.8 (SnRK2.8) for its nuclear import. The transcription factor whirly 1 (WHY1) is probably involved in the NPR1-independent SA response. Suppressor of SA insensitivity 2 (SSI2) is a negative regulator, independent from NPR1, which regulates the SA-mediated response. Overexpression of glutaredoxin C9 (GRXC9) could regulate the SA pathway independent from NPR1. Pathogen-related 1 (PR1), PR2, and PR5 are SA-responsive marker genes. Activation (closed arrowhead), suppression (⊥), and important genes are indicated.

Publication

Different Pathogen Defense Strategies in Arabidopsis: More than Pathogen Recognition. (2018) Wei Zhang, et al. Cells. 2018 Dec;7(12):252. Figure: F1. All organisms Arabidopsis thaliana Solanum lycopersicum Homo sapiens Caenorhabditis elegans

Disease mentions