UniPathway-to-GO mapping electronically transfers chorismate-to-isochorismate and salicylic acid biosynthesis pathway terms to ICS1, consistent with the experimentally established monofunctional isochorismate synthase activity of ICS1.

UniProt SubcellularLocation-to-GO mapping yields plastid/chloroplast localization for ICS1, consistent with the experimentally demonstrated plastid stromal localization of ICS1:GFP.

ARBA machine-learning rules propagate isochorismate synthase/chorismate-pathway and lyase-family annotations to ICS1 from the menF/isochorismate-synthase family; treated as supporting context rather than primary evidence for the SA-biosynthesis role.

Combined IEA pipelines (InterPro/UniRule/ARBA) converge on isochorismate synthase activity and chorismate-derived secondary-metabolite biosynthesis terms for ICS1, all consistent with its monofunctional ICS role committing chorismate to the SA pathway.

AtSubP sequence-based prediction assigns ICS1 to the plastid, consistent with the cleavable N-terminal chloroplast transit peptide and with experimentally confirmed plastid-stroma localization.

The SID2 gene encodes isochorismate synthase (ICS1); SA is synthesized from chorismate via ICS, and SA made by this pathway is required for local and systemic acquired resistance.

ics1 mutants are depleted in SA accumulation and altered in resistance to S. aureus; resistance is mediated by SA.

Standalone menF-like ICS genes arose from splitting of the PHYLLO menF module, enabling an independently regulated branch supplying isochorismate for SA biosynthesis separate from phylloquinone biosynthesis.

mlo-based powdery mildew resistance in Arabidopsis does not involve salicylic acid, ethylene or jasmonic acid; it requires a syntaxin, glycosyl hydrolase and ABC transporter.

Stomatal closure is a plant innate immune response restricting bacterial invasion; SA is required for this stomatal defense.

AtICS1 is a plastid stromal, monofunctional isochorismate synthase (Km 41.5 uM for chorismate, kcat 38.7 min-1) that converts chorismate to isochorismate near equilibrium and lacks IPL activity.

SA biosynthesis and signaling mutants are impaired in establishing systemic acquired resistance triggered by non-host bacteria or PAMPs.

In defense against the oomycete Pythium irregulare, SA and ethylene are required to prevent disease progression but much less so than jasmonic acid.

ICS1 and ICS2 are both plastid-targeted functional isochorismate synthases that contribute to SA and phylloquinone (unequal redundancy); ICS1:GFP localizes to the plastid stroma; ics1 ics2 double mutants reveal an ICS-independent residual SA pathway.

Chilling-induced SA biosynthesis proceeds through cold induction of ICS1 (and its activators CBP60g and SARD1) and configures the low-temperature transcriptome, but does not contribute to freezing tolerance.

SA-deficient sid2 (ics1) and NahG plants show reduced pathogen-triggered cauline leaf abscission; sid2 was the least compromised defense mutant tested.

ICS1 is the chloroplast-localized isochorismate synthase that commits chorismate to the dominant pathogen-induced salicylic acid biosynthetic pathway, contributing ~90% of pathogen-induced SA; de novo ICS1 induction in systemic tissues is required for SAR, and ICS1 is controlled by a multi-layer transcriptional network (SARD1/CBP60g, TGA1/4, H2O2-CHE) and negative regulators (NAC90/61/36, CAMTAs, WRKYs).