PIP and infection: In the most studied Arabidopsis accession, Col-0, the basal levels of the SAR-associated metabolites SA, Pip, and NHP are generally low (SA, Pip) or undetectable (NHP) in unstressed plants, and rise strongly during the course of infection with P. syringae in both locally inoculated and distal systemic leaf tissue (Hartmann and Zeier, 2019).