Pipped at the Post: Pipecolic Acid Derivative Identified as SAR Regulator.

The non-protein amino acid pipecolic acid (Pip) is a lysine catabolite involved in plant systemic acquired resistance (SAR). In this issue of Cell, Hartmann et al. (2018) demonstrate that a flavin-dependent monooxygenase converts Pip to N-hydroxypipecolic acid (NHP), which functions as a critical metabolic regulator of SAR in Arabidopsis.