NHP biosynthesis at infection sites follows a three-step pathway: AGD2-LIKE DEFENSE RESPONSE PROTEIN 1 (ALD1) converts L-lysine to dehydropipecolic acid, SAR DEFICIENT 4 (SARD4) reduces it to pipecolic acid (Pip), and FLAVIN-DEPENDENT MONOOXYGENASE 1 (FMO1) converts Pip to NHP [30,31]. This evidence concerns the gene PIP and infection.