While SAR is established in leaves by initiating FMO1 expression upon a primary infection to produce the NHP signal, which is later attenuated by the induction of the NHP-conjugating UGT76B1, FMO1 and UGT76B1 exhibit a high basal expression level in naïve Arabidopsis roots to synthesize NHP and to concurrently confine its mobility via glucosylation. Here, FMO1 is linked to infection.