Inactive NPR1/NH1 and SA and Cu2+ activates NPR1/NH1 (NPR1/NH1 modification at Cys 521 and Cys 529)
It must be noted that there are conflicting reports on the validity of the hypothesis that NPR1 protein of Arabidopsis thaliana is a SA receptor, however, in both Arabidopsis and Oryza sativa NPR1 is directly implicated in SA signaling and Systemic Acquired Resistance in plant immunity.