Figure 6.

Balance model of wound-induced NO- and redox-signaling in the EFP. Under non-stress conditions low levels of O₂- levels are maintained by the antioxidant system. Basal NO production in the EFP causes protein S-nitrosylation. Local leaf wounding triggers a systemic inhibition of the antioxidant system. Subsequent simultaneous accumulation of O${}_2^{-}$ and NO facilitates ONOO⁻ formation and tyrosine nitration. Hence tyrosine nitration is an indirect evidence for both O${}_2^{-}$ as well as NO synthesis within the pumpkin EFP. O${}_2^{-}$ has a very high affinity for NO. Therefore, tyrosine nitration is favored over S-nitrosylation after wound-induced O${}_2^{-}$ accumulation. SNO, S-nitrosothiols; nTyr, nitrotyrosine.