Figure 8.

Model for disease resistance signal transduction. The dashed line leading from avr/R gene-dependent primary signal to reactive oxygen production is meant to indicate that this pathway is quantitatively much less significant than the cell death-induced reactive oxygen production. SA potentiation of cell death is represented with a symbol for a rheostat. Although pictured as being distinct, “triggering factor” could be nitric oxide, reactive oxygen, both, or something different. The SA-dependent negative feedback loop's precise target is not known. NDR1-independent pathways for SA production discussed in the text are not pictured.