OUTSIDE OF CELL Pathogen Elicitor(product of an avr gene) Cell wall 0,-, Reactive oxyge Cell wall species cross-linking NADPH oxidase Plasma membrane Receptor Ion fluxes (R gene Activation of genes for change in roduct Hypersensitive response membrane otential-> Phytoalexin biosynthesis Lignin biosynthesis Systemic Salicylic acid biosynthesis-+acquired Biosynthesis of hydrolytic resistance CYTOPLASM enzymes Figure 13-9 FIGURE 13.25 Many modes of antipathogen defense are induced by infection Fragments of pathogen molecules called elicitors initiate a complex signaling path way leading to the activation of defensive responses. Some bacterial protein elici tors are injected directly into the cell, where they interact with R gene productsFigure 13-9