The SA pathway is typically activated
in response to pathogens and mediates a hypersensitive
response and the production of an array of
antimicrobial phytoalexins and pathogenesis-related proteins that results in systemic acquired resistance to
a broad spectrum of pathogens (Durrant and Dong,
2004). However, the categorization of JA as an herbivore
defense signal and SA as a pathogen defense
signal is imperfect, as JA-mediated defenses are induced
by some pathogens and SA-mediated defenses
by some herbivores (Moran and Thompson, 2001;
Glazebrook, 2005).