Active oxygen species in the induction of plant systemic acquired resistance by salicylic acid

A complementary DNA encoding a salicylic acid (SA)--binding protein has been cloned. Its properties suggest involvement in SA-mediated induction of systemic acquired resistance (SAR) in plants. The sequence of the protein is similar to that of catalases and the protein exhibits catalase activity. Salicylic acid specifically inhibited the catalase activity in vitro and induced an increase in [H.sub.2][O.sub.2] concentrations in vivo. [H.sub.2][O.sub.2] or compounds, such as SA, that inhibit catalases or enhance the generation of [H.sub.2][O.sub.2], induced expression of defense-related genes associated with SAR. Thus, the action of SA in SAR is likely mediated by elevated amounts of [H.sub.2][O.sub.2].
Infection of plants, particularly by necrotizing pathogens, leads to enhanced resistance to subsequent attacks by the same or even unrelated pathogens (1). This phenomenon is referred to as systemic acquired [...]