Genetic dissection of systemic acquired resistance

Significant progress has been made in the past year in understanding the me chanism of systemic acquired resistance. Mitogen-activated protein kinase c ascades have been implicated as negative regulators of salicyclic acid accu mulation and the induction of resistance. The salicylic acid signal is tran sduced through NPR1, a nuclear-localized protein that interacts with transc ription factors that are involved in regulating salicylic-acid-mediated gen e expression. Both promoter analyses and genetic studies have shown that ge ne expression in systemic acquired resistance requires not only the activat ion of a transcriptional activator(s) but also inhibition of a transcriptio nal repressor(s). Microarray experiments have been performed to search for those genes whose expression is transcriptionally regulated during systemic acquired resistance and to identify common promoter elements that control these genes.