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Positive and Negative Regulation of Salicylic Acid-Dependent Cell Death and Pathogen Resistance in Arabidopsis lsd6 and ssi1 Mutants

August 2000 , Volume 13 , Number  8
Pages  877 - 881

Jean T. Greenberg

The University of Chicago, 1103 East 57th Street EBC410, Chicago, IL 60637, U.S.A.

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Accepted 10 April 2000.

Salicylic acid (SA) is a key defense molecule in higher plants that is required for resistance to diverse pathogens. A number of mutants of Arabidopsis with elevated resistance to pathogens and constitutive activation of defenserelated genes and cell death have been shown to require SA for all of their phenotypes. These mutants potentially identify interesting regulatory genes that control diverse SA responses. When dominant mutations confer SA-dependent phenotypes, it is important to know the genetic basis of dominance in order to draw conclusions on the possible mechanisms of action of the genes identified. Here I characterize the basis of the dominant phenotypes conferred by the ssi1 and lsd6 mutations. I show that ssi1 is haploinsufficient, while lsd6 is a gain-of-function mutation. Thus, SA-dependent responses are under both negative and positive regulation.

Additional keywords: defense responses, P. syringae, triploid.

© 2000 The American Phytopathological Society