THE ARABIDOPSIS NPR1 GENE THAT CONTROLS SYSTEMIC ACQUIRED-RESISTANCE ENCODES A NOVEL PROTEIN CONTAINING ANKYRIN REPEATS

The Arabidopsis NPR1 gene controls the onset of systemic acquired resi stance (SAR), a plant immunity, to a broad spectrum of pathogens that is normally established after a primary exposure to avirulent pathogen s. Mutants with defects in NPR1 fail to respond to various SAP-inducin g treatments, displaying little expression of pathogenesis-related (PR ) genes and exhibiting increased susceptibility to infections. NPR1 wa s cloned using a map-based approach and was found to encode a novel pr otein containing ankyrin repeats. The lesion in one npr1 mutant allele disrupted the ankyrin consensus sequence, suggesting that these repea ts are important for NPR1 function. Furthermore, transformation of the cloned wild-type NPR1 gene into npr1 mutants not only complemented th e mutations, restoring the responsiveness to SAP induction with respec t to PR-gene expression and resistance to infections, but also rendere d the transgenic plants more resistant to infection by P. syringae in the absence of SAP induction.