No abstract

SummarySalicylic acid (SA) is an essential hormone for plant defence and development. SA NPR1-related genotypes also confirm the pivotal role of NPR1 in SA perception, and suggest an active program of depletion of resources in the infected tissues.

Salicylic acid (SA) is necessary for plant defence against some pathogens, whereas NPR1 is necessary for SA perception. Plant defence can be induced to an extreme by several applications of benzothiadiazole (BTH), an analogue of SA. Thus, plants that do not perceive BTH grow unaffected, whereas wild-type plants grow stunted. This feature allows us to screen for mutants in Arabidopsis thaliana that show insensitivity to BTH in a highthroughput fashion. Most of the mutants are npr1 alleles, with similar phenotypes in plant weight and pathogen growth. The mutations are clustered in the carboxylterminal part of the protein, and no obvious null alleles were recovered. These facts have prompted a search for knockouts in the NPR1 gene. Two of these KO alleles identified are null and have an intermediate phenotype. All the evidence presented lead us to propose a redundancy in SA perception, with the paralogs of NPR1 taking part in this signalling. We show that the mutations recovered in the screening genetically interact with the paralogs preventing their function in SA signalling.