Characterization of an Arabidopsis Mutant That Is Nonresponsive to Inducers of Systemic Acquired Resistance.

Abstract

Systemic acquired resistance (SAR) is a general defense response in plants that is characterized by the expression of pathogenesis-related (PR) genes. SAR can be induced after a hypersensitive response to an avirulent pathogen or by treatment with either salicylic acid (SA) or 2,6-dichloroisonicotinic acid (INA). To dissect the signal transduction pathway of SAR, we isolated an Arabidopsis mutant that lacks the expression of an SA-, INA-, and pathogen-responsive chimeric reporter gene composed of the 5[prime] untranslated region of an Arabidopsis PR gene, [beta]-1,3-glucanase (BGL2), and the coding region of [beta]-glucuronidase (GUS). This mutant, npr1 (nonexpresser of PR genes), carries a single recessive mutation that abolishes the SAR-responsive expression of other PR genes as well. While SA-, INA-, or avirulent pathogen-induced SAR protects wild-type plants from Pseudomonas syringae infection, the mutant cannot be protected by pretreatment with these inducers. The insensitivity of npr1 to SA, INA, and avirulent pathogens in SAR induction indicates that these inducers share a common signal transduction pathway. Moreover, in npr1, the localized expression of PR genes induced by a virulent Pseudomonas pathogen is disrupted, and the lesion formed is less confined. These results suggest a role for PR genes in preventing the proximal spread of pathogens in addition to their suggested role in SAR.

The novel elicitor AsES triggers a defense response against Botrytis cinerea in Arabidopsis thaliana

“…Plants were grown during 4 weeks in a 12 h light/12 h dark cycle with 60-70% of relative humidity, with a day temperature of 20-22 • C and a night temperature of 16-18 • C. A. thaliana ecotype Columbia-0 (Col-0) wild-type plants were obtained from the Nottingham Arabidopsis Stock Centre (Nottingham, UK), transgenic seeds over-expressing the salicylate hydroxylase NahG gene were obtained from J. Ryals [23]. The following A. thaliana mutants (all in the Col-0 background) were used and previously described: jar1-1, coi1-16, etr1-1, ein2-1 [24], ics1 [25], npr1 [26], and dde2.1 [27].…”

Biosynthesis and emission of insect-induced methyl salicylate and methyl benzoate from rice

“…NH1 is the ortholog of Arabidopsis NPR1, is a key regulator of the SA-mediated systemic acquired resistance (SAR) [4,35]. NPR1 encodes a novel protein with a bipartite nuclear localization sequence.…”

OsWRKY03, a rice transcriptional activator that functions in defense signaling pathway upstream of OsNPR1

“…More than a decade ago, additional components downstream of signaling molecules SA, JA and ethylene were characterized in several mutant plants, such as the jasmonate response mutant jar [26], the ethylene response mutant etr [27] and the SAR regulatory mutant npr1 [28]. In a genetic screening for plants failed to express PR genes after SAR induction, npr1 mutant was isolated in Arabidopsis [28] and NPR1 gene was cloned [29].…”

“…In a genetic screening for plants failed to express PR genes after SAR induction, npr1 mutant was isolated in Arabidopsis [28] and NPR1 gene was cloned [29]. Further results revealed that NPR1 was a key regulator of SA-mediated SAR in Arabidopsis [30][31][32].…”