The Arabidopsis NIM1 protein shows homology to the mammalian transcription factor inhibitor I kappa B.

Abstract

The NlM7 (for noninducible hmunity) gene product is involved in the signal transduction cascade leading to both systemic acquired resistance (SAR) and gene-for-gene disease resistance in Arabidopsis. We have isolated and characterized five new alleles of nim7 that show a range of phenotypes from weakly impaired in chemically induced pathogenesis-related protein-1 gene expression and funga1 resistance to very strongly blocked. We have isolated the NlM7 gene by using a map-based cloning procedure. Interestingly, the NlMl protein shows sequence homology to the mammalian signal transduction factor IKB subclass (Y. NF-KB/IKB signaling pathways are implicated in disease resistance responses in a range of organisms from Drosophila to mammals, suggesting that the SAR signaling pathway in plants is representative of an ancient and ubiquitous defense mechanism in higher organisms.

Ubiquitination-mediated protein degradation and modification: an emerging theme in plant-microbe interactions

“…SON1 is another F-box protein that has been implicated in plant defense signaling [58]. The son1 (suppressor of nim1-1) mutant was isolated from genetic screens for suppressors of non-inducible immunity1 (nim1, also referred as npr1), of which the corresponding wild-type gene is a key positive regulator of Arabidopsis SAR [59,60]. The son1 mutant displays SAR-independent, constitutive resistance against both the virulent oomycete Peronospora parasitica and the bacterial pathogen Pseudomonas syringae pv tomato strain DC3000, indicating that SON1-mediated ubiquitination negatively regulate plant defense.…”

Salicylic acid-independent plant defence pathways

“…3). Thus, the regulatory factor NPR1 (also called NIM1) 47 is not only required for the SA-dependent expression of PR genes that are activated during SAR, but also for the jasmonate-and ethylenedependent activation of so far unidentified defence responses resulting from rhizobacteria-mediated ISR.…”

“…PR genes are activated in the SAR pathway but not in the ISR pathway, which suggests that the associated defence responses are differentially regulated by NPR1 depending on the signalling pathway that is activated upstream of NPR1. Sequence analysis revealed that NPR1 contains a functionally important ankyrin-repeat domain that might be involved in protein-protein interactions 47,48 . Binding of pathway-specific proteins to NPR1 might therefore account for the separation of the SAR and ISR pathways downstream of NPR1.…”

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

“…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].…”

“…Further results revealed that NPR1 was a key regulator of SA-mediated SAR in Arabidopsis [30][31][32]. Arabidopsis NPR1/NIM1 gene encodes a novel protein with ankyrin repeats [29], which is essential for NPR1 binding to the TGA basic leucine zipper transcription factors [33]. The interaction between NPR1 and TGA factors facilitates the binding of TGA proteins to the SA-responsive as-1 or as-1-like promoter elements, and leads to the activation of downstream genes during defense response [34,35].…”