Untitled

Abstract

NPR1/NIM1 is a key regulator of systemic acquired resistance (SAR) in Arabidopsis. Using the yeast two-hybrid system, we have identified three novel genes, NIMIN-1, NIMIN-2 and NIMIN-3 (NIMIN for NIM1-interacting) that encode structurally related proteins interacting physically with NPR1/NIM1. NIMIN-1 and NIMIN-2 both bind strongly to NPR1/NIM1 via a common binding motif interacting with the C-terminal moiety of NPR1/NIM1, whereas NIMIN-3 interacts with NPR1/NIM1 via the N-terminal part of NPR1/NIM1. In addition, NIMIN-1, NIMIN-2, and NIMIN-3 are able to interact via NPR1/NIM1 with basic leucine zipper transcription factors of the TGA family in a yeast tri-hybrid system. A mutant protein of NPR1/NIM1, npr1-2, which has been shown to be severely impaired in induction of SAR gene expression, failed to bind the NIMIN proteins. The NIMIN genes are expressed in Arabidopsis plants in response to SAR-inducing treatments, and the NIMIN proteins, like NPR1/NIM1, carry functional nuclear localization signals as revealed by expression of fusion proteins in yeast and in transgenic plants. Taken together, these data indicate that the NIMIN proteins, via physical interaction with NPR1/NIM1, are part of the signal transduction pathway leading to SAR gene expression in Arabidopsis.

Posttranslational Modifications of the Master Transcriptional Regulator NPR1 Enable Dynamic but Tight Control of Plant Immune Responses

“…Since NIMIN2 interacts with the N-terminal half of NPR1 while NIMIN1 and NIMIN3 bind to the C-terminal of NPR1 (Weigel et al, 2001), the sustained binding activities of npr1 sim3 to the NIMINs suggest that the sim3 mutation does not significantly perturb protein structure. In parallel, we found that npr1 sim3 has a dominant-negative effect on resistance when crossed into Col-0 (Figure S5B), indicating that the mutant has maintained the right structure to compete with endogenous NPR1.…”

“…In both scenarios, it is not known whether and how NPR1 interactions with TFs are regulated in plants. In yeast two-hybrid analysis, however, NPR1 has been shown to interact with TGA and NIMIN (NIM1-INTERACTING) TFs constitutively (Despres et al, 2000; Weigel et al, 2001; Zhang et al, 1999; Zhou et al, 2000), with the exception of TGA1 and TGA4 (Despres et al, 2003). …”

Development of disease-resistant rice using regulatory components of induced disease resistance

“…Members of the WRKY TF family also act downstream of NPR1 (Wang et al, 2006). A negative regulator of NPR1, NIM1-INTERACTING1 (NIMIN1), antagonizes the NPR1-dependent SA pathway by binding to NPR1 (Weigel et al, 2001, 2005). Arabidopsis also has an SA-dependent but NPR1-independent signaling pathway(s), which operates during the early phase of SA pathway activation (Li et al, 2004; Uquillas et al, 2004; Blanco et al, 2005).…”

“…OsNPR1/NH1 interacts with b-ZIP-type TGA TFs to regulate SA-responsive genes (Fitzgerald et al, 2005). OsNPR1/NH1 function was repressed by direct interaction with negative regulator of disease resistance (NRR; Chern et al, 2005a), a homolog of Arabidopsis NIMIN (Weigel et al, 2001, 2005). These results suggest that post-translational regulation and action mode of NPR1 proteins is conserved between Arabidopsis and rice, with an exception of their proteasome degradation (see below).…”

Interaction specificity and coexpression of rice NPR1 homologs 1 and 3 (NH1 and NH3), TGA transcription factors and Negative Regulator of Resistance (NRR) proteins

“…These proteins, named NIMIN1, NIMIN2 and NIMIN3, share very limited sequence similarity but all carry an NPR1-interaction domain [33]. Over-expression of NIMIN1 in Arabidopsis compromises SAR, while knockout and RNA-silencing of NIMIN1 results in enhanced PR-1 gene expression after SA treatment, indicating that NIMIN1 is a suppressor of SAR [34].…”