Open AccessNONEXPRESSOR OF PATHOGENESIS‐RELATED PROTEINS1 (NPR1) and some NPR1‐related proteins are sensitive to salicylic acid
Author(s) -
MAIER FELIX,
ZWICKER SYLVIA,
HÜCKELHOVEN ANGELA,
MEISSNER MEIKE,
FUNK JENNIFER,
PFITZNER ARTUR J. P.,
PFITZNER URSULA M.
Publication year - 2011
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1111/j.1364-3703.2010.00653.x
Subject(s) - salicylic acid , npr1 , biology , pathogenesis , botany , biochemistry , immunology , medicine , natriuretic peptide , heart failure
SUMMARY NONEXPRESSOR OF PATHOGENESIS‐RELATED PROTEINS1 (NPR1; also known as NIM1) is a master regulator of systemic acquired resistance (SAR). SAR is induced by salicylic acid (SA), leading to the expression of PATHOGENESIS‐RELATED (PR) genes. Current evidence suggests that NPR1 is part of a transcription complex tethered to activation sequence‐1 ( as‐1 )‐like cis ‐acting elements in PR‐1 gene promoters through TGA transcription factors, and that SA‐dependent PR‐1 gene expression is regulated by NIM1‐INTERACTING (NIMIN) proteins. In Arabidopsis, NPR1 is active only after SA induction. Regulation of Arabidopsis NPR1 activity has been proposed to comprise cysteine‐156 (Cys‐156), mediating SA‐induced cytoplasmic oligomer–nuclear monomer exchange, and Cys‐521 and Cys‐529, mediating SA‐dependent transcriptional activation. Tobacco NPR1 does not harbour these residues. To understand the function of tobacco NPR1, we analysed its biochemical capabilities in a heterologous system: yeast. Tobacco NPR1 differs from Arabidopsis NPR1 in its subcellular localization and its transactivation potential. Yet, both tobacco and Arabidopsis NPR1, as well as tobacco NIM1‐like1, alter some of their biochemical activities in response to SA. Whereas the addition of SA to yeast growth medium induces transcriptional activity in tobacco NPR1, its interaction with NIMIN2‐type proteins is suppressed. The effects of SA are specific, sensitive and occur coordinately. They are abolished completely by mutation of the arginine residue within the invariable penta‐amino acid motif LENRV, as present in the nonfunctional Arabidopsis nim1‐4 allele. Furthermore, NPR1 proteins with the LENRV domain coincidently harbour a broad and strongly conserved NIMIN1/NIMIN2 binding site. Our data suggest that NPR1 and some NPR1‐like proteins are sensitive to the plant hormone SA, altering some of their biochemical capabilities to enable stimulus‐dependent gene expression. The sensitivity of NPR1 proteins to SA, together with their differential interaction with diverse NIMIN proteins, seems a plausible molecular basis for the timely and coordinated activation of PR genes during SAR.