The Arabidopsis NPR1 protein is a receptor for the plant defense hormone salicylic acid.
Salicylic acid (SA) is an essential hormone in plant immunity, but its receptor has remained elusive for decades. The transcriptional coregulator NPR1 is central to the activation of SA-dependent defense genes, and we previously found that Cys(521) and Cys(529) of Arabidopsis NPR1's transactivation domain are critical for coactivator function. Here, we demonstrate that NPR1 directly binds SA, but not inactive structural analogs, with an affinity similar to that of other hormone-receptor interactions and consistent with in vivo Arabidopsis SA concentrations. Binding of SA occurs through Cys(521/529) via the transition metal copper. Mechanistically, our results suggest that binding of SA causes a conformational change in NPR1 that is accompanied by the release of the C-terminal transactivation domain from the N-terminal autoinhibitory BTB/POZ domain. While NPR1 is already known as a link between the SA signaling molecule and defense-gene activation, we now show that NPR1 is the receptor for SA.
Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada L2S 3A1.
Yue
Y
Wu
Di
D
Zhang
Jee Yan
JY
Chu
Patrick
P
Boyle
Yong
Y
Wang
Ian D
ID
Brindle
Vincenzo
V
De Luca
Charles
C
Després
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D003300:Copper / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism* / Q000494:pharmacology; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics
D029681:Arabidopsis Proteins; D050505:Mutant Proteins; C105496:NPR1 protein, Arabidopsis; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; D003300:Copper; D003545:Cysteine; D020156:Salicylic Acid