Structural basis of NPR1 in activating plant immunity

Article

关键词: CRYO-EM;    COACTIVATOR NPR1;    ANKYRIN REPEAT;    PROTEIN;    MUTANT;    NONEXPRESSOR;    EXPRESSION;    INSIGHTS;    INDUCERS;    FAMILY;   

DOI  :  10.1038/s41586-022-04699-w

来源: SCIE

【 摘 要 】

NPR1 is a master regulator ofthe defence transcriptome induced by the plant immune signal salicylic acid(1-4). Despite the important role of NPR1 in plant immunity(5-7), understanding of its regulatory mechanisms has been hindered by a lack of structural information. Here we report cryo-electron microscopy and crystal structures of Arabidopsis NPR1 and its complex with the transcription factor TGA3. Cryo-electron microscopy analysis reveals that NPR1 is a bird-shaped homodimer comprising a central Broad-complex, Tramtrack and Bric-a-brac (BTB) domain, a BTB and carboxyterminal Kelch helix bundle, four ankyrin repeats and a disordered salicylic-acid-binding domain. Crystal structure analysis reveals a unique zinc-finger motif in BTB for interacting with ankyrin repeats and mediating NPR1 oligomerization. We found that, after stimulation, salicylic-acid-induced folding and docking ofthe salicylic-acid-binding domain onto ankyrin repeats is required for the transcriptional cofactor activity of NPR1, providing a structural explanation for a direct role of salicylic acid in regulating NPR1-dependent gene expression. Moreover, our structure ofthe TGA3(2)-NPR1(2)-TGA3, complex, DNA-binding assay and genetic data showthat dimeric NPR1 activatestranscription by bridging two fatty-acid-bound TGA3 dimersto form an enhanceosome. The stepwise assembly of the NPR1-TGA complex suggests possible hetero-oligomeric complex formation with other transcription factors, revealing how NPR1 reprogramsthe defence transcriptome.

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