NPR1 is a master regulator of plant response to pathogens that confers immunity through a transcriptional cascade mediated by salicylic acid (SA) and the TGA transcription factors. Little is known, however, about its implication in plant response to abiotic stress. Here, we provide genetic and molecular evidence supporting that Arabidopsis NPR1 plays an essential role in cold acclimation by regulating cold-induced gene expression independently of SA and TGA factors.
Our results demonstrate that, in response to low temperature, cytoplasmic NPR1 oligomers release monomers that translocate to the nucleus where they interact with heat shock transcription factors HSFA1 to promote the induction of HSFA1-regulated genes and cold acclimation. As expected, Arabidopsis mutants deficient in HSFA1 factors display reduced capacity to cold acclimate, and cold induction of heat stress-responsive genes is required for correct development of cold acclimation.
All these findings unveil an unexpected function for NPR1 in plant response to low temperature, reveal a new regulatory pathway for cold acclimation mediated by NPR1 and HSFA1 factors, and place NPR1 as a central hub integrating cold and pathogen signaling for a better adaptation of plants to their ever-changing environment.