Npr1-KO Mouse

Npr1, also known as Nonexpressor of pathogenesis-related genes 1, is a master regulator in plants. It is central to the salicylic acid (SA)-mediated systemic acquired resistance (SAR), a broad-spectrum disease resistance mechanism. NPR1 controls about 90% of SA-dependent transcriptome in Arabidopsis and plays a crucial role in plant survival under biotic and abiotic stresses [2,6].

NPR1 promotes cell survival during the plant immune response by forming salicylic acid-induced NPR1 condensates (SINCs). These SINCs are enriched with stress-response proteins. The transition of NPR1 into condensates is required for the formation of the NPR1-Cullin 3 E3 ligase complex, which ubiquitinates SINC-localized substrates like EDS1 and specific WRKY transcription factors [1]. Also, NPR1 is a SA receptor. SA-bound NPR1 dimer activates transcription by bridging two TGA transcription factor dimers to form an enhanceosome. Moreover, NPR1 functions in plant immunity through forming distinct nuclear and cytoplasmic biomolecular condensates [2,3]. In addition, both NPR1 and NPR3/NPR4 are SA receptors, but they play opposite roles in transcriptional regulation of SA-induced defense gene expression [4]. The perception of SA by NPR1 and NPR4 is needed for the activation of N-hydroxypipecolic acid biosynthesis, which is essential for inducing systemic acquired resistance [5]. High air humidity dampens the SA pathway and NPR1 function, as NPR1 is less ubiquitinated and has lower promoter binding affinity under high humidity [7]. A fungal effector CfEC12 can target the plant SA defense pathway by suppressing the interaction between MdNIMIN2 and MdNPR1, thus promoting fungal infection [8]. Overexpressing NPR1 in transgenic plants can enhance resistance to biotic and abiotic stresses, but may also cause detrimental morphological traits [9].

In summary, NPR1 is a key regulator in plant immunity, mainly through its functions in SA-mediated signaling, transcriptional regulation, and formation of condensates. Understanding NPR1's role helps in developing strategies to engineer plant resistance against biotic and abiotic stresses.