Proxitome profiling reveals a conserved SGT1- NSL1 signaling module that activates NLRmediated immunity

Suppressor of G2 allele of skp1(SGT1)is a highly conserved eukaryotic protein that plays a vital role in growth,development,and immunity in both animals and plants.Although some SGT1 interactors have been identified,the molecular regulatory network of SGT1 remains unclear.SGT1 serves as a co-chaperone to stabilize protein complexes such as the nucleotide-binding leucine-rich repeat(NLR)class of immune receptors,thereby positively regulating plant immunity.SGT1 has also been found to be asso-ciated with the SKP1-Cullin-F-box(SCF)E3 ubiquitin ligase complex.However,whether SGT1 targets im-mune repressors to coordinate plant immune activation remains elusive.In this study,we constructed a toolbox for TurbolD-and split-TurbolD-based proximity labeling(PL)assays in Nicotiana benthamiana and used the PL toolbox to explore the SGT1 interactome during pre-and post-immune activation.The comprehensive SGT1 interactome network we identified highlights a dynamic shift from proteins associ-ated with plant development to those linked with plant immune responses.We found that SGT1 interacts with Necrotic Spotted Lesion1(NSL1),which negatively regulates salicylic acid-mediated defenseby inter-fering with the nucleocytoplasmic trafficking of non-expressor of pathogenesis-related genes 1(NPR1)during N NLR-mediated response to tobacco mosaic virus.SGT1 promotes the SCF-dependent degrada-tion of NSL1 to facilitate immune activation,while salicylate-induced protein kinase-mediated phosphory-lation of SGT1further potentiates this process.Besides NNLR,NSL1also functions in several other NLR-mediated immunity.Collectively,our study unveils the regulatory landscape of SGT1 and reveals a novel SGT1-NSL1 signaling module that orchestrates plant innate immunity.

Proximity labeling: an emerging tool for probing in planta molecular interactions

Protein–protein interaction(PPI)networks are key to nearly all aspects of cellular activity.Therefore,the identification of PPIs is important for understanding a specific biological process in an organism.Compared with conventional methods for probing PPIs,the recently described proximity labeling(PL)approach combined with mass spectrometry(MS)-based quantitative proteomics hasemerged as apowerful approach for characterizing PPIs.However,the application of PL in planta remains in its infancy.Here,we summarize recent progress in PL and its potential utilization in plant biology.We specifically summarize advances in PL,including the development and comparison of different PL enzymes and the application of PL for deciphering various molecular interactions in different organisms with an emphasis on plant systems.