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Plants and plant pathogens are subject to continuous co-evolutionary pressure for dominance, and the outcomes of these interactions can substantially impact agriculture and food security1-3. In virus- plant interactions, one of the major mechanisms for plant antiviral immunity relies on RNA silencing, which is often suppressed by co-evolving virus suppressors, thus enhancing viral pathogenicity in susceptible hosts1. In addition, plants use the nucleotide-binding and leucine-rich repeat (NB-LRR) domain-containing resistance proteins,which recognize viral effectors to activate effector-triggered immunity in a defence mechanism similar to that employed in nonviral infections2,3. Unlike most eukaryotic organisms, plants are not known to activate mechanisms of host global translation suppression to fight viruses1,2. Here we demonstrate inArabidopsis that the constitutive activation of NIK1, a leucine-rich repeat receptor-like kinase (LRR-RLK) identified as a virulence target of the begomovirus nuclear shuttle protein (NSP)4-6, leads to global translation suppression and translocation of the downstreamcomponent RPL10 to the nucleus, where it interacts with a newly identifiedMYB-like protein, L10-INTERACTING MYB DOMAIN-CONTAINING PROTEIN (LIMYB), to downregulate translational machinery genes fully. LIMYBoverexpression represses ribosomal protein genes at the transcriptional level, resulting in protein synthesis inhibition, decreased viral messenger RNA association with polysome fractions and enhanced tolerance to begomovirus. By contrast, the loss of LIMYB function releases the repression of translation-related genes and increases susceptibility to virus infection. Therefore, LIMYB links immune receptorLRR-RLK activation to global translation suppression as an antiviral immunity strategy in plants.
NIK1 was first identified as a virulence target of the begomovirus NSP5,6. For begomoviruses, a group of single-stranded DNA viruses that infect major crops, the success of infection relies not only on viral suppressors of RNA silencing4 but also on the viral inhibitor, NSP, of the immune receptor, NIK1 (ref. 5). The NIK1 protein belongs to the sameLRR-RLKsubfamily as the well-characterizedPAMPrecognition co-receptor BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1)7,8. NIK1 is involved inplant antiviral immunity5,whereasBAK1is required for plant immunity against bacteria, fungi and oomycetes through its interactions with multiple PAMP-recognition LRR-RLKs9. We have previously demonstrated that the activation of NIK1 kinase is induced by the phosphorylation of Thr 474 within the activation (A)-loop10,11 (Supplementary Discussion 1). Apart from the identification of RPL10 as a downstream effector in NIK1-mediated antiviral immunity12,13, mechanistic knowledge of the signalling pathway is lacking, and the molecular nature of the defence...