Regulated nuclear trafficking of rpL10A mediated by NIK1 represents a defense strategy of plant cells against virus.
The NSP-interacting kinase (NIK) receptor-mediated defense pathway has been identified recently as a virulence target of the geminivirus nuclear shuttle protein (NSP). However, the NIK1-NSP interaction does not fit into the elicitor-receptor model of resistance, and hence the molecular mechanism that links this antiviral response to receptor activation remains obscure. Here, we identified a ribosomal protein, rpL10A, as a specific partner and substrate of NIK1 that functions as an immediate downstream effector of NIK1-mediated response. Phosphorylation of cytosolic rpL10A by NIK1 redirects the protein to the nucleus where it may act to modulate viral infection. While ectopic expression of normal NIK1 or a hyperactive NIK1 mutant promotes the accumulation of phosphorylated rpL10A within the nuclei, an inactive NIK1 mutant fails to redirect the protein to the nuclei of co-transfected cells. Likewise, a mutant rpL10A defective for NIK1 phosphorylation is not redirected to the nucleus. Furthermore, loss of rpL10A function enhances susceptibility to geminivirus infection, resembling the phenotype of nik1 null alleles. We also provide evidence that geminivirus infection directly interferes with NIK1-mediated nuclear relocalization of rpL10A as a counterdefensive measure. However, the NIK1-mediated defense signaling neither activates RNA silencing nor promotes a hypersensitive response but inhibits plant growth and development. Although the virulence function of the particular geminivirus NSP studied here overcomes this layer of defense in Arabidopsis, the NIK1-mediated signaling response may be involved in restricting the host range of other viruses.
Carvalho
Claudine M
CM
Departamento de Bioquímica e Biologia Molecular, BIOAGRO, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Santos
Anésia A
AA
Pires
Silvana R
SR
Rocha
Carolina S
CS
Saraiva
Daniela I
DI
Machado
João Paulo B
JP
Mattos
Eliciane C
EC
Fietto
Luciano G
LG
Fontes
Elizabeth P B
EP
D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D053839:Begomovirus / Q000276:immunology; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D017791:Geminiviridae / Q000276:immunology; D007113:Immunity, Innate / Q000502:physiology*; D018551:Solanum lycopersicum / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D010935:Plant Diseases / Q000276:immunology / Q000821:virology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010942:Plant Viruses / Q000276:immunology*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport; D000080882:Ribosomal Protein L10; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D013379:Substrate Specificity; D014162:Transfection
D029681:Arabidopsis Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; C000630687:RPL10A protein, Arabidopsis; D012269:Ribosomal Proteins; C000630691:ribosomal protein L10, Arabidopsis; C000597753:NIK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases