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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11847
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Item NIK1-mediated translation suppression functions as a plant antiviral immunity mechanism(Nature, 2015-04-30) Zorzatto, Cristiane; Machado, João Paulo B.; Lopes, Kênia V. G.; Nascimento, Kelly J. T.; Pereira, Welison A.; Brustolini, Otávio J. B.; Reis, Pedro A. B.; Calil, Iara P.; Deguchi, Michihito; Sachetto-Martins, Gilberto; Gouveia, Bianca C.; Loriato, Virgílio A. P.; Silva, Marcos A. C.; Silva, Fabyano F.; Santos, Anésia A.; Chory, Joanne; Fontes, Elizabeth P. B.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 security^ 1–3 . 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 hosts^ 1 . 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 non-viral infections^ 2,3 . Unlike most eukaryotic organisms, plants are not known to activate mechanisms of host global translation suppression to fight viruses^ 1,2 . Here we demonstrate in Arabidopsis 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 downstream component RPL10 to the nucleus, where it interacts with a newly identified MYB-like protein, L10-INTERACTING MYB DOMAIN-CONTAINING PROTEIN (LIMYB), to downregulate translational machinery genes fully. LIMYB overexpression 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 receptor LRR-RLK activation to global translation suppression as an antiviral immunity strategy in plants.Item The ribosomal protein L10/QM-like protein is a component of the NIK-mediated antiviral signaling(Virology, 2008-08-02) Rocha, Carolina S.; Santos, Anésia A.; Machado, João Paulo B.; Fontes, Elizabeth P.B.The NIK (NSP-interacting kinase)-mediated antiviral signaling pathway was identified as a virulence target of the begomovirus nuclear shuttle protein (NSP). Here, we further characterized this layer of plant innate defense by identifying the ribosomal protein L10 (rpL10), a QM-like protein, as a downstream effector of the antiviral signaling. Although both ribosomal proteins rpL10 and rpL18 were found to associate with NIK1 through yeast two-hybrid screening, the NIK receptors specifically phosphorylated rpL10 in vitro. Furthermore, loss of rpL10 function significantly increased susceptibility to begomovirus infection, recapitulating the phenotype of nik knockout lines. Our results genetically linked rpL10 to the NIK-mediated antiviral signaling.Item Translational control in plant antiviral immunity(Genetics and Molecular Biology, 2016-09-27) Machado, João Paulo B.; Iara P., Calil; Santos, Anésia A.; Fontes, Elizabeth P.B.Due to the limited coding capacity of viral genomes, plant viruses depend extensively on the host cell machinery to support the viral life cycle and, thereby, interact with a large number of host proteins during infection. Within this context, as plant viruses do not harbor translation-required components, they have developed several strategies to subvert the host protein synthesis machinery to produce rapidly and efficiently the viral proteins. As a countermeasure against infection, plants have evolved defense mechanisms that impair viral infections. Among them, the host-mediated translational suppression has been characterized as an efficient mean to restrict infection. To specifically suppress translation of viral mRNAs, plants can deploy susceptible recessive resistance genes, which encode translation initiation factors from the eIF4E and eIF4G family and are required for viral mRNA translation and multiplication. Additionally, recent evidence has demonstrated that, alternatively to the cleavage of viral RNA targets, host cells can suppress viral protein translation to silence viral RNA. Finally, a novel strategy of plant antiviral defense based on suppression of host global translation, which is mediated by the transmembrane immune receptor NIK1 (nuclear shuttle protein (NSP)-Interacting Kinase1), is discussed in this review.Item Immune receptors and co-receptors in antiviral innate immunity in plants(Frontiers in Microbiology, 2017-01-05) Gouveia, Bianca C.; Calil, Iara P.; Machado, João Paulo B.; Santos, Anésia A.; Fontes, Elizabeth P. B.Plants respond to pathogens using an innate immune system that is broadly divided into PTI (pathogen-associated molecular pattern- or PAMP-triggered immunity) and ETI (effector-triggered immunity). PTI is activated upon perception of PAMPs, conserved motifs derived from pathogens, by surface membrane-anchored pattern recognition receptors (PRRs). To overcome this first line of defense, pathogens release into plant cells effectors that inhibit PTI and activate effector-triggered susceptibility (ETS). Counteracting this virulence strategy, plant cells synthesize intracellular resistance (R) proteins, which specifically recognize pathogen effectors or avirulence (Avr) factors and activate ETI. These coevolving pathogen virulence strategies and plant resistance mechanisms illustrate evolutionary arms race between pathogen and host, which is integrated into the zigzag model of plant innate immunity. Although antiviral immune concepts have been initially excluded from the zigzag model, recent studies have provided several lines of evidence substantiating the notion that plants deploy the innate immune system to fight viruses in a manner similar to that used for non-viral pathogens. First, most R proteins against viruses so far characterized share structural similarity with antibacterial and antifungal R gene products and elicit typical ETI-based immune responses. Second, virus-derived PAMPs may activate PTI-like responses through immune co-receptors of plant PTI. Finally, and even more compelling, a viral Avr factor that triggers ETI in resistant genotypes has recently been shown to act as a suppressor of PTI, integrating plant viruses into the co-evolutionary model of host-pathogen interactions, the zigzag model. In this review, we summarize these important progresses, focusing on the potential significance of antiviral immune receptors and co-receptors in plant antiviral innate immunity. In light of the innate immune system, we also discuss a newly uncovered layer of antiviral defense that is specific to plant DNA viruses and relies on transmembrane receptor-mediated translational suppression for defense.Item Regulated nuclear trafficking of rpL10A mediated by NIK1 represents a defense strategy of plant cells against virus(Public Library of Science Pathogens, 2008-12-26) Carvalho, Claudine M.; Santos, Anésia A.; Pires, Silvana R.; Rocha, Carolina S.; Saraiva, Daniela I.; Machado, João Paulo B.; Mattos, Eliciane C.; Fietto, Luciano G.; Fontes, Elizabeth P. B.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.