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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 Sustained NIK-mediated antiviral signalling confers broad-spectrum tolerance to begomoviruses in cultivated plants(Plant Biotechnology Journal, 2015-01-06) Brustolini, Otávio J.B.; Machado, Joao Paulo B.; Condori-Apfata, Jorge A.; Coco, Daniela; Deguchi, Michihito; Loriato, Virgílio A.P.; Pereira, Welison A.; Alfenas-Zerbini, Poliane; Zerbini, Francisco M.; Inoue-Nagata, Alice K.; Santos, Anesia A.; Chory, Joanne; Silva, Fabyano F.; Fontes, Elizabeth P.B.Begomovirus-associated epidemics currently threaten tomato production worldwide due to the emergence of highly pathogenic virus species and the proliferation of a whitefly B biotype vector that is adapted to tomato. To generate an efficient defence against begomovirus, we modulated the activity of the immune defence receptor nuclear shuttle protein (NSP)-interacting kinase (NIK) in tomato plants; NIK is a virulence target of the begomovirus NSP during infection. Mutation of T474 within the kinase activation loop promoted the constitutive activation of NIK-mediated defences, resulting in the down-regulation of translation-related genes and the suppression of global translation. Consistent with these findings, transgenic lines harbouring an activating mutation (T474D) were tolerant to the tomato-infecting begomoviruses ToYSV and ToSRV. This phenotype was associated with reduced loading of coat protein viral mRNA in actively translating polysomes, lower infection efficiency and reduced accumulation of viral DNA in systemic leaves. Our results also add some relevant insights into the mechanism underlying the NIK-mediated defence. We observed that the mock-inoculated T474D-overexpressing lines showed a constitutively infected wild-type transcriptome, indicating that the activation of the NIK- mediated signalling pathway triggers a typical response to begomovirus infection. In addition, the gain-of-function mutant T474D could sustain an activated NIK-mediated antiviral response in the absence of the virus, further confirming that phosphorylation of Thr-474 is the crucial event that leads to the activation of the kinase.Item Cryptochromes interact directly with PIFs to control plant growth in limiting blue light(Cell Press, 2015-12-24) Pedmale, Ullas V.; Huang, Shao-shan Carol; Zander, Mark; Cole, Benjamin J.; Hetzel, Jonathan; Ljung, Karin; Reis, Pedro A.B.; Sridevi, Priya; Nito, Kazumasa; Nery, Joseph R.; Ecker, Joseph R.; Chory, JoanneSun-loving plants have the ability to detect and avoid shading through sensing of both blue and red light wavelengths. Higher plant cryptochromes (CRYs) control how plants modulate growth in response to changes in blue light. For growth under a canopy, where blue light is diminished, CRY1 and CRY2 perceive this change and respond by directly contacting two bHLH transcription factors, PIF4 and PIF5. These factors are also known to be controlled by phytochromes, the red/far-red photoreceptors; however, transcriptome analyses indicate that the gene regulatory programs induced by the different light wavelengths are distinct. Our results indicate that CRYs signal by modulating PIF activity genome wide and that these factors integrate binding of different plant photoreceptors to facilitate growth changes under different light conditions.