RESUMO
Acidic soils, where aluminum (Al) toxicity is a major agricultural constraint, are globally widespread and are prevalent in developing countries. In sorghum, the root citrate transporter SbMATE confers Al tolerance by protecting root apices from toxic Al3+, but can exhibit reduced expression when introgressed into different lines. We show that allele-specific SbMATE transactivation occurs and is caused by factors located away from SbMATE Using expression-QTL mapping and expression genome-wide association mapping, we establish that SbMATE transcription is controlled in a bipartite fashion, primarily in cis but also in trans Multiallelic promoter transactivation and ChIP analyses demonstrated that intermolecular effects on SbMATE expression arise from a WRKY and a zinc finger-DHHC transcription factor (TF) that bind to and trans-activate the SbMATE promoter. A haplotype analysis in sorghum RILs indicates that the TFs influence SbMATE expression and Al tolerance. Variation in SbMATE expression likely results from changes in tandemly repeated cis sequences flanking a transposable element (a miniature inverted repeat transposable element) insertion in the SbMATE promoter, which are recognized by the Al3+-responsive TFs. According to our model, repeat expansion in Al-tolerant genotypes increases TF recruitment and, hence, SbMATE expression, which is, in turn, lower in Al-sensitive genetic backgrounds as a result of lower TF expression and fewer binding sites. We thus show that even dominant cis regulation of an agronomically important gene can be subjected to precise intermolecular fine-tuning. These concerted cis/trans interactions, which allow the plant to sense and respond to environmental cues, such as Al3+ toxicity, can now be used to increase yields and food security on acidic soils.
Assuntos
Alumínio/toxicidade , Proteínas de Transporte de Ânions/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/efeitos dos fármacos , Sorghum/efeitos dos fármacos , Proteínas de Transporte de Ânions/genética , Cromossomos de Plantas/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Raízes de Plantas/metabolismo , Regiões Promotoras Genéticas/genética , Locos de Características Quantitativas/genética , Sorghum/genética , Sorghum/metabolismo , Sequências de Repetição em Tandem/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Begomoviruses (Geminiviridae family) represent a severe constraint to agriculture worldwide. As ssDNA viruses that replicate in the nuclei of infected cells, the nascent viral DNA has to move to the cytoplasm and then to the adjacent cell to cause disease. The begomovirus nuclear shuttle protein (NSP) assists the intracellular transport of viral DNA from the nucleus to the cytoplasm and cooperates with the movement protein (MP) for the cell-to-cell translocation of viral DNA to uninfected cells. As a facilitator of intra- and intercellular transport of viral DNA, NSP is predicted to associate with host proteins from the nuclear export machinery, the intracytoplasmic active transport system, and the cell-to-cell transport complex. Furthermore, NSP functions as a virulence factor that suppresses antiviral immunity against begomoviruses. In this review, we focus on the protein-protein network that converges on NSP with a high degree of centrality and forms an immune hub against begomoviruses. We also describe the compatible host functions hijacked by NSP to promote the nucleocytoplasmic and intracytoplasmic movement of viral DNA. Finally, we discuss the NSP virulence function as a suppressor of the recently described NSP-interacting kinase 1 (NIK1)-mediated antiviral immunity. Understanding the NSP-host protein-protein interaction (PPI) network will probably pave the way for strategies to generate more durable resistance against begomoviruses.
RESUMO
The Geminiviridae family is one of the most successful and largest families of plant viruses that infect a large variety of important dicotyledonous and monocotyledonous crops and cause significant yield losses worldwide. This broad spectrum of host range is only possible because geminiviruses have evolved sophisticated strategies to overcome the arsenal of antiviral defenses in such diverse plant species. In addition, geminiviruses evolve rapidly through recombination and pseudo-recombination to naturally create a great diversity of virus species with divergent genome sequences giving the virus an advantage over the host recognition system. Therefore, it is not surprising that efficient molecular strategies to combat geminivirus infection under open field conditions have not been fully addressed. In this review, we present the anti-geminiviral arsenal of plant defenses, the evolved virulence strategies of geminiviruses to overcome these plant defenses and the most recent strategies that have been engineered for transgenic resistance. Although, the in vitro reactivation of suppressed natural defenses as well as the use of RNAi and CRISPR/Cas systems hold the potential for achieving broad-range resistance and/or immunity, potential drawbacks have been associated with each case.
Assuntos
Sistemas CRISPR-Cas , Geminiviridae/fisiologia , Interações Hospedeiro-Patógeno , Doenças das Plantas/imunologia , Imunidade Vegetal/genética , Interferência de RNA , Produtos Agrícolas/genética , Produtos Agrícolas/imunologia , Resistência à Doença/genética , Engenharia Genética , Doenças das Plantas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/imunologiaRESUMO
Plants deploy various immune receptors to recognize pathogens and defend themselves. Crosstalk may happen among receptor-mediated signal transduction pathways in the same host during simultaneous infection of different pathogens. However, the related function of the receptor-like kinases (RLKs) in thwarting different pathogens remains elusive. Here, we report that NIK1, which positively regulates plant antiviral immunity, acts as an important negative regulator of antibacterial immunity. nik1 plants exhibit dwarfed morphology, enhanced disease resistance to bacteria and increased PAMP-triggered immunity (PTI) responses, which are restored by NIK1 reintroduction. Additionally, NIK1 negatively regulates the formation of the FLS2/BAK1 complex. The interaction between NIK1 and FLS2/BAK1 is enhanced upon flg22 perception, revealing a novel PTI regulatory mechanism by an RLK. Furthermore, flg22 perception induces NIK1 and RPL10A phosphorylation in vivo, activating antiviral signalling. The NIK1-mediated inverse modulation of antiviral and antibacterial immunity may allow bacteria and viruses to activate host immune responses against each other.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Imunidade Vegetal/genética , Proteínas Quinases/genética , Proteínas Serina-Treonina Quinases/genética , Arabidopsis/microbiologia , Arabidopsis/virologia , Proteínas de Arabidopsis/imunologia , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas/imunologia , Interações Hospedeiro-Patógeno/imunologia , Complexos Multiproteicos/imunologia , Complexos Multiproteicos/metabolismo , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Doenças das Plantas/virologia , Imunidade Vegetal/imunologia , Vírus de Plantas/imunologia , Vírus de Plantas/fisiologia , Plantas Geneticamente Modificadas , Ligação Proteica , Proteínas Quinases/imunologia , Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/imunologia , Proteínas Serina-Treonina Quinases/metabolismo , Pseudomonas syringae/imunologia , Pseudomonas syringae/fisiologia , Transdução de Sinais/genética , Transdução de Sinais/imunologiaRESUMO
The bipartite begomoviruses (Geminiviridae family), which are DNA viruses that replicate in the nucleus of infected cells, encode the nuclear shuttle protein (NSP) to facilitate the translocation of viral DNA from the nucleus to the cytoplasm via nuclear pores. This intracellular trafficking of NSP-DNA complexes is accessorized by the NSP-interacting guanosine triphosphatase (NIG) at the cytosolic side. Here, we report the nuclear redistribution of NIG by AtWWP1, a WW domain-containing protein that forms immune nuclear bodies (NBs) against begomoviruses. We demonstrated that AtWWP1 relocates NIG from the cytoplasm to the nucleus where it is confined to AtWWP1-NBs, suggesting that the NIG-AtWWP1 interaction may interfere with the NIG pro-viral function associated with its cytosolic localization. Consistent with this assumption, loss of AtWWP1 function cuased plants more susceptible to begomovirus infection, whereas overexpression of AtWWP1 enhanced plant resistance to begomovirus. Furthermore, we found that a mutant version of AtWWP1 defective for NB formation was no longer capable of interacting with and relocating NIG to the nucleus and lost its immune function against begomovirus. The antiviral function of AtWWP1-NBs, however, could be antagonized by viral infection that induced either the disruption or a decrease in the number of AtWWP1-NBs. Collectively, these results led us to propose that AtWWP1 organizes nuclear structures into nuclear foci, which provide intrinsic immunity against begomovirus infection.
Assuntos
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Begomovirus/fisiologia , Núcleo Celular/metabolismo , Domínios WW , Arabidopsis/citologia , Arabidopsis/imunologia , Arabidopsis/metabolismo , Arabidopsis/virologia , Citosol/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Multimerização Proteica , Transporte ProteicoRESUMO
Lectins are involved in a wide range of biological mechanisms, like immunomodulatory agent able to activate the innate immunity. In this study, we purified and characterized a new lectin from cauliflower (Brassica oleracea ssp. botrytis - BOL) by three sequential chromatographic steps and confirmed the purity by SDS-PAGE. Additionally, we evaluated the role of the lectin in innate immunity by a phagocytosis assay, production of H2O2 and NO. BOL was characterized like a non-glycosylated protein that showed a molecular mass of â¼34kDa in SDS-PAGE. Its N-terminal sequence (ETRAFREERPSSKIVTIAG) did not reveal any similarity to the other lectins; nevertheless, it showed 100% homology to a putative TRAF-like protein from Brassica rapa and Brassica napus. This is a first report of the TRAF-protein with lectinic activity. The BOL retained its complete hemagglutination activity from 4°C up to 60°C, with stability being more apparent between pH 7.0 and 8.0. Moreover, the lectin was able to stimulate phagocytosis and induce the production of H2O2 and NO. Therefore, BOL can be explored as an immunomodulatory agent by being able to activate the innate immunity and favor antigen removal.