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Andrade MDO, da Silva JC, Soprano AS, Shimo HM, Leme AFP, Benedetti CE. Suppression of citrus canker disease mediated by flagellin perception. Mol Plant Pathol 2023; 24:331-345. [PMID: 36691963 PMCID: PMC10013774 DOI: 10.1111/mpp.13300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 01/05/2023] [Accepted: 01/11/2023] [Indexed: 06/17/2023]
Abstract
Citrus cancer, caused by strains of Xanthomonas citri (Xc) and Xanthomonas aurantifolii (Xa), is one of the most economically important citrus diseases. Although our understanding of the molecular mechanisms underlying citrus canker development has advanced remarkably in recent years, exactly how citrus plants fight against these pathogens remains largely unclear. Using a Xa pathotype C strain that infects Mexican lime only and sweet oranges as a pathosystem to study the immune response triggered by this bacterium in these hosts, we herein report that the Xa flagellin C protein (XaFliC) acts as a potent defence elicitor in sweet oranges. Just as Xa blocked canker formation when coinfiltrated with Xc in sweet orange leaves, two polymorphic XaFliC peptides designated flgIII-20 and flgIII-27, not related to flg22 or flgII-28 but found in many Xanthomonas species, were sufficient to protect sweet orange plants from Xc infection. Accordingly, ectopic expression of XaFliC in a Xc FliC-defective mutant completely abolished the ability of this mutant to grow and cause canker in sweet orange but not Mexican lime plants. Because XaFliC and flgIII-27 also specifically induced the expression of several defence-related genes, our data suggest that XaFliC acts as a main immune response determinant in sweet orange plants.
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Affiliation(s)
- Maxuel de Oliveira Andrade
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM)CampinasBrazil
| | - Jaqueline Cristina da Silva
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM)CampinasBrazil
| | - Adriana Santos Soprano
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM)CampinasBrazil
| | - Hugo Massayoshi Shimo
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM)CampinasBrazil
| | - Adriana Franco Paes Leme
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM)CampinasBrazil
| | - Celso Eduardo Benedetti
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM)CampinasBrazil
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Ribeiro-Filho HV, Jara GE, Batista FAH, Schleder GR, Costa Tonoli CC, Soprano AS, Guimarães SL, Borges AC, Cassago A, Bajgelman MC, Marques RE, Trivella DBB, Franchini KG, Figueira ACM, Benedetti CE, Lopes-de-Oliveira PS. Structural dynamics of SARS-CoV-2 nucleocapsid protein induced by RNA binding. PLoS Comput Biol 2022; 18:e1010121. [PMID: 35551296 PMCID: PMC9129039 DOI: 10.1371/journal.pcbi.1010121] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 05/24/2022] [Accepted: 04/19/2022] [Indexed: 12/23/2022] Open
Abstract
The nucleocapsid (N) protein of the SARS-CoV-2 virus, the causal agent of COVID-19, is a multifunction phosphoprotein that plays critical roles in the virus life cycle, including transcription and packaging of the viral RNA. To play such diverse roles, the N protein has two globular RNA-binding modules, the N- (NTD) and C-terminal (CTD) domains, which are connected by an intrinsically disordered region. Despite the wealth of structural data available for the isolated NTD and CTD, how these domains are arranged in the full-length protein and how the oligomerization of N influences its RNA-binding activity remains largely unclear. Herein, using experimental data from electron microscopy and biochemical/biophysical techniques combined with molecular modeling and molecular dynamics simulations, we show that, in the absence of RNA, the N protein formed structurally dynamic dimers, with the NTD and CTD arranged in extended conformations. However, in the presence of RNA, the N protein assumed a more compact conformation where the NTD and CTD are packed together. We also provided an octameric model for the full-length N bound to RNA that is consistent with electron microscopy images of the N protein in the presence of RNA. Together, our results shed new light on the dynamics and higher-order oligomeric structure of this versatile protein. The nucleocapsid (N) protein of the SARS-CoV-2 virus plays an essential role in virus particle assembly as it specifically binds to and wraps the virus genomic RNA into a well-organized structure known as the ribonucleoprotein. Understanding how the N protein wraps around the virus RNA is critical for the development of strategies to inhibit virus assembly within host cells. One of the limitations regarding the molecular structure of the ribonucleoprotein, however, is that the N protein has several unstructured and mobile regions that preclude the resolution of its full atomic structure. Moreover, the N protein can form higher-order oligomers, both in the presence and absence of RNA. Here we employed computational methods, supported by experimental data, to simulate the N protein structural dynamics in the absence and presence of RNA. Our data suggest that the N protein forms structurally dynamic dimers in the absence of RNA, with its structured N- and C-terminal domains oriented in extended conformations. In the presence of RNA, however, the N protein assumes a more compact conformation. Our model for the oligomeric structure of the N protein bound to RNA helps to understand how N protein dimers interact to each other to form the ribonucleoprotein.
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Affiliation(s)
- Helder Veras Ribeiro-Filho
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Gabriel Ernesto Jara
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | | | - Gabriel Ravanhani Schleder
- Brazilian Nanotechnology National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Celisa Caldana Costa Tonoli
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Adriana Santos Soprano
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Samuel Leite Guimarães
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Antonio Carlos Borges
- Brazilian Nanotechnology National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Alexandre Cassago
- Brazilian Nanotechnology National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Marcio Chaim Bajgelman
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Rafael Elias Marques
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | | | - Kleber Gomes Franchini
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | | | - Celso Eduardo Benedetti
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
- * E-mail: (CEB); (PSLO)
| | - Paulo Sergio Lopes-de-Oliveira
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
- * E-mail: (CEB); (PSLO)
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Soprano AS, Smetana JHC, Benedetti CE. Regulation of tRNA biogenesis in plants and its link to plant growth and response to pathogens. Biochim Biophys Acta Gene Regul Mech 2017; 1861:344-353. [PMID: 29222070 DOI: 10.1016/j.bbagrm.2017.12.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 11/29/2017] [Accepted: 12/03/2017] [Indexed: 12/23/2022]
Abstract
The field of tRNA biology, encompassing the functional and structural complexity of tRNAs, has fascinated scientists over the years and is continuously growing. Besides their fundamental role in protein translation, new evidence indicates that tRNA-derived molecules also regulate gene expression and protein synthesis in all domains of life. This review highlights some of the recent findings linking tRNA transcription and modification with plant cell growth and response to pathogens. In fact, mutations in proteins directly involved in tRNA synthesis and modification most often lead to pleiotropic effects on plant growth and immunity. As plants need to optimize and balance their energy and nutrient resources towards growth and defense, regulatory pathways that play a central role in integrating tRNA transcription and protein translation with cell growth control and organ development, such as the auxin-TOR signaling pathway, also influence the plant immune response against pathogens. As a consequence, distinct pathogens employ an array of effector molecules including tRNA fragments to target such regulatory pathways to exploit the plant's translational capacity, gain access to nutrients and evade defenses. An example includes the RNA polymerase III repressor MAF1, a conserved component of the TOR signaling pathway that controls ribosome biogenesis and tRNA synthesis required for plant growth and which is targeted by a pathogen effector molecule to promote disease. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.
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Affiliation(s)
- Adriana Santos Soprano
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, SP, Brazil
| | - Juliana Helena Costa Smetana
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, SP, Brazil
| | - Celso Eduardo Benedetti
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, SP, Brazil.
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Soprano AS, Giuseppe POD, Shimo HM, Lima TB, Batista FAH, Righetto GL, Pereira JGDC, Granato DC, Nascimento AFZ, Gozzo FC, de Oliveira PSL, Figueira ACM, Smetana JHC, Paes Leme AF, Murakami MT, Benedetti CE. Crystal Structure and Regulation of the Citrus Pol III Repressor MAF1 by Auxin and Phosphorylation. Structure 2017; 25:1360-1370.e4. [PMID: 28781084 DOI: 10.1016/j.str.2017.07.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/16/2017] [Accepted: 07/06/2017] [Indexed: 10/25/2022]
Abstract
MAF1 is the main RNA polymerase (Pol) III repressor that controls cell growth in eukaryotes. The Citrus ortholog, CsMAF1, was shown to restrict cell growth in citrus canker disease but its role in plant development and disease is still unclear. We solved the crystal structure of the globular core of CsMAF1, which reveals additional structural elements compared with the previously available structure of hMAF1, and explored the dynamics of its flexible regions not present in the structure. CsMAF1 accumulated in the nucleolus upon leaf excision, and this translocation was inhibited by auxin and by mutation of the PKA phosphorylation site, S45, to aspartate. Additionally, mTOR phosphorylated recombinant CsMAF1 and the mTOR inhibitor AZD8055 blocked canker formation in normal but not CsMAF1-silenced plants. These results indicate that the role of TOR on cell growth induced by Xanthomonas citri depends on CsMAF1 and that auxin controls CsMAF1 interaction with Pol III in citrus.
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Affiliation(s)
- Adriana Santos Soprano
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Priscila Oliveira de Giuseppe
- Brazilian Bioethanol Science and Technology Laboratory (CTBE), Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Hugo Massayoshi Shimo
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Tatiani Brenelli Lima
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil; Institute of Chemistry, State University of Campinas, Campinas, São Paulo, Brazil
| | - Fernanda Aparecida Heleno Batista
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Germanna Lima Righetto
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - José Geraldo de Carvalho Pereira
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Daniela Campos Granato
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Andrey Fabricio Ziem Nascimento
- XALOC Beamline, Experiments Division, ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain; Structural Biology, Molecular Biology Institute of Barcelona (IBMB-CSIC), Carrer Baldiri Reixac 15, 3 A17, 08028 Barcelona, Spain
| | - Fabio Cesar Gozzo
- Institute of Chemistry, State University of Campinas, Campinas, São Paulo, Brazil
| | - Paulo Sérgio Lopes de Oliveira
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Ana Carolina Migliorini Figueira
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Juliana Helena Costa Smetana
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Adriana Franco Paes Leme
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Mario Tyago Murakami
- Brazilian Bioethanol Science and Technology Laboratory (CTBE), Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil
| | - Celso Eduardo Benedetti
- Brazilian Nacional Biosciences Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-100 Campinas, São Paulo, Brazil.
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de Souza TA, Soprano AS, de Lira NPV, Quaresma AJC, Pauletti BA, Paes Leme AF, Benedetti CE. Correction: The TAL Effector PthA4 Interacts with Nuclear Factors Involved in RNA-Dependent Processes Including a HMG Protein That Selectively Binds Poly(U) RNA. PLoS One 2015; 10:e0134818. [PMID: 26230714 PMCID: PMC4521785 DOI: 10.1371/journal.pone.0134818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Domingues MN, Sforça ML, Soprano AS, Lee J, de Souza TDACB, Cassago A, Portugal RV, de Mattos Zeri AC, Murakami MT, Sadanandom A, de Oliveira PSL, Benedetti CE. Structure and Mechanism of Dimer-Monomer Transition of a Plant Poly(A)-Binding Protein upon RNA Interaction: Insights into Its Poly(A) Tail Assembly. J Mol Biol 2015; 427:2491-2506. [PMID: 26013164 DOI: 10.1016/j.jmb.2015.05.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 05/04/2015] [Accepted: 05/19/2015] [Indexed: 12/12/2022]
Abstract
Poly(A)-binding proteins (PABPs) play crucial roles in mRNA biogenesis, stability, transport and translational control in most eukaryotic cells. Although animal PABPs are well-studied proteins, the biological role, three-dimensional structure and RNA-binding mode of plant PABPs remain largely uncharacterized. Here, we report the structural features and RNA-binding mode of a Citrus sinensis PABP (CsPABPN1). CsPABPN1 has a domain architecture of nuclear PABPs (PABPNs) with a single RNA recognition motif (RRM) flanked by an acidic N-terminus and a GRPF-rich C-terminus. The RRM domain of CsPABPN1 displays virtually the same three-dimensional structure and poly(A)-binding mode of animal PABPNs. However, while the CsPABPN1 RRM domain specifically binds poly(A), the full-length protein also binds poly(U). CsPABPN1 localizes to the nucleus of plant cells and undergoes a dimer-monomer transition upon poly(A) interaction. We show that poly(A) binding by CsPABPN1 begins with the recognition of the RNA-binding sites RNP1 and RNP2, followed by interactions with residues of the β2 strands, which stabilize the dimer, thus leading to dimer dissociation. Like human PABPN1, CsPABPN1 also seems to form filaments in the presence of poly(A). Based on these data, we propose a structural model in which contiguous CsPABPN1 RRM monomers wrap around the RNA molecule creating a superhelical structure that could not only shield the poly(A) tail but also serve as a scaffold for the assembly of additional mRNA processing factors.
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Affiliation(s)
- Mariane Noronha Domingues
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Mauricio Luis Sforça
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Adriana Santos Soprano
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Jack Lee
- School of Biological and Biomedical Sciences, Durham University, Durham, County Durham DH1, United Kingdom
| | | | - Alexandre Cassago
- Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Rodrigo Villares Portugal
- Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Ana Carolina de Mattos Zeri
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Mario Tyago Murakami
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil
| | - Ari Sadanandom
- School of Biological and Biomedical Sciences, Durham University, Durham, County Durham DH1, United Kingdom
| | | | - Celso Eduardo Benedetti
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, SP CP6192, Brazil.
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Soprano AS, Abe VY, Smetana JHC, Benedetti CE. Citrus MAF1, a repressor of RNA polymerase III, binds the Xanthomonas citri canker elicitor PthA4 and suppresses citrus canker development. Plant Physiol 2013; 163:232-42. [PMID: 23898043 PMCID: PMC3762644 DOI: 10.1104/pp.113.224642] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 07/29/2013] [Indexed: 05/23/2023]
Abstract
Transcription activator-like (TAL) effectors from Xanthomonas species pathogens act as transcription factors in plant cells; however, how TAL effectors activate host transcription is unknown. We found previously that TAL effectors of the citrus canker pathogen Xanthomonas citri, known as PthAs, bind the carboxyl-terminal domain of the sweet orange (Citrus sinensis) RNA polymerase II (Pol II) and inhibit the activity of CsCYP, a cyclophilin associated with the carboxyl-terminal domain of the citrus RNA Pol II that functions as a negative regulator of cell growth. Here, we show that PthA4 specifically interacted with the sweet orange MAF1 (CsMAF1) protein, an RNA polymerase III (Pol III) repressor that controls ribosome biogenesis and cell growth in yeast (Saccharomyces cerevisiae) and human. CsMAF1 bound the human RNA Pol III and rescued the yeast maf1 mutant by repressing tRNA(His) transcription. The expression of PthA4 in the maf1 mutant slightly restored tRNA(His) synthesis, indicating that PthA4 counteracts CsMAF1 activity. In addition, we show that sweet orange RNA interference plants with reduced CsMAF1 levels displayed a dramatic increase in tRNA transcription and a marked phenotype of cell proliferation during canker formation. Conversely, CsMAF1 overexpression was detrimental to seedling growth, inhibited tRNA synthesis, and attenuated canker development. Furthermore, we found that PthA4 is required to elicit cankers in sweet orange leaves and that depletion of CsMAF1 in X. citri-infected tissues correlates with the development of hyperplastic lesions and the presence of PthA4. Considering that CsMAF1 and CsCYP function as canker suppressors in sweet orange, our data indicate that TAL effectors from X. citri target negative regulators of RNA Pol II and Pol III to coordinately increase the transcription of host genes involved in ribosome biogenesis and cell proliferation.
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de Souza TA, Soprano AS, de Lira NPV, Quaresma AJC, Pauletti BA, Leme AFP, Benedetti CE. The TAL effector PthA4 interacts with nuclear factors involved in RNA-dependent processes including a HMG protein that selectively binds poly(U) RNA. PLoS One 2012; 7:e32305. [PMID: 22384209 PMCID: PMC3285215 DOI: 10.1371/journal.pone.0032305] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 01/26/2012] [Indexed: 11/29/2022] Open
Abstract
Plant pathogenic bacteria utilize an array of effector proteins to cause disease. Among them, transcriptional activator-like (TAL) effectors are unusual in the sense that they modulate transcription in the host. Although target genes and DNA specificity of TAL effectors have been elucidated, how TAL proteins control host transcription is poorly understood. Previously, we showed that the Xanthomonas citri TAL effectors, PthAs 2 and 3, preferentially targeted a citrus protein complex associated with transcription control and DNA repair. To extend our knowledge on the mode of action of PthAs, we have identified new protein targets of the PthA4 variant, required to elicit canker on citrus. Here we show that all the PthA4-interacting proteins are DNA and/or RNA-binding factors implicated in chromatin remodeling and repair, gene regulation and mRNA stabilization/modification. The majority of these proteins, including a structural maintenance of chromosomes protein (CsSMC), a translin-associated factor X (CsTRAX), a VirE2-interacting protein (CsVIP2), a high mobility group (CsHMG) and two poly(A)-binding proteins (CsPABP1 and 2), interacted with each other, suggesting that they assemble into a multiprotein complex. CsHMG was shown to bind DNA and to interact with the invariable leucine-rich repeat region of PthAs. Surprisingly, both CsHMG and PthA4 interacted with PABP1 and 2 and showed selective binding to poly(U) RNA, a property that is novel among HMGs and TAL effectors. Given that homologs of CsHMG, CsPABP1, CsPABP2, CsSMC and CsTRAX in other organisms assemble into protein complexes to regulate mRNA stability and translation, we suggest a novel role of TAL effectors in mRNA processing and translational control.
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Affiliation(s)
| | | | | | | | | | | | - Celso Eduardo Benedetti
- Laboratório Nacional de Biociências (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, SP, Brazil
- * E-mail:
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