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Moreno P, López C, Ruiz-Ruiz S, Peña L, Guerri J. From the smallest to the largest subcellular plant pathogen: Citrus tristeza virus and its unique p23 protein. Virus Res 2022; 314:198755. [PMID: 35341876 DOI: 10.1016/j.virusres.2022.198755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/07/2022] [Accepted: 03/23/2022] [Indexed: 10/18/2022]
Abstract
Knowledge on diseases caused by Citrus tristeza virus (CTV) has greatly increased in last decades after their etiology was demonstrated in the past seventies. Professor Ricardo Flores substantially contributed to these advances in topics like: i) improvement of virus purification to obtain biologically active virions, ii) sequencing mild CTV isolates for genetic comparisons with sequences of moderate or severe isolates and genetic engineering, iii) analysis of genetic variation of both CTV genomic RNA ends and features of the highly variable 5' end that allow accommodating this variation within a conserved secondary structure, iv) studies on the structure, subcellular localization and biological functions of the CTV-unique p23 protein, and v) potential use of p23 and other 3'-proximal regions of the CTV genome to develop transgenic citrus resistant to the virus. Here we review his main achievements on these topics and how they contributed to deeper understanding of CTV biology and to new potential measures for disease control.
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Affiliation(s)
- Pedro Moreno
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, 46113-Valencia, Spain. (Retired).
| | - Carmelo López
- Instituto de Conservación y Mejora de la Agrodiversidad Valenciana (COMAV), Universitat Politècnica de València, 46022-Valencia, Spain
| | - Susana Ruiz-Ruiz
- Unidad Mixta de Investigación en Genómica y Salud, Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunitat Valenciana (FISABIO), 46022-Valencia, Spain
| | - Leandro Peña
- Instituto de Biología Molecular y Celular de Plantas (IBMCP). Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), 46022-Valencia, Spain
| | - José Guerri
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, 46113-Valencia, Spain. (Retired)
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In Memoriam of Ricardo Flores: The Career, Achievements, and Legacy of an inspirational plant virologist. Virus Res 2022. [DOI: 10.1016/j.virusres.2022.198718] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Davino S, Ruiz-Ruiz S, Serra P, Forment J, Flores R. Revisiting the cysteine-rich proteins encoded in the 3'-proximal open reading frame of the positive-sense single-stranded RNA of some monopartite filamentous plant viruses: functional dissection of p15 from grapevine virus B. Arch Virol 2020; 165:2229-2239. [PMID: 32676682 DOI: 10.1007/s00705-020-04729-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 06/09/2020] [Indexed: 10/23/2022]
Abstract
A reexamination of proteins with conserved cysteines and basic amino acids encoded by the 3'-proximal gene of the positive-sense single-stranded RNA of some monopartite filamentous plant viruses has been carried out. The cysteines are involved in a putative Zn-finger domain, which, together with the basic amino acids, form part of the nuclear or nucleolar localization signals. An in-depth study of one of these proteins, p15 from grapevine B virus (GVB), has shown: (i) a three-dimensional structure with four α-helices predicted by two independent in silico approaches, (ii) the nucleolus as the main accumulation site by applying confocal laser microscopy to a fusion between p15 and the green fluorescent protein, (iii) the involvement of the basic amino acids and the putative Zn-finger domain, mapping at the N-terminal region of p15, in the nucleolar localization signal, as revealed by the effect of six alanine substitution mutations, (iv) the p15 suppressor function of sense-mediated RNA silencing as revealed by agroinfiltration in a transgenic line of Nicotiana benthamiana, and (v) the enhancer activity of p15 on viral pathogenicity in N. benthamiana when expressed from a potato virus X vector. In addition, we elaborate on an evolutionary scenario for these filamentous viruses, invoking takeover by a common ancestor(s) of viral or host genes coding for those cysteine-rich proteins, followed by divergence, which would also explain why they are encoded in the 3'-proximal gene of the genomic single-stranded viral RNA.
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Affiliation(s)
- Salvatore Davino
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
- Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze Building 5, 90128, Palermo, Italy
| | - Susana Ruiz-Ruiz
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
| | - Pedro Serra
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
| | - Javier Forment
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
| | - Ricardo Flores
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain.
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Sanfaçon H. Modulation of disease severity by plant positive-strand RNA viruses: The complex interplay of multifunctional viral proteins, subviral RNAs and virus-associated RNAs with plant signaling pathways and defense responses. Adv Virus Res 2020; 107:87-131. [PMID: 32711736 DOI: 10.1016/bs.aivir.2020.04.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Plant viruses induce a range of symptoms of varying intensity, ranging from severe systemic necrosis to mild or asymptomatic infection. Several evolutionary constraints drive virus virulence, including the dependence of viruses on host factors to complete their infection cycle, the requirement to counteract or evade plant antiviral defense responses and the mode of virus transmission. Viruses have developed an array of strategies to modulate disease severity. Accumulating evidence has highlighted not only the multifunctional role that viral proteins play in disrupting or highjacking plant factors, hormone signaling pathways and intracellular organelles, but also the interaction networks between viral proteins, subviral RNAs and/or other viral-associated RNAs that regulate disease severity. This review focusses on positive-strand RNA viruses, which constitute the majority of characterized plant viruses. Using well-characterized viruses with different genome types as examples, recent advances are discussed as well as knowledge gaps and opportunities for further research.
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Affiliation(s)
- Hélène Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada.
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Nehela Y, Killiny N. The unknown soldier in citrus plants: polyamines-based defensive mechanisms against biotic and abiotic stresses and their relationship with other stress-associated metabolites. PLANT SIGNALING & BEHAVIOR 2020; 15:1761080. [PMID: 32408848 PMCID: PMC8570725 DOI: 10.1080/15592324.2020.1761080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/20/2020] [Accepted: 04/21/2020] [Indexed: 05/07/2023]
Abstract
Citrus plants are challenged by a broad diversity of abiotic and biotic stresses, which definitely alter their growth, development, and productivity. In order to survive the various stressful conditions, citrus plants relay on multi-layered adaptive strategies, among which is the accumulation of stress-associated metabolites that play vital and complex roles in citrus defensive responses. These metabolites included amino acids, organic acids, fatty acids, phytohormones, polyamines (PAs), and other secondary metabolites. However, the contribution of PAs pathways in citrus defense responses is poorly understood. In this review article, we will discuss the recent metabolic, genetic, and molecular evidence illustrating the potential roles of PAs in citrus defensive responses against biotic and abiotic stressors. We believe that PAs-based defensive role, against biotic and abiotic stress in citrus, is involving the interaction with other stress-associated metabolites, particularly phytohormones. The knowledge gained so far about PAs-based defensive responses in citrus underpins our need for further genetic manipulation of PAs biosynthetic genes to produce transgenic citrus plants with modulated PAs content that may enhance the tolerance of citrus plants against stressful conditions. In addition, it provides valuable information for the potential use of PAs or their synthetic analogs and their emergence as a promising approach to practical applications in citriculture to enhance stress tolerance in citrus plants.
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Affiliation(s)
- Yasser Nehela
- Citrus Research and Education Center and Department of Plant Pathology, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Nabil Killiny
- Citrus Research and Education Center and Department of Plant Pathology, IFAS, University of Florida, Lake Alfred, FL, USA
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Ruiz-Ruiz S, Navarro B, Peña L, Navarro L, Moreno P, Di Serio F, Flores R. Citrus tristeza virus: Host RNA Silencing and Virus Counteraction. Methods Mol Biol 2019; 2015:195-207. [PMID: 31222705 DOI: 10.1007/978-1-4939-9558-5_14] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To dissect the host RNA silencing response incited by citrus tristeza virus (CTV, genus Closterovirus), a (+) ssRNA of ~19300 nt, and the counter reaction deployed by the virus via its three RNA silencing suppressors (RSS), the small RNAs (sRNAs) of three virus-host combinations were deep sequenced. The subsequent analysis indicated that CTV sRNAs (1) constitute more than half of the total sRNAs in the susceptible Mexican lime and sweet orange, while only 3.5% in the restrictive sour orange; (2) are mostly of 21-22 nt, with those of (+) sense predominating slightly; and (3) derive from all the CTV genome, as evidenced by its entire recomposition from viral sRNA contigs but adopt an asymmetric pattern with a hotspot mapping at the 3'-terminal ~2500 nt. The citrus homologues of Arabidopsis Dicer-like (DCL) 4 and 2 most likely generate the 21 and 22 nt CTV sRNAs, respectively, by dicing the gRNA and the 3' co-terminal sgRNAs and, particularly, their double-stranded forms accumulating in infected cells. The plant sRNA profile, very similar and dominated by the 24 nt sRNAs in the three mock-inoculated controls, displayed a major reduction of the 24 nt sRNAs in Mexican lime and sweet orange, but not in sour orange. CTV infection also influences the levels of certain microRNAs.The high accumulation of CTV sRNAs in two of the citrus hosts examined suggests that it is not their synthesis, but their function, the target of the RSS encoded by CTV: p25 (intercellular), p23 (intracellular) and p20 (both). The two latter might block the loading of CTV sRNAs into the RNA silencing complex or interfere with it through alternative mechanisms. Of the three CTV RSS, p23 is the one that has been more thoroughly studied. It is a multifunctional RNA-binding protein with a putative Zn finger domain and basic motifs that (1) has no homologues in other closteroviruses, (2) accumulates in the nucleolus and plasmodesmata, (3) regulates the asymmetric balance of CTV (+) and (-) RNA strands, and (4) induces CTV syndromes and stimulates systemic infection in certain citrus species when expressed as a transgene ectopically or in phloem-associated cells.
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Affiliation(s)
- Susana Ruiz-Ruiz
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | - Beatriz Navarro
- Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Bari, Italy
| | - Leandro Peña
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain.,Instituto Valenciano de Investigaciones Agrarias, Moncada, Spain
| | - Luis Navarro
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Pedro Moreno
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Francesco Di Serio
- Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Bari, Italy
| | - Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain.
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Ruiz-Ruiz S, Spanò R, Navarro L, Moreno P, Peña L, Flores R. Citrus tristeza virus co-opts glyceraldehyde 3-phosphate dehydrogenase for its infectious cycle by interacting with the viral-encoded protein p23. PLANT MOLECULAR BIOLOGY 2018; 98:363-373. [PMID: 30392159 PMCID: PMC7088584 DOI: 10.1007/s11103-018-0783-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 10/01/2018] [Indexed: 05/03/2023]
Abstract
KEY MESSAGE Citrus tristeza virus encodes a unique protein, p23, with multiple functional roles that include co-option of the cytoplasmic glyceraldehyde 3-phosphate dehydrogenase to facilitate the viral infectious cycle. The genome of citrus tristeza virus (CTV), genus Closterovirus family Closteroviridae, is a single-stranded (+) RNA potentially encoding at least 17 proteins. One (p23), an RNA-binding protein of 209 amino acids with a putative Zn-finger and some basic motifs, displays singular features: (i) it has no homologues in other closteroviruses, (ii) it accumulates mainly in the nucleolus and Cajal bodies, and in plasmodesmata, and (iii) it mediates asymmetric accumulation of CTV RNA strands, intracellular suppression of RNA silencing, induction of some CTV syndromes and enhancement of systemic infection when expressed as a transgene ectopically or in phloem-associated cells in several Citrus spp. Here, a yeast two-hybrid screening of an expression library of Nicotiana benthamiana (a symptomatic experimental host for CTV), identified a transducin/WD40 domain protein and the cytosolic glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as potential host interactors with p23. Bimolecular fluorescence complementation corroborated the p23-GAPDH interaction in planta and showed that p23 interacts with itself in the nucleolus, Cajal bodies and plasmodesmata, and with GAPDH in the cytoplasm (forming aggregates) and in plasmodesmata. The latter interaction was preserved in a p23 deletion mutant affecting the C-terminal domain, but not in two others affecting the Zn-finger and one internal basic motif. Virus-induced gene silencing of GAPDH mRNA resulted in a decrease of CTV titer as revealed by real-time RT-quantitative PCR and RNA gel-blot hybridization. Thus, like other viruses, CTV seems to co-opt GAPDH, via interaction with p23, to facilitate its infectious cycle.
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Affiliation(s)
- Susana Ruiz-Ruiz
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain
| | - Roberta Spanò
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain
- Dipartimento di Scienze del Suolo della Pianta e degli Alimenti, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Luis Navarro
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain
| | - Pedro Moreno
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain
| | - Leandro Peña
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain
| | - Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain.
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Gómez‐Muñoz N, Velázquez K, Vives MC, Ruiz‐Ruiz S, Pina JA, Flores R, Moreno P, Guerri J. The resistance of sour orange to Citrus tristeza virus is mediated by both the salicylic acid and RNA silencing defence pathways. MOLECULAR PLANT PATHOLOGY 2017; 18:1253-1266. [PMID: 27588892 PMCID: PMC6638288 DOI: 10.1111/mpp.12488] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 08/26/2016] [Accepted: 08/30/2016] [Indexed: 05/08/2023]
Abstract
Citrus tristeza virus (CTV) induces in the field the decline and death of citrus varieties grafted on sour orange (SO) rootstock, which has forced the use of alternative decline-tolerant rootstocks in affected countries, despite the highly desirable agronomic features of the SO rootstock. Declining citrus plants display phloem necrosis below the bud union. In addition, SO is minimally susceptible to CTV compared with other citrus varieties, suggesting partial resistance of SO to CTV. Here, by silencing different citrus genes with a Citrus leaf blotch virus-based vector, we have examined the implication of the RNA silencing and salicylic acid (SA) defence pathways in the resistance of SO to CTV. Silencing of the genes RDR1, NPR1 and DCL2/DCL4, associated with these defence pathways, enhanced virus spread and accumulation in SO plants in comparison with non-silenced controls, whereas silencing of the genes NPR3/NPR4, associated with the hypersensitive response, produced a slight decrease in CTV accumulation and reduced stunting of SO grafted on CTV-infected rough lemon plants. We also found that the CTV RNA silencing suppressors p20 and p23 also suppress the SA signalling defence, with the suppressor activity being higher in the most virulent isolates.
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Affiliation(s)
- Neus Gómez‐Muñoz
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - Karelia Velázquez
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - María Carmen Vives
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - Susana Ruiz‐Ruiz
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - José Antonio Pina
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas (UPV‐CSIC), Universidad Politécnica de Valencia, Avenida de los NaranjosValencia46022Spain
| | - Pedro Moreno
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - José Guerri
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
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Dawson WO, Bar-Joseph M, Garnsey SM, Moreno P. Citrus tristeza virus: making an ally from an enemy. ANNUAL REVIEW OF PHYTOPATHOLOGY 2015; 53:137-55. [PMID: 25973695 DOI: 10.1146/annurev-phyto-080614-120012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Virus diseases of perennial trees and vines have characteristics not amenable to study using small model annual plants. Unique disease symptoms such as graft incompatibilities and stem pitting cause considerable crop losses. Also, viruses in these long-living plants tend to accumulate complex populations of viruses and strains. Considerable progress has been made in understanding the biology and genetics of Citrus tristeza virus (CTV) and in developing it into a tool for crop protection and improvement. The diseases in tree and vine crops have commonalities for which CTV can be used to develop a baseline. The purpose of this review is to provide a necessary background of systems and reagents developed for CTV that can be used for continued progress in this area and to point out the value of the CTV-citrus system in answering important questions on plant-virus interactions and developing new methods for controlling plant diseases.
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Affiliation(s)
- William O Dawson
- Department of Plant Pathology, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850; ,
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