The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Nuria Duran-vila - One of the best experts on this subject based on the ideXlab platform.
-
Citrus Exocortis Viroid
Viroids and Satellites, 2017Co-Authors: Nuria Duran-vilaAbstract:Abstract Citrus Exocortis Viroid , belonging to the genus PospiViroid of the family PospiViroidae , is the causal agent of the Exocortis disease. It has also been reported to affect tomato, grapevine, and certain ornamental species. It has a wide natural and experimental host range, mostly composed of symptomless Viroid–host combinations. This chapter reports its transmission, epidemiology, and economic impact, as well as the available measures for its detection and control.
-
Two nucleotide positions in the Citrus Exocortis Viroid RNA associated with symptom expression in Etrog citron but not in experimental herbaceous hosts.
Molecular plant pathology, 2010Co-Authors: Nubia Murcia, Nuria Duran-vila, Lucía Bernad, Pedro SerraAbstract:Citrus Exocortis Viroid (CEVd) is the causal agent of Exocortis disease of Citrus. CEVd has a wide host range that includes woody and herbaceous species. A new CEVd strain (CEVd(COL)), phylogenetically clustering with CEVd variants of Class A inducing severe symptoms in tomato, was identified in Colombia and shown to induce only extremely mild symptoms in Etrog citron indicator plants. Using site-directed mutagenesis, two nucleotide substitutions (314A → G and 315U → A) in the lower strand of the P domain of the predicted CEVd(COL) secondary structure resulted in a severe artificial CEVd(MCOL) variant. Conversely, two nucleotide exchanges (314G → A and 315A → U) in the same region of the severe variant CEVd(E-117) resulted in a symptomless artificial CEVd(ME-117) variant. Infectivity assays conducted with the natural and mutated variants showed that all induced severe symptoms in Gynura aurantiaca, tomato and chrysanthemum. This is the first report of the identification of pathogenic determinants of CEVd in Citrus, and shows that these pathogenicity determinants are host dependent.
-
Effect of Citrus hosts on the generation, maintenance and evolutionary fate of genetic variability of Citrus Exocortis Viroid.
Journal of General Virology, 2009Co-Authors: Lucía Bernad, Nuria Duran-vila, Santiago F. ElenaAbstract:Citrus Exocortis Viroid (CEVd) populations are composed of closely related haplotypes whose frequencies in the population result from the equilibrium between mutation, selection and genetic drift. The genetic diversity of CEVd populations infecting different Citrus hosts was studied by comparing populations recovered from infected trifoliate orange and sour orange seedling trees after 10 years of evolution, with the ancestral population maintained for the same period in the original host, Etrog citron. Furthermore, populations isolated from these trifoliate orange and sour orange trees were transmitted back to Etrog citron plants and the evolution of their mutant spectra was studied. The results indicate that (i) the amount and composition of the within-plant genetic diversity generated varies between these two hosts and is markedly different from that which is characteristic of the original Etrog citron host and (ii) the genetic diversity found after transmitting back to Etrog citron is indistinguishable from that which is characteristic of the ancestral Etrog citron population, regardless of the Citrus plant from which the evolved populations were isolated. The relationship between the CEVd populations from Etrog citron and trifoliate orange, both sensitive hosts, and those from sour orange, which is a tolerant host, is discussed.
-
Host Effect on the Molecular and Biological Properties of a Citrus Exocortis Viroid Isolate from Vicia faba.
Phytopathology, 2007Co-Authors: Mónica Gandía, Lucía Bernad, Luis Rubio, Nuria Duran-vilaAbstract:Gandia, M., Bernad, L., Rubio, L., and Duran-Vila, N. 2007. Host effect on the molecular and biological properties of a Citrus Exocortis Viroid isolate from Vicia faba. Phytopathology 97:1004-1010. Citrus Exocortis Viroid (CEVd) is the casual agent of Citrus Exocortis disease, and has been found in naturally infected Citrus and nonCitrus hosts. Field isolates of CEVd may infect susceptible hosts as a complex of genetically related sequence variants (haplotypes). In the present work, a CEVd isolate recovered from a symptomless broad bean plant was characterized as a heterogeneous population with a nucleotide diversity of 0.026, which did not contain a predominant haplotype. When nucleic acid extracts of this infected broad bean were used to inoculate tomato, the plants displayed symptoms and the CEVd population was more homogeneous, with a nucleotide diversity of 0.007. However, when nucleic acid extracts from this tomato isolate were back inoculated to new broad bean plants, this isolate did not revert to the original population, because it showed low nucleotide diversity (0.001) and induced symptoms in the broad bean plants. Symptomless broad bean plants may act as reservoirs of highly heterogeneous populations of CEVd variants, providing an excellent inoculum source in terms of its potential to infect a broad range of putative hosts. The epidemiological implications are discussed. Citrus Exocortis Viroid (CEVd) is the casual agent of Citrus Exocortis (29), a disease characterized by bark scaling symptoms in susceptible Citrus hosts. CEVd has a wide experimental host range that includes sensitive and tolerant species. CEVd also has been found naturally, occurring in nonCitrus hosts such as tomato, grapevine, eggplant, turnip, and carrot (5,8,10,15). Using tomato as an experimental host and taking into account biological properties, Visvader and Symons (34) proposed a classification of CEVd sequences into severe “class A” and mild “class B” which differ by a minimum of 26 nucleotides, mainly affecting the PL and PR regions located in the pathogenicity (P) and variable (V) domains, respectively, of the Viroid secondary structure. During a survey conducted in vegetable crops grown in eastern Spain, CEVd was identified in symptomless broad bean (Vicia faba L.) plants (6). This CEVd isolate was present in very low titers in the infected broad bean plants, but reached high titers in inoculated tomato plants, which unexpectedly remained symptomless. However, broad bean seedlings inoculated with extracts from the CEVd-infected symptomless tomato plants became stunted, had shorter internodes than the noninoculated controls, and contained Viroid titers comparable with those normally found in tomato. The consensus sequences of (i) CEVd-i, the CEVd isolate recovered from the initial source (broad bean); (ii) CEVd-t, the CEVd recovered from the inoculated tomato plants (broad bean→tomato); and (iii) CEVd-f, the CEVd from broad bean inoculated with CEVd-t (broad bean→tomato→broad bean) differed from each other and resulted in major changes in replication efficiency, host range, and pathogenicity (6). These results showed that the molecular and biological properties of the broad bean CEVd isolate were modified after passage through alternate hosts. CEVd, like genomes of other RNA pathogens, has been shown to be present in inoculated citron plants (Citrus medica L.) as populations of closely related sequences which, unlike other RNA genomes, present a low nucleotide diversity (9). Preliminary studies showed that the host may affect the genetic variability of CEVd (3). Therefore, in order to understand the evolution of CEVd-i after passage through an alternate host, it is essential to know the genetic structure of the Viroid population and the changes associated with the generation of CEVd populations having distinct replication efficiencies and biological properties. The present work describes the population structure of CEVd-i, CEVd-t, and CEVd-f and the de novo generation of populations derived from infection with a selection of single sequence variants from CEVdi and CEVd-f isolates.
-
Genetic variation and population structure of an isolate of Citrus Exocortis Viroid (CEVd) and of the progenies of two infectious sequence variants
Archives of Virology, 2005Co-Authors: Mónica Gandía, A. Palacio, L. Rubio, Nuria Duran-vilaAbstract:The population structure and diversity within a Citrus Exocortis Viroid (CEVd) isolate was estimated by single strand conformation polymorphism (SSCP) and sequence analysis. A predominant sequence variant (V1) representing 52.8% of the overall population was identified. V1 and other additional variants presented a composition of the P domain characteristic of severe strains of CEVd. The nucleotide diversity of this CEVd population was lower than expected according to a model of neutral evolution, suggesting a strong negative selection. Citron plants were inoculated with dimeric clones of nine sequence variants and two resulted infectious inducing the severe symptoms characteristic of the original isolate. De novo populations were generated from these infectious variants and like in the original CEVd isolate, both populations presented V1 as the predominant variant but they evolved to a higher nucleotide diversity.
José M. Bellés - One of the best experts on this subject based on the ideXlab platform.
-
Ethylene is Involved in Symptom Development and Ribosomal Stress of Tomato Plants upon Citrus Exocortis Viroid Infection
Plants (Basel Switzerland), 2020Co-Authors: Francisco Vázquez Prol, José M. Bellés, Ismael Rodrigo, María Pilar López-gresa, Purificación LisónAbstract:Citrus Exocortis Viroid (CEVd) is known to cause different symptoms in Citrus trees, and its mechanism of infection has been studied in tomato as an experimental host, producing ribosomal stress on these plants. Some of the symptoms caused by CEVd in tomato plants resemble those produced by the phytohormone ethylene. The present study is focused on elucidating the relationship between CEVd infection and ethylene on disease development. To this purpose, the ethylene insensitive Never ripe (Nr) tomato mutants were infected with CEVd, and several aspects such as susceptibility to infection, defensive response, ethylene biosynthesis and ribosomal stress were studied. Phenotypic characterization revealed higher susceptibility to CEVd in these mutants, which correlated with higher expression levels of both defense and ethylene biosynthesis genes, as well as the ribosomal stress marker SlNAC082. In addition, Northern blotting revealed compromised ribosome biogenesis in all CEVd infected plants, particularly in Nr mutants. Our results indicate a higher ethylene biosynthesis in Nr mutants and suggest an important role of this phytohormone in disease development and ribosomal stress caused by Viroid infection.
-
Effect of Benzothiadiazole on the Metabolome of Tomato Plants Infected by Citrus Exocortis Viroid
MDPI AG, 2019Co-Authors: María Pilar López-gresa, José M. Bellés, Ismael Rodrigo, Celia Payá, Susana Barceló, Young Hae Choi, Robert Verpoorte, Purificación LisónAbstract:Benzothiadiazole (BTH) is a functional analogue of the phytohormone salycilic acid (SA) involved in the plant immune response. NahG tomato plants are unable to accumulate SA, which makes them hypersusceptible to several pathogens. Treatments with BTH increase the resistance to bacterial, fungal, Viroid, or viral infections. In this study, metabolic alterations in BTH-treated Money Maker and NahG tomato plants infected by Citrus Exocortis Viroid (CEVd) were investigated by nuclear magnetic resonance spectroscopy. Using multivariate data analysis, we have identified defence metabolites induced after Viroid infection and BTH-treatment. Glycosylated phenolic compounds include gentisic and ferulic acid accumulated in CEVd-infected tomato plants, as well as phenylalanine, tyrosine, aspartate, glutamate, and asparagine. Besides, an increase of γ-aminobutyric acid (GABA), glutamine, adenosine, and trigonelline, contributed to a clear discrimination between the metabolome of BTH-treated tomato leaves and their corresponding controls. Among them, GABA was the only metabolite significantly accumulated in both genotypes after the chemical treatment. In view of these results, the addition of GABA was performed on tomato plants infected by CEVd, and a reversion of the NahG hypersusceptibility to CEVd was observed, indicating that GABA could regulate the resistance to CEVd induced by BTH
-
salicylic acid is involved in the basal resistance of tomato plants to Citrus Exocortis Viroid and tomato spotted wilt virus
PLOS ONE, 2016Co-Authors: Pilar M Lopezgresa, Vicente Conejero, Ismael Rodrigo, Purificación Lisón, Lynne Yenush, José M. BellésAbstract:Tomato plants expressing the NahG transgene, which prevents accumulation of endogenous salicylic acid (SA), were used to study the importance of the SA signalling pathway in basal defence against Citrus Exocortis Viroid (CEVd) or Tomato Spotted Wilt Virus (TSWV). The lack of SA accumulation in the CEVd- or TSWV-infected NahG tomato plants led to an early and dramatic disease phenotype, as compared to that observed in the corresponding parental Money Maker. Addition of acibenzolar-S-methyl, a benzothiadiazole (BTH), which activates the systemic acquired resistance pathway downstream of SA signalling, improves resistance of NahG tomato plants to CEVd and TSWV. CEVd and TSWV inoculation induced the accumulation of the hydroxycinnamic amides p-coumaroyltyramine, feruloyltyramine, caffeoylputrescine, and feruloylputrescine, and the defence related proteins PR1 and P23 in NahG plants earlier and with more intensity than in Money Maker plants, indicating that SA is not essential for the induction of these plant defence metabolites and proteins. In addition, NahG plants produced very high levels of ethylene upon CEVd or TSWV infection when compared with infected Money Maker plants, indicating that the absence of SA produced additional effects on other metabolic pathways. This is the first report to show that SA is an important component of basal resistance of tomato plants to both CEVd and TSWV, indicating that SA-dependent defence mechanisms play a key role in limiting the severity of symptoms in CEVd- and TSWV-infected NahG tomato plants.
-
Induction of gentisic acid 5-O-β-d-xylopyranoside in tomato and cucumber plants infected by different pathogens
Phytochemistry, 2006Co-Authors: Joaquín Fayos, José M. Bellés, M. Pilar López-gresa, Jaime Primo, Vicente ConejeroAbstract:Abstract Tomato plants infected with the Citrus Exocortis Viroid exhibited strongly elevated levels of a compound identified as 2,5-dihydroxybenzoic acid (gentisic acid, GA) 5- O -β- d -xylopyranoside. The compound accumulated early in leaves expressing mild symptoms from both Citrus Exocortis Viroid-infected tomato, and prunus necrotic ringspot virus-infected cucumber plants, and progressively accumulated concomitant with symptom development. The work presented here demonstrates that GA, mainly associated with systemic infections in compatible plant-pathogen interactions [Belles, J.M., Garro, R., Fayos, J., Navarro, P., Primo, J., Conejero, V., 1999. Gentisic acid as a pathogen-inducible signal, additional to salicylic acid for activation of plant defenses in tomato. Mol. Plant-Microbe Interact. 12, 227–235], is conjugated to xylose. Notably, this result contrasts with those previously found in other plant-pathogen interactions in which phenolics analogues of GA as benzoic or salicylic acids, are conjugated to glucose.
-
Correlation between Ornithine Decarboxylase and Putrescine in Tomato Plants Infected by Citrus Exocortis Viroid or Treated with Ethephon
Plant physiology, 1993Co-Authors: José M. Bellés, Miguel A. Perez-amador, Juan Carbonell, Vicente ConejeroAbstract:We have investigated the arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17) activities and the levels of conjugated polyamines to explain the decrease of free putrescine level caused by Citrus Exocortis Viroid (CEVd) and ethephon treatment in tomato (Lycopersicon esculentum Mill. cv Rutgers) plants (J.M. Belles, J. Carbonell, V. Conejero [1991] Plant Physiol 96: 1053–1059). This decrease correlates with a decrease in ODC activity in CEVd-infected or ethephon-treated plants; ADC activity was not altered. CEVd infection had no effect on polyamine conjugates, and ethephon produced a decrease in putrescine conjugates. Interference with ethylene action by silver ions prevented the decrease in ODC activity and in free and conjugated putrescine. It is suggested that changes in putrescine level after CEVd infection and ethephon treatment are regulated via ODC activity and that conjugation is not involved.
Vicente Conejero - One of the best experts on this subject based on the ideXlab platform.
-
salicylic acid is involved in the basal resistance of tomato plants to Citrus Exocortis Viroid and tomato spotted wilt virus
PLOS ONE, 2016Co-Authors: Pilar M Lopezgresa, Vicente Conejero, Ismael Rodrigo, Purificación Lisón, Lynne Yenush, José M. BellésAbstract:Tomato plants expressing the NahG transgene, which prevents accumulation of endogenous salicylic acid (SA), were used to study the importance of the SA signalling pathway in basal defence against Citrus Exocortis Viroid (CEVd) or Tomato Spotted Wilt Virus (TSWV). The lack of SA accumulation in the CEVd- or TSWV-infected NahG tomato plants led to an early and dramatic disease phenotype, as compared to that observed in the corresponding parental Money Maker. Addition of acibenzolar-S-methyl, a benzothiadiazole (BTH), which activates the systemic acquired resistance pathway downstream of SA signalling, improves resistance of NahG tomato plants to CEVd and TSWV. CEVd and TSWV inoculation induced the accumulation of the hydroxycinnamic amides p-coumaroyltyramine, feruloyltyramine, caffeoylputrescine, and feruloylputrescine, and the defence related proteins PR1 and P23 in NahG plants earlier and with more intensity than in Money Maker plants, indicating that SA is not essential for the induction of these plant defence metabolites and proteins. In addition, NahG plants produced very high levels of ethylene upon CEVd or TSWV infection when compared with infected Money Maker plants, indicating that the absence of SA produced additional effects on other metabolic pathways. This is the first report to show that SA is an important component of basal resistance of tomato plants to both CEVd and TSWV, indicating that SA-dependent defence mechanisms play a key role in limiting the severity of symptoms in CEVd- and TSWV-infected NahG tomato plants.
-
Induction of gentisic acid 5-O-β-d-xylopyranoside in tomato and cucumber plants infected by different pathogens
Phytochemistry, 2006Co-Authors: Joaquín Fayos, José M. Bellés, M. Pilar López-gresa, Jaime Primo, Vicente ConejeroAbstract:Abstract Tomato plants infected with the Citrus Exocortis Viroid exhibited strongly elevated levels of a compound identified as 2,5-dihydroxybenzoic acid (gentisic acid, GA) 5- O -β- d -xylopyranoside. The compound accumulated early in leaves expressing mild symptoms from both Citrus Exocortis Viroid-infected tomato, and prunus necrotic ringspot virus-infected cucumber plants, and progressively accumulated concomitant with symptom development. The work presented here demonstrates that GA, mainly associated with systemic infections in compatible plant-pathogen interactions [Belles, J.M., Garro, R., Fayos, J., Navarro, P., Primo, J., Conejero, V., 1999. Gentisic acid as a pathogen-inducible signal, additional to salicylic acid for activation of plant defenses in tomato. Mol. Plant-Microbe Interact. 12, 227–235], is conjugated to xylose. Notably, this result contrasts with those previously found in other plant-pathogen interactions in which phenolics analogues of GA as benzoic or salicylic acids, are conjugated to glucose.
-
Correlation between Ornithine Decarboxylase and Putrescine in Tomato Plants Infected by Citrus Exocortis Viroid or Treated with Ethephon
Plant physiology, 1993Co-Authors: José M. Bellés, Miguel A. Perez-amador, Juan Carbonell, Vicente ConejeroAbstract:We have investigated the arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17) activities and the levels of conjugated polyamines to explain the decrease of free putrescine level caused by Citrus Exocortis Viroid (CEVd) and ethephon treatment in tomato (Lycopersicon esculentum Mill. cv Rutgers) plants (J.M. Belles, J. Carbonell, V. Conejero [1991] Plant Physiol 96: 1053–1059). This decrease correlates with a decrease in ODC activity in CEVd-infected or ethephon-treated plants; ADC activity was not altered. CEVd infection had no effect on polyamine conjugates, and ethephon produced a decrease in putrescine conjugates. Interference with ethylene action by silver ions prevented the decrease in ODC activity and in free and conjugated putrescine. It is suggested that changes in putrescine level after CEVd infection and ethephon treatment are regulated via ODC activity and that conjugation is not involved.
-
Polyamines in Plants Infected by Citrus Exocortis Viroid or Treated with Silver Ions and Ethephon
Plant physiology, 1991Co-Authors: José M. Bellés, Juan Carbonell, Vicente ConejeroAbstract:The levels of polyamines in leaves of Gynura aurantiaca DC and tomato, Lycopersicon esculentum Mill. cv Rutgers, infected with Citrus Exocortis Viroid (CEVd) or treated with silver nitrate or ethephon (2-chloroethylphosphonic acid) were measured by HPLC in relation to development of symptoms. Previously it had been demonstrated that treatment of G. aurantiaca plants with silver nitrate or ethephon closely mimicked the effects of Viroid infection in the plants. In the studies reported here, a marked decrease in putrescine level was observed in plants infected by CEVd or treated with silver ions or ethephon. There was no significant change in either spermidine or spermine levels. Treatment of G. aurantiaca plants with specific inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine, Co2+) or ethylene action (norbornadiene) prevented the decrease of putrescine associated with silver nitrate treatment and had no effect on spermidine or spermine levels. The development of Viroid-like symptoms, the production of associated pathogenesis-related proteins, and the rise in protease activity induced by silver nitrate, were all suppressed by exogenous application of putrescine. The decreased level of putrescine as an ethylene-mediated step in the transduction of the Viroid and silver or ethephon signaling is discussed.
-
Suppression by Citrus Exocortis Viroid Infection of the Naturally Occurring Inhibitor of the Conversion of 1‐aminocyclopropane‐1‐carboxylic Acid to Ethylene by Tomato Microsomes
Journal of Phytopathology, 1991Co-Authors: José M. Bellés, Vicente ConejeroAbstract:Citrus Exocortis Viroid (CEVd) infection of tomato cell cultures suppresses the constitutive inhibitor which blocks the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by tomato microsomes. The inhibitor is associated to microsomal membranes and is also found in the water soluble fraction co-isolated from the cells. The inhibitory effect is concentration dependent, heat stable and could be removed from solution by dialysis. Its possible relationship with regulation of the Viroid-induced ethylene production is discussed.
Purificación Lisón - One of the best experts on this subject based on the ideXlab platform.
-
Ethylene is Involved in Symptom Development and Ribosomal Stress of Tomato Plants upon Citrus Exocortis Viroid Infection
Plants (Basel Switzerland), 2020Co-Authors: Francisco Vázquez Prol, José M. Bellés, Ismael Rodrigo, María Pilar López-gresa, Purificación LisónAbstract:Citrus Exocortis Viroid (CEVd) is known to cause different symptoms in Citrus trees, and its mechanism of infection has been studied in tomato as an experimental host, producing ribosomal stress on these plants. Some of the symptoms caused by CEVd in tomato plants resemble those produced by the phytohormone ethylene. The present study is focused on elucidating the relationship between CEVd infection and ethylene on disease development. To this purpose, the ethylene insensitive Never ripe (Nr) tomato mutants were infected with CEVd, and several aspects such as susceptibility to infection, defensive response, ethylene biosynthesis and ribosomal stress were studied. Phenotypic characterization revealed higher susceptibility to CEVd in these mutants, which correlated with higher expression levels of both defense and ethylene biosynthesis genes, as well as the ribosomal stress marker SlNAC082. In addition, Northern blotting revealed compromised ribosome biogenesis in all CEVd infected plants, particularly in Nr mutants. Our results indicate a higher ethylene biosynthesis in Nr mutants and suggest an important role of this phytohormone in disease development and ribosomal stress caused by Viroid infection.
-
Citrus Exocortis Viroid causes ribosomal stress in tomato plants.
Nucleic acids research, 2019Co-Authors: Patrick Cottilli, Borja Belda-palazón, Charith Raj Adkar-purushothama, Jean-pierre Perreault, Enrico Schleiff, Ismael Rodrigo, Alejandro Ferrando, Purificación LisónAbstract:Viroids are naked RNAs that do not code for any known protein and yet are able to infect plants causing severe diseases. Because of their RNA nature, many studies have focused on the involvement of Viroids in RNA-mediated gene silencing as being their pathogenesis mechanism. Here, the alterations caused by the Citrus Exocortis Viroid (CEVd) on the tomato translation machinery were studied as a new aspect of Viroid pathogenesis. The presence of Viroids in the ribosomal fractions of infected tomato plants was detected. More precisely, CEVd and its derived Viroid small RNAs were found to co-sediment with tomato ribosomes in vivo, and to provoke changes in the global polysome profiles, particularly in the 40S ribosomal subunit accumulation. Additionally, the Viroid caused alterations in ribosome biogenesis in the infected tomato plants, affecting the 18S rRNA maturation process. A higher expression level of the ribosomal stress mediator NAC082 was also detected in the CEVd-infected tomato leaves. Both the alterations in the rRNA processing and the induction of NAC082 correlate with the degree of Viroid symptomatology. Taken together, these results suggest that CEVd is responsible for defective ribosome biogenesis in tomato, thereby interfering with the translation machinery and, therefore, causing ribosomal stress.
-
Effect of Benzothiadiazole on the Metabolome of Tomato Plants Infected by Citrus Exocortis Viroid
MDPI AG, 2019Co-Authors: María Pilar López-gresa, José M. Bellés, Ismael Rodrigo, Celia Payá, Susana Barceló, Young Hae Choi, Robert Verpoorte, Purificación LisónAbstract:Benzothiadiazole (BTH) is a functional analogue of the phytohormone salycilic acid (SA) involved in the plant immune response. NahG tomato plants are unable to accumulate SA, which makes them hypersusceptible to several pathogens. Treatments with BTH increase the resistance to bacterial, fungal, Viroid, or viral infections. In this study, metabolic alterations in BTH-treated Money Maker and NahG tomato plants infected by Citrus Exocortis Viroid (CEVd) were investigated by nuclear magnetic resonance spectroscopy. Using multivariate data analysis, we have identified defence metabolites induced after Viroid infection and BTH-treatment. Glycosylated phenolic compounds include gentisic and ferulic acid accumulated in CEVd-infected tomato plants, as well as phenylalanine, tyrosine, aspartate, glutamate, and asparagine. Besides, an increase of γ-aminobutyric acid (GABA), glutamine, adenosine, and trigonelline, contributed to a clear discrimination between the metabolome of BTH-treated tomato leaves and their corresponding controls. Among them, GABA was the only metabolite significantly accumulated in both genotypes after the chemical treatment. In view of these results, the addition of GABA was performed on tomato plants infected by CEVd, and a reversion of the NahG hypersusceptibility to CEVd was observed, indicating that GABA could regulate the resistance to CEVd induced by BTH
-
salicylic acid is involved in the basal resistance of tomato plants to Citrus Exocortis Viroid and tomato spotted wilt virus
PLOS ONE, 2016Co-Authors: Pilar M Lopezgresa, Vicente Conejero, Ismael Rodrigo, Purificación Lisón, Lynne Yenush, José M. BellésAbstract:Tomato plants expressing the NahG transgene, which prevents accumulation of endogenous salicylic acid (SA), were used to study the importance of the SA signalling pathway in basal defence against Citrus Exocortis Viroid (CEVd) or Tomato Spotted Wilt Virus (TSWV). The lack of SA accumulation in the CEVd- or TSWV-infected NahG tomato plants led to an early and dramatic disease phenotype, as compared to that observed in the corresponding parental Money Maker. Addition of acibenzolar-S-methyl, a benzothiadiazole (BTH), which activates the systemic acquired resistance pathway downstream of SA signalling, improves resistance of NahG tomato plants to CEVd and TSWV. CEVd and TSWV inoculation induced the accumulation of the hydroxycinnamic amides p-coumaroyltyramine, feruloyltyramine, caffeoylputrescine, and feruloylputrescine, and the defence related proteins PR1 and P23 in NahG plants earlier and with more intensity than in Money Maker plants, indicating that SA is not essential for the induction of these plant defence metabolites and proteins. In addition, NahG plants produced very high levels of ethylene upon CEVd or TSWV infection when compared with infected Money Maker plants, indicating that the absence of SA produced additional effects on other metabolic pathways. This is the first report to show that SA is an important component of basal resistance of tomato plants to both CEVd and TSWV, indicating that SA-dependent defence mechanisms play a key role in limiting the severity of symptoms in CEVd- and TSWV-infected NahG tomato plants.
José-antonio Daròs - One of the best experts on this subject based on the ideXlab platform.
-
monomeric linear rna of Citrus Exocortis Viroid resulting from processing in vivo has 5 phosphomonoester and 3 hydroxyl termini implications for the rnase and rna ligase involved in replication
Journal of Virology, 2008Co-Authors: María-eugenia Gas, Carmen Hernández, Ricardo Flores, Diego Molinaserrano, José-antonio DaròsAbstract:Members of the family PospiViroidae, like Citrus Exocortis Viroid (CEVd), replicate through an RNA-based asymmetric rolling-circle mechanism in which oligomeric plus-strand [(+)] RNA intermediates are cleaved to monomeric linear (ml) RNA and then circularized. Here we show, by rapid amplification of 5' and 3' cDNA ends and in vitro ligation assays, that ml CEVd (+) RNA resulting from cleavage of a dimeric transcript transgenically expressed in Arabidopsis thaliana contains 5'-phosphomonoester and 3'-hydroxyl termini. The nature of these termini and the double-stranded structure previously proposed as the substrate for cleavage in vivo suggest that a type III RNase catalyzes cleavage and an RNA ligase distinct from tRNA ligase promotes circularization.
-
Monomeric Linear RNA of Citrus Exocortis Viroid Resulting from Processing In Vivo Has 5′-Phosphomonoester and 3′-Hydroxyl Termini: Implications for the RNase and RNA Ligase Involved in Replication
Journal of virology, 2008Co-Authors: María-eugenia Gas, Carmen Hernández, Ricardo Flores, Diego Molina-serrano, José-antonio DaròsAbstract:Members of the family PospiViroidae, like Citrus Exocortis Viroid (CEVd), replicate through an RNA-based asymmetric rolling-circle mechanism in which oligomeric plus-strand [(+)] RNA intermediates are cleaved to monomeric linear (ml) RNA and then circularized. Here we show, by rapid amplification of 5' and 3' cDNA ends and in vitro ligation assays, that ml CEVd (+) RNA resulting from cleavage of a dimeric transcript transgenically expressed in Arabidopsis thaliana contains 5'-phosphomonoester and 3'-hydroxyl termini. The nature of these termini and the double-stranded structure previously proposed as the substrate for cleavage in vivo suggest that a type III RNase catalyzes cleavage and an RNA ligase distinct from tRNA ligase promotes circularization.
-
characterization of small rnas derived from Citrus Exocortis Viroid cevd in infected tomato plants
Virology, 2007Co-Authors: Raquel Martin, José-antonio Daròs, Catalina Arenas, Alejandra A Covarrubias, Jose Luis Reyes, Namhai ChuaAbstract:In plants, RNA silencing provides an adaptive immune system that inactivates pathogenic nucleic acids, guided by 21–24-mer RNAs of pathogen origin. The characterization of pathogen-related small RNAs (sRNAs) is relevant to uncovering the strategies used by pathogens to evade host defense responses. Several groups have reported the detection of Viroid-derived sRNAs during infections, although the origin of these sRNAs and their chemical characteristics were poorly understood. Here, we describe the in vivo cleavage of Citrus Exocortis Viroid (CEVd) RNA into sRNAs of 21–22 nt, that are phosphorylated at their 5′-end and methylated at 3′. Our studies suggested that the CEVd genomic RNA might be the predominant in vivo substrate for cleavage by Dicer-like enzyme(s), which preferentially targeted residues mainly located within the right-end domain of the Viroid. Further analysis on the accumulation levels of specific miRNAs controlling major regulators of leaf development and the miRNA pathway and the levels of their target mRNAs provided evidence that the endogenous tomato miRNA pathway was not affected by CEVd infection.
-
Identification in eggplant of a variant of Citrus Exocortis Viroid (CEVd) with a 96 nucleotide duplication in the right terminal region of the rod-like secondary structure.
Virus research, 2003Co-Authors: Z. Fadda, José-antonio Daròs, Ricardo Flores, Nuria Duran-vilaAbstract:Analysis of eggplants, kept for years under greenhouse conditions after having been mechanically inoculated with nucleic acid preparations from field-grown eggplants containing two Viroids, Eggplant latent Viroid (ELVd) and Citrus Exocortis Viroid (CEVd), revealed the presence of an additional larger Viroid RNA. Molecular characterization of this RNA showed that it is a stable 467-nt variant of CEVd with a 96-nt duplication of the right terminal region (CEVd-D96) that preserves the rod-like secondary structure. The coexistence in eggplant of CEVd (371 nt) and CEVd-D96, and the fact that they have an almost identical sequence, strongly suggests the emergence of the latter from the former through an internal recombination mediated by a jumping RNA polymerase with low processivity. CEVd-D96 from eggplant is similar to the CEVd-D92 variant characterized previously in a hybrid tomato, suggesting that certain hosts may play a critical role in selecting and replicating this class of enlarged variants.