Abstract: The molecular biology, epidemiology, and evolutionary dynamics of Pepino mosaic virus (PepMV) are much better understood than those of Tomato torrado virus (ToTV). The earliest descriptions of PepMV suggest a recent jump from nontomato species (e.g., pepino; Solanum muricatum) to tomato (Solanum lycopersicum). Its stability in contaminated plant tissues, its transmission through seeds, and the global trade of tomato seeds and fruits may have facilitated the global spread of PepMV. Stability and seed transmission also probably account for the devastating epidemics caused by already-established PepMV strains, although additional contributing factors may include the efficient transmission of PepMV by contact and the often-inconspicuous symptoms in vegetative tomato tissues. The genetic variability of PepMV is likely to have promoted the first phase of emergence (i.e., the species jump) and it continues to play an important role as the virus becomes more pervasive, progressing from regional outbreaks to pandemics. In contrast, the long-term progression of ToTV outbreaks is not yet clear and this may reflect factors such as the limited accumulation of the virus in infected plants, which has been shown to be approximately two orders of magnitude less than PepMV. The efficient dispersion of ToTV may therefore depend on dense populations of its principal vectors, Bemisia tabaci and Trialeurodes vaporariorum, as has been proposed for the necrogenic satellite RNA of Cucumber mosaic virus.
Notes: ISI Document Delivery No.: BBI07 Times Cited: 0 Cited Reference Count: 105 Gomez, Pedro Sempere, Raquel N. Aranda, Miguel A. Review; Book Chapter 525 b street, suite 1900, san diego, ca 92101-4495 usa
Abstract: Flavonoids in Citrus sp. are a widely distributed group of polyphenolic compounds characterized by a common benzo-gamma-pyrone structure. Flavonoids are present in a large variety of edible plants, especially in Citrus species. All flavonoids described in Citrus sp. to date can be classified into four clearly differentiated groups: flavones, flavonols, flavanones and their corresponding glycosides with these two possible types of of glycoside substitution: beta-neohesperidos ides (2-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranose) or beta-rutinoside (6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranose) (1). Depending on the particular citrus species, the biosynthetic pathways result in the synthesis of: naringin, the 7-beta-neohesperidoside of naringenin (4',5,7-trihydroxyflavone), which is the major flavonoid in Citrus paradisi; neohesperidin, the 7-beta-neohesperidoside of hesperetin (3',5,7-trihydroxy-4'methoxy flavanone), which is the principal flavonoid in Citrus aurantium; or hesperidin, the 7-beta-rutinoside of hesperetin, which is the principal flavonoid in Citrus sinensis and Citrus limon (Figure 1). The flavanone glycosides are accumulated in the greatest quantity, although the concentration of these compounds depends on the age of the plant. The highest concentration occur in young tissues showing pronounced cell divisions, in which they may represent 40-45% of the dry weight (2-8). However, less is known about other structural groups of Citrus flavonoids, the flavones and flavonols, although they have been studied in greater depth in other plant families (9).
Notes: Times Cited: 1 228th National Meeting of the American-Chemical-Society Aug 22-26, 2004 Philadelphia, PA Amer Chem Soc; Amer Chem Soc, Fuel Chem Div; Amer Chem Soc, Petr Chem Div
Abstract: Bacteria undergo adaptive diversification over a matter of days in test tubes, but the relevance to natural populations remains unclear. Here, we report real-time adaptive diversification of the bacterium Pseudomonas fluorescens in its natural environment, soil. Crucially, adaptive diversification was much greater in the absence of the established natural microbial community, suggesting that resident diversity is likely to inhibit, rather than promote, adaptive radiations in natural environments. Rapid diversification is therefore likely to play an important role in the population and community dynamics of microbes in environments where resident communities are perturbed, such as by agriculture, pollution and antibiotics.
Abstract: Viral diseases that could cause important economic losses often affect cucurbits, but only limited information on the incidence and spatial distribution of specific viruses is currently available. During the 2005 and 2006 growing seasons, systematic surveys were carried out in open field melon (Cucumis melo), squash and pumpkin (Cucurbita pepo), watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) crops of the Spanish Community of Valencia (eastern Spain), where several counties have a long standing tradition of cucurbit cultivation and production. Surveyed fields were chosen with no previous information as to their sanitation status, and samples were taken from plants that showed virus-like symptoms. Samples were analysed using molecular hybridisation to detect Beet pseudo-yellows virus (BPYV), Cucurbit aphid-borne yellows virus (CABYV), Cucumber mosaic virus (CMV), Cucumber vein yellowing virus (CVYV), Cucurbit yellow stunting disorder virus (CYSDV), Melon necrotic spot virus (MNSV), Papaya ring spot virus (PRSV), Watermelon mosaic virus (WMV) and Zucchini yellow mosaic virus (ZYMV). We collected 1767 samples from 122 independent field plots; out of these, approximately 94% of the samples were infected by at least one of these viruses. Percentages for the more frequently detected viruses were 35.8%, 27.0%, 16.5% and 7.2% for CABYV, WMV, PRSV and ZYMV, respectively, and significant deviations were found on the frequency distributions based on either the area or the host sampled. The number of multiple infections was high (average 36%), particularly for squash (more than 57%), with the most frequent combination being WMVâ+âPRSV (12%) followed by WMVâ+âCABYV (10%). Sequencing of WMV complementary DNA suggested that âemergingâ isolates have replaced the âclassicâ ones, as described in southern regions of France, leading us to believe that cucurbit cultivation could be severely affected by these new, emerging isolates.
Abstract: Pepino mosaic virus (PepMV) is an emerging pathogen that causes severe economic losses in tomato crops in the Northern hemisphere. After its first identification, the new viral strain PepMV-CH2 has been isolated in several countries worldwide. In order to further understand the evolutionary dynamics of PepMV before and after PepMV-CH2 emergence, we analyzed a collection of PepMV isolates from southeastern Spain, estimating the rate of PepMV molecular evolution and the coalescence process for the effective number of PepMV infections using a Bayesian phylogenetic approach. Our results show that the rate of PepMV molecular evolution was 5.570 Ã 10 â3 substitutions/site/year, a value which is approximately an order of magnitude higher than the rates recently reported for other plant RNA viruses. Moreover, PepMV-CH2 was estimated to have originated in 2000, coincident with the onset of PepMV-CH2 infections in southeastern Spain, its population following now an expansion process. This further illustrates that genetic and ecological interactions among different viral strains can modulate the evolutionary dynamics of PepMV and determine its epidemiological profile.
Abstract: BACKGROUND:Plant viruses are useful expression vectors because they can mount systemic infections allowing large amounts of recombinant protein to be produced rapidly in differentiated plant tissues. Pepino mosaic virus (PepMV) (genus Potexvirus, family Flexiviridae), a widespread plant virus, is a promising candidate expression vector for plants because of its high level of accumulation in its hosts and the absence of severe infection symptoms. We report here the construction of a stable and efficient expression vector for plants based on PepMV.RESULTS:Agroinfectious clones were produced from two different PepMV genotypes (European and Chilean), and these were able to initiate typical PepMV infections. We explored several strategies for vector development including coat protein (CP) replacement, duplication of the CP subgenomic promoter (SGP) and the creation of a fusion protein using the foot-and-mouth disease virus (FMDV) 2A catalytic peptide. We found that CP replacement vectors were unable to move systemically and that vectors with duplicated SGPs (even heterologous SGPs) suffered from significant transgene instability. The fusion protein incorporating the FMDV 2A catalytic peptide gave by far the best results, maintaining stability through serial passages and allowing the accumulation of GFP to 0.2-0.4 g per kg of leaf tissue. The possible use of PepMV as a virus-induced gene silencing vector to study gene function was also demonstrated. Protocols for the use of this vector are described.CONCLUSIONS:A stable PepMV vector was generated by expressing the transgene as a CP fusion using the sequence encoding the foot-and-mouth disease virus (FMDV) 2A catalytic peptide to separate them. We have generated a novel tool for the expression of recombinant proteins in plants and for the functional analysis of virus and plant genes. Our experiments have also highlighted virus requirements for replication in single cells as well as intercellular and long-distance movement.
Abstract: Bacteria and their viruses (phages) undergo rapid coevolution in test tubes, but the relevance to natural environments is unclear. By using a âmark-recaptureâ approach, we showed rapid coevolution of bacteria and phages in a soil community. Unlike coevolution in vitro, which is characterized by increases in infectivity and resistance through time (arms race dynamics), coevolution in soil resulted in hosts more resistant to their contemporary than past and future parasites (fluctuating selection dynamics). Fluctuating selection dynamics, which can potentially continue indefinitely, can be explained by fitness costs constraining the evolution of high levels of resistance in soil. These results suggest that rapid coevolution between bacteria and phage is likely to play a key role in structuring natural microbial communities.
Abstract: Torrado disease was first observed in protected tomato crops in the Murcia province of Spain in spring 2001, causing serious concern to regional tomato producers. The disease-causing agent was initially identified as a picorna-like bipartite plant RNA virus, now known as Tomato torrado virus (ToTV), but several additional torradoviruses inducing similar disease symptoms have been described more recently. We studied the incidence of torradoviruses between 2005 and 2008 in two parts of Murcia (Spain) where tomato crops are grown commercially. We also analysed the potential association among ToTV, Pepino mosaic virus (PepMV) and Tomato chlorosis virus (ToCV) in samples showing torrado symptoms of varying severity. ToTV was the only torradovirus found in the samples (predominantly as single infections), but double and triple infections comprising ToTV, PepMV and/or ToCV were also detected. There was no evidence of a specific association among the viruses as the frequencies of mixed infections did not deviate from those expected to occur by chance. Statistical analysis of the potential association between torrado symptoms and the type of infection (single or multiple) was inconclusive. To determine whether co-infections with ToTV and PepMV have any marked influence on the torrado disease, we analysed torrado symptom severity and virus accumulation in tomato plants experimentally infected with ToTV-CE, PepMV-Sp13 and PepMV-PS5 in single and mixed infections. The severity of the torrado symptoms was not affected by the presence of PepMV. In single infections, the ToTV titre remained very low, reaching its maximum in the early stages of infection and declining rapidly thereafter, whereas the disease symptoms became more severe over the same timescale. In mixed infections, the accumulation of both ToTV and PepMV was altered with respect to single infections, and the magnitude of this alteration appeared to be virus and strain specific. Therefore, ToTV and PepMV mixed infections may modulate the epidemiology of both viruses in a complex way by altering virus fitness. The impact of our studies on efforts to track and prevent the spread of torrado disease is discussed.
Abstract: Pepino mosaic virus (PepMV) is an emerging pathogen that causes severe economic losses in tomato crops (Solanum lycopersicum L.) in the Northern hemisphere, despite persistent attempts of control. In fact, it is considered one of the most significant viral diseases for tomato production worldwide, and it may constitute a good model for the analysis of virus emergence in crops. We have combined a population genetics approach with an analysis of in planta properties of virus strains to explain an observed epidemiological pattern. Hybridization analysis showed that PepMV populations are composed of isolates of two types (PepMV-CH2 and PepMV-EU) that cocirculate. The CH2 type isolates are predominant; however, EU isolates have not been displaced but persist mainly in mixed infections. Two molecularly cloned isolates belonging to each type have been used to examine the dynamics of in planta single infections and coinfection, revealing that the CH2 type has a higher fitness than the EU type. Coinfections expand the range of susceptible hosts, and coinfected plants remain symptomless several weeks after infection, so a potentially important problem for disease prevention and management. These results provide an explanation of the observed epidemiological pattern in terms of genetic and ecological interactions among the different viral strains. Thus, mixed infections appear to be contributing to shaping the genetic structure and dynamics of PepMV populations.
Abstract: Abstract Plant viruses are important agricultural pathogens, and are responsible for a significant number of commercially relevant plant diseases. There are very few efficient control measures for viral diseases, but the use of genetic resistance appears to be the most promising strategy, often conferring effective protection without additional costs or labour during the growing season, and without damaging the environment. Sources of virus resistance have been identified for most crop species, and many resistant cultivars are already commercially available and of widespread cultivation; however, much remains to be learned about genetic resistance. This review article considers three main aspects that require intense investigation. First, we review the identification of sources of resistance and how plant breeders and pathologists have focused on aspects of the breeding process particularly relevant to viruses, such as germplasm screening and the dissection of resistance phenotypes. Second, we review how molecular mechanisms controlling resistance have been unravelled, looking at case studies where resistance mechanisms are now understood in detail for each stage of the infection cycle. Third, we turn to the durability of resistance in a global context, examining factors that influence durability and how this can be predicted. We conclude with a short discussion of the technological and scientific opportunities provided by recent advances in the field.
Abstract: BACKGROUND: Melon (Cucumis melo L.) is one of the most important fleshy fruits for fresh consumption. Despite this, few genomic resources exist for this species. To facilitate the discovery of genes involved in essential traits, such as fruit development, fruit maturation and disease resistance, and to speed up the process of breeding new and better adapted melon varieties, we have produced a large collection of expressed sequence tags (ESTs) from eight normalized cDNA libraries from different tissues in different physiological conditions. RESULTS: We determined over 30,000 ESTs that were clustered into 16,637 non-redundant sequences or unigenes, comprising 6,023 tentative consensus sequences (contigs) and 10,614 unclustered sequences (singletons). Many potential molecular markers were identified in the melon dataset: 1,052 potential simple sequence repeats (SSRs) and 356 single nucleotide polymorphisms (SNPs) were found. Sixty-nine percent of the melon unigenes showed a significant similarity with proteins in databases. Functional classification of the unigenes was carried out following the Gene Ontology scheme. In total, 9,402 unigenes were mapped to one or more ontology. Remarkably, the distributions of melon and Arabidopsis unigenes followed similar tendencies, suggesting that the melon dataset is representative of the whole melon transcriptome. Bioinformatic analyses primarily focused on potential precursors of melon micro RNAs (miRNAs) in the melon dataset, but many other genes potentially controlling disease resistance and fruit quality traits were also identified. Patterns of transcript accumulation were characterised by Real-Time-qPCR for 20 of these genes. CONCLUSION: The collection of ESTs characterised here represents a substantial increase on the genetic information available for melon. A database (MELOGEN) which contains all EST sequences, contig images and several tools for analysis and data mining has been created. This set of sequences constitutes also the basis for an oligo-based microarray for melon that is being used in experiments to further analyse the melon transcriptome.
Notes: Gonzalez-Ibeas, Daniel Blanca, Jose Roig, Cristina Gonzalez-To, Mireia Pico, Belen Truniger, Veronica Gomez, Pedro Deleu, Wim Cano-Delgado, Ana Arus, Pere Nuez, Fernando Garcia-Mas, Jordi Puigdomenech, Pere Aranda, Miguel A Research Support, Non-U.S. Gov't England BMC genomics BMC Genomics. 2007 Sep 3;8:306.
Abstract: Background: Translation initiation factors of the 4E and 4G protein families mediate resistance to several RNA plant viruses in the natural diversity of crops. Particularly, a single point mutation in melon eukaryotic translation initiation factor 4E ( eIF4E) controls resistance to Melon necrotic spot virus ( MNSV) in melon. Identification of allelic variants within natural populations by EcoTILLING has become a rapid genotype discovery method. Results: A collection of Cucumis spp. was characterised for susceptibility to MNSV and Cucumber vein yellowing virus ( CVYV) and used for the implementation of EcoTILLING to identify new allelic variants of eIF4E. A high conservation of eIF4E exonic regions was found, with six polymorphic sites identified out of EcoTILLING 113 accessions. Sequencing of regions surrounding polymorphisms revealed that all of them corresponded to silent nucleotide changes and just one to a non-silent change correlating with MNSV resistance. Except for the MNSV case, no correlation was found between variation of eIF4E and virus resistance, suggesting the implication of different and/or additional genes in previously identified resistance phenotypes. We have also characterized a new allele of eIF4E from Cucumis zeyheri, a wild relative of melon. Functional analyses suggested that this new eIF4E allele might be responsible for resistance to MNSV. Conclusion: This study shows the applicability of EcoTILLING in Cucumis spp., but given the conservation of eIF4E, new candidate genes should probably be considered to identify new sources of resistance to plant viruses. Part of the methodology described here could alternatively be used in TILLING experiments that serve to generate new eIF4E alleles.
Notes: 189KM Times Cited:28 Cited References Count:45
Abstract: Xylem ultrastructural modification and the possible participation of phenolic compounds in the natural defense or resistance mechanisms of olive plants infected with Verticillium dahliae Kleb. were studied. Microscopic study showed that the mycelium propagated and passed from one element to another through the pit. The formation of tyloses and aggregates contributed to obstruction of the xylem lumen. In vivo changes in the levels of these phenolic compounds in infected olive plants and their antifungal activity against Verticillium dahliae Kleb., as revealed by in vitro study, strongly suggest that they are involved in natural defense or resistance mechanims in this plant material, the most active being quercetin and luteolin aglycons, followed by rutin, oleuropein, luteolin-7-glucoside, tyrosol, p-coumaric acid, and catechin.
Abstract: Citrus peel. is rich in flavanone glycosides and polymethoxyflavones. In view of their importance for industrial application as well as for their pharmacological properties, their content was analyzed in the mature fruits of several Citrus paradisi (grapefruit) and Citrus sinensis, (orange) varieties, with a view to select the most interesting for isolation. The results shows that the Star Ruby grapefruit and the Sanguinelli orange stand out for their high contents of naringin and hesperidin, respectively. The presence of the polymethoxyflavones nobiletin, heptamethoxyflavone and tangeretin, could be ascertained in all the grapefruit varieties analysed. Higher polymethoxyflavone levels were recorded in orange, with Valencia Late showing the greatest nobiletin, sinensetin and tangeretin contents and Navelate the highest heptamethoxyflavone levels. An in vitro study revealed that these compounds acted as antifungal agents against Penicillium digitatum, the polymethoxyflavones being more active than the flavanones in this respect. The possible participation of these phenolic compounds in the defence mechanism of Citrus against P. digitatum is discussed. (c) 2005 Elsevier Ltd. All rights reserved.
Abstract: The phenolic composition of olive roots and stems was studied by high performance liquid chromatography-mass spectrometry. The in vivo levels of the principal phenolic compounds found in olive plants infected by Phytophthora megasperma Drechsler and Cylindrocarpon destructans (Zinssm.) Scholten differed from the levels observed in non-infected plants. When the antifungal activity of these compounds against both fungi was studied in vitro, the most active were quercetin and luteolin aglycons, followed by rutin, oleuropein, p-coumaric acid, luteolin-7-glucoside, tyrosol and catechin. Microscopic study showed that these phenolic compounds affected the growth, morphology and ultrastructure of the fungi. Taken together, these findings suggest that the phenolic compounds present in olive plants play an active role in the protection against pathogen attack. (c) 2007 Elsevier Ltd. All rights reserved.
Abstract: Some of the medicinal properties of lemons are due to the flavonoids they contain since they are involved in many biological activities and have many health-related functions. The levels of the principal flavanones and flavone found in different cultivars of Citrus limon. are analysed in an attempt to identify the most interesting as regards the content of such secondary compounds. The results show that the miniature fruits from cultivars Lisbon and Fino-49 are ideal for obtaining the flavanone hesperidin, while the mature fruits of cultivar Fino-49 and the leaves of cultivar Eureka are the most interesting for obtaining the flavone diosmin and the flavanone eriocitrin. (C) 2003 Elsevier Ltd. All rights reserved.
Abstract: Phytophthora citrophthora causes serious losses in Citrus fruits through brown rot lesion. The effect of infection with P. citrophthora on Citrus sinensis (cv. Valencia Late) fruits was studied, with particular reference to the levels of the flavanones hesperidin and isonaringin and the polymethoxyflavones sinensetin, nobiletin, tangeretin, and heptamethoxyflavone, because flavonoids are most probably involved as natural defense or resistance mechanisms in this genus. Changes in the levels of these flavonoids were detected after infection. The hesperidin and isonaringin contents fell by 13 and 67%, respectively, whereas the contents of their corresponding aglycons, hesperetin and naringenin, increased, suggesting the hydrolyzing effect of this fungus on the glycosylated flavanones. The heptamethoxyflavone, nobiletin, sinensetin, and tangeretin levels increased by 48, 28, 26, and 24%, respectively. The in vitro study revealed that these compounds acted as antifungal agents, the most active being the aglycons (naringenin and hesperetin), followed by the polymethoxyflavones and flavanone glycosides. The participation of these flavonoids in the defense mechanism of this Citrus species is discussed.
Abstract: This paper studies the effects of different concentrations of ethephon (an ethylene-releasing compound) on the level of the steroidal sapogenin, diosgenin, in callus cultures of Trigonella foenum-graecum. The results show that diosgenin synthesis and/or accumulation was stimulated by 5, 15, and 25 ppm ethephon. This was particularly true in the case of the 25 ppm treatment when an increase of 195% was observed. Concentrations of 50 ppm and 100 ppm reduced diosgenin levels. The following morphological and ultrastructural changes were observed in the callus cells of T. foenum-graecum treated with ethephon: increased cell diameter, decreased cell packing (for all concentrations assayed), increased cytoplasmatic density (25 ppm treatment) and alteration of the membrane structures (50 and 100 ppm). (C) 2002 Published by Elsevier Science Ltd.
Notes: 536GR Times Cited:2 Cited References Count:31
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