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At least 73 records · Page 4Linked to original sources
PubMed2002

Whiteflies (Bemisia tabaci) issued from eggs bombarded with infectious DNA clones of Tomato yellow leaf curl virus from Israel (TYLCV) are able to infect tomato plants.

We have reported previously that Tomato yellow leaf curl virus from Israel (TYLCV) penetrates the reproductive system of its vector, the whitefly Bemisia tabaci biotype B, and may be transmitted to progeny. In order to mimic this phenomenon and to understand how TYLCV accompanies the development of the insect, we have bombarded B. tabaci eggs with an infectious DNA clone of TYLCV. After a linear full-length genomic copy of TYLCV DNA was delivered to eggs, the DpnI-sensitive DNA became circular and DpnI resistant. When a dimeric copy of TYLCV DNA was delivered to eggs, the viral DNA was detected in all the whitefly developmental stages. Adult insects that developed from the treated eggs were able to infect tomato test plants with variable frequency. Viral DNA was detected in the progeny of whiteflies that developed from eggs bombarded with TYLCV. Similarly, when insect eggs were bombarded with a dimeric copy of an infectious clone of the genome of Tomato yellow leaf curl virus from Sardinia, Italy (TYLCSV), adults that eclosed from the treated eggs were able to infect tomato test plants.

Animals↗
PubMed2005

Calmodulin-like proteins from Arabidopsis and tomato are involved in host defense against Pseudomonas syringae pv. tomato.

Complex signal transduction pathways underlie the myriad plant responses to attack by pathogens. Ca(2+) is a universal second messenger in eukaryotes that modulates various signal transduction pathways through stimulus-specific changes in its intracellular concentration. Ca(2+)-binding proteins such as calmodulin (CaM) detect Ca(2+) signals and regulate downstream targets as part of a coordinated cellular response to a given stimulus. Here we report the characterization of a tomato gene (APR134) encoding a CaM-related protein that is induced in disease-resistant leaves in response to attack by Pseudomonas syringae pv. tomato. We show that suppression of APR134 gene expression in tomato (Solanum lycopersicum), using virus-induced gene silencing (VIGS), compromises the plant's immune response. We isolated APR134-like genes from Arabidopsis, termed CML42 and CML43, to investigate whether they serve a functionally similar role. Gene expression analysis revealed that CML43 is rapidly induced in disease-resistant Arabidopsis leaves following inoculation with Pseudomonas syringae pv. tomato. Overexpression of CML43 in Arabidopsis accelerated the hypersensitive response. Recombinant APR134, CML42, and CML43 proteins all bind Ca(2+ )in vitro. Collectively, our data support a role for CML43, and APR134 as important mediators of Ca(2+)-dependent signals during the plant immune response to bacterial pathogens.

Amino Acid Sequence↗
PubMed2005

Nitric oxide and hydrogen peroxide in tomato resistance. Nitric oxide modulates hydrogen peroxide level in o-hydroxyethylorutin-induced resistance to Botrytis cinerea in tomato.

Nitric oxide (NO) has been postulated to be required, together with reactive oxygen species (ROS), for activation of disease resistance reactions of plants to infection with a pathogen or elicitor treatment. However, biochemical mechanisms by which ROS and NO participate in these reactions are still under intensive study and controversial debate. We previously demonstrated that o-hydroxyethylorutin when applied on tomato leaves (Lycopersicon esculentum Mill. cv. "Perkoz") restricted Botrytis cinerea infection development. In this research we investigated ROS and NO generation in tomato plants treated with o-hydroxyethylorutin, non-treated and infected ones. The NO content was enhanced or decreased in the studied plants by supplying them with NO generator-SNP or scavenger-cPTIO. NO detection was carried out using diaminofluorescein diacetate (DAF-DA) in conjunction with confocal laser scanning microscopy. The influence of elevated and decreased levels of NO on B. cinerea infection development and ROS generation was studied. The elevated NO concentration in tomato leaves strongly decreased hydrogen peroxide concentration without affecting other studied ROS (superoxide anion and hydroxyl radical) levels. H2O2 concentrations in NO-supplied leaves were low regardless of further treatment of tomato leaves with o-hydroxyethylorutin or inoculation with B. cinerea. The low H2O2 concentration coincided with quick and severe infection development in NO-supplied leaves. As activities of enzymes generating (SOD EC 1.15.1.1)) and removing (APX EC 1.11.1.11, CAT EC 1.11.1.6) H2O2 were unchanged in the studied plants, the decrease in H2O2 concentration was probably due to a direct NO-H2O2 interaction.

Botrytis↗
PubMed2004

Safety evaluation of a natural tomato oleoresin extract derived from food-processing tomatoes.

Experimental and epidemiological studies indicate that consumption of tomato products containing high amounts of lycopene is associated with lowered cancer risk. The protective effects of lycopene may be related to its antioxidant potential. Lycopene has been demonstrated to inhibit oxidation. A proprietary, natural tomato oleoresin extract (NTOE), is a purified tomato oleoresin containing 6% lycopene produced from tomatoes. NTOE was evaluated for toxicological effects, and found the 50% lethal dose (LD(50)), derived from the acute oral toxicity study, was greater than 5000 mg/kg body weight. The no-observed-adverse-effect level (NOAEL) derived from the 13-week study was 4500 mg/kg/day. Acute dermal toxicity study of NTOE found no toxicity at 2000 mg/kg body weight. NTOE lacked dermal irritation in the rabbit model, but was found to have moderate eye-irritant capabilities. NTOE tested at 5% (w/w) in petroleum jelly was a moderate sensitizer in the guinea pig model. There was no evidence of mutagenic potential up to 5000 microg/plate, as determined by the Ames assay. These results demonstrate the inability of NTOE to produce oral, dermal or mutagenic toxicity in animal models at doses greater than 300 times the normal human consumption of lycopene. Consumption analysis of lycopene-containing foods estimated mean daily intake of lycopene at 8.2mg/day.

Administration, Cutaneous↗
PubMed2003

Virulence systems of Pseudomonas syringae pv. tomato promote bacterial speck disease in tomato by targeting the jasmonate signaling pathway.

Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) causes bacterial speck disease on tomato. The pathogenicity of Pst DC3000 depends on both the type III secretion system that delivers virulence effector proteins into host cells and the phytotoxin coronatine (COR), which is thought to mimic the action of the plant hormone jasmonic acid (JA). We found that a JA-insensitive mutant (jai1) of tomato was unresponsive to COR and highly resistant to Pst DC3000, whereas host genotypes that are defective in JA biosynthesis were as susceptible to Pst DC3000 as wild-type (WT) plants. Treatment of WT plants with exogenous methyl-JA (MeJA) complemented the virulence defect of a bacterial mutant deficient in COR production, but not a mutant defective in the type III secretion system. Analysis of host gene expression using cDNA microarrays revealed that COR works through Jai1 to induce the massive expression of JA and wound response genes that have been implicated in defense against herbivores. Concomitant with the induction of JA and wound response genes, the type III secretion system and COR repressed the expression of pathogenesis-related (PR) genes in Pst DC3000-infected WT plants. Resistance of jai1 plants to Pst DC3000 was correlated with a high level of PR gene expression and reduced expression of JA/wound response genes. These results indicate that COR promotes bacterial virulence by activating the host's JA signaling pathway, and further suggest that the type III secretion system might also modify host defense by targeting the JA signaling pathway in susceptible tomato plants.

Amino Acids↗
PubMed2006

Effects of Galanthus nivalis agglutinin (GNA) expressed in tomato leaves on larvae of the tomato moth Lacanobia oleracea (Lepidoptera: Noctuidae) and the effect of GNA on the development of the endoparasitoid Meteorus gyrator (Hymenoptera: Braconidae).

The effect of ingestion of transgenic tomato leaves expressing the plant lectin Galanthus nivalis agglutinin (GNA) on development of larvae of Lacanobia oleracea (Linnaeus) was studied under laboratory conditions. When L. oleracea larvae were fed on tomato line 14.1H, expressing approximately 2.0% GNA, significant increases in the mean larval weight and in the amount of food consumed were found. This resulted in an overall reduction in the mean development time to the pupal stage of approximately 7 days. A significant increase in the percentage survival to the adult moth was also recorded when newly hatched larvae were reared on transgenic tomato leaves (72%) compared to larvae reared on untransformed leaves (40%). The effects of ingestion of GNA by L. oleracea larvae, via artificial diet or the leaves of transgenic tomato or potato plants, on the subsequent development of its solitary endoparasitoid Meteorus gyrator (Thunberg) was also studied. No significant effects on the life cycle parameters of M. gyrator developing in L. oleracea fed on GNA-containing diets were observed. Experiments with transgenic potato plants indicated that the stadium of the host larvae at parasitism had a greater influence on M. gyrator development than the presence of GNA. Potential GNA-binding glycoproteins were detected in the gut and body tissues of larval M. gyrator. Despite detection in host tissues, GNA could not be detected in adult M. gyrator and therefore it is likely that at the time of pupation M. gyrator are able to void the GNA in the meconial pellet.

Animals↗
PubMed2006

Ovipositional preferences, damage thresholds, and detection of the tomato-potato psyllid Bactericera cockerelli (Homoptera: Psyllidae) on selected tomato accessions.

The tomato-potato psyllid Bactericera [Paratrioza] cockerelli (Sulc) has recently caused losses exceeding 50% on fresh market tomatoes in California and Baja, Mexico by injecting a toxin that results in a condition known as 'psyllid yellows'. The objectives of this study were to: (i) document oviposition preferences on a range of tomato cultivars; (ii) determine threshold levels for psyllid densities that would cause psyllid yellows on tomatoes within the first three weeks following transplanting; and (iii) identify the most important 'psyllid yellows' symptoms that might be used in surveying and monitoring for this pest. Plant lines tested included the commonly-planted commercial cultivars 'Shady Lady' and 'QualiT 21', an older, previously commercial cultivar '7718 VFN', a common cultivar planted by consumers 'Yellow Pear', and a wild type plant accession, PI 134417. When given a choice, psyllids significantly preferred 'Yellow Pear' and avoided PI 134417 for oviposition. Under no-choice conditions psyllids laid significantly fewer eggs on PI 134417, but all the other plant lines were equally good substrates for laying eggs. Thus, oviposition preference is not likely to provide a functional management strategy in large plantings. On 'Shady Lady', psyllids preferred to oviposit on plants already infested with adults. On both 'Shady Lady' and '7718 VFN' oviposition was significantly greater on plants previously infested by nymphs as compared to uninfested control plants. This suggests that, at least for some cultivars, there is a physiological change in plant attractiveness following psyllid feeding. 'Yellow Pear' and 'QualiT 21' were relatively tolerant of psyllids, requiring 18 nymphs per plant to produce the disease symptoms. Only eight nymphs per plant were needed on 'Shady Lady' and '7718 VFN'. For all cultivars, the pest density showed strong correlations with measurements such as the number of yellowing leaves and leaflets and distorted leaves, which were as good as or better than the first factor extracted from principal component analysis. Therefore, such measurements have the potential to simplify field surveys.

Analysis of Variance↗
PubMed2004

A new quality parameter in tomato and tomato products: ergosterol.

The poor precision of the "percentage of discarded fruits" and "Howard mold count" methods has increased the importance of ergosterol for the microbiological quality evaluation of tomato and tomato products. Ergosterol, a constituent of the cell wall of some important vegetable parasites, such as molds, has been recently recognized as a potential objective parameter useful for the characterization of the quality of processing tomatoes. Thus, 15 mg of ergosterol/kg total solids has been stated as an acceptability maximum limit of tomato products.

Ergosterol↗
PubMed2006

Transgenic flavonoid tomato intake reduces C-reactive protein in human C-reactive protein transgenic mice more than wild-type tomato.

The increased consumption of fruits and vegetables is associated with reduced cardiovascular disease. The molecular basis of this health effect is not fully understood, yet dietary flavonoids are thought to play an important role. Genetic engineering has enabled us to overexpress specific flavonoids (flavones and flavonols) in tomato fruit. Human C-reactive protein transgenic (CRPtg) mice express markers of cardiovascular risk that allow us to study of the putative health effects of wild-type tomato (wtTom) and flavonoid-enriched tomato (flTom). In this study, we analyzed whether consumption of wtTom, at a dose achievable with a human diet, has beneficial effects on cardiovascular risk markers and whether flTom may enhance such effects. CRPtg mice were fed a diet containing 4 g/kg wtTom, flTom peel, vehicle, or 1 g/kg fenofibrate, which reportedly reduces cardiovascular risk, for 7 wk. Markers of general health (bodyweight, food intake, and plasma alanine aminotransferase activities) and of cardiovascular risk (plasma CRP, fibrinogen, E-selectin, and cholesterol levels) were analyzed. All groups had comparable food intakes and body-weight gains. Plasma alanine aminotransferase activities increased significantly in vehicle and fenofibrate-treated mice. Compared with baseline, wtTom and flTom significantly reduced basal human CRP concentrations by 43 and 56%, respectively. The CRP-lowering effect of flTom significantly exceeded that of wtTom. The effects of flTom on CRP were reversed within a 2-wk washout period. WtTom and flTom did not affect fibrinogen, but comparably repressed E-selectin expression and upregulated HDL cholesterol. Tomato peel consumption improved cardiovascular risk factors in CRPtg mice, a beneficial effect that was further enhanced by enrichment of the flavonoid content.

Alanine Transaminase↗
PubMed1993

Two amino acid substitutions in the tomato mosaic virus 30-kilodalton movement protein confer the ability to overcome the Tm-2(2) resistance gene in the tomato.

The Tm-2(2) resistance gene is used in most commercial tomato cultivars for protection against infection with tobacco mosaic virus and its close relative tomato mosaic virus (ToMV). To study the mechanism of this resistance gene, cDNA clones encompassing the complete genome of a ToMV strain (ToMV-2(2)) that was able to break the Tm-2(2) resistance were generated. Chimeric full-length viral cDNA clones were constructed under the control of the cauliflower mosaic virus 35S RNA promoter, combining parts of the wild-type virus and ToMV-2(2). Using these clones in cDNA infection experiments, we showed that the 30-kDa movement protein of ToMV-2(2) is responsible for overcoming the Tm-2(2) resistance gene in the tomato. DNA sequence analysis revealed four amino acid exchanges between the 30-kDa proteins from wild-type ToMV and ToMV-2(2), Lys-130 to Glu, Gly-184 to Glu, Ser-238 to Arg, and Lys-244 to Glu. To clarify the involvement of the altered amino acid residues in the resistance-breaking properties of the ToMV-2(2) movement protein, different combinations of these amino acid exchanges were introduced in the genome of wild-type ToMV. Only one mutant strain which contained two amino acid substitutions, Arg-238 and Glu-244, was able to multiply in Tm-2(2) tomato plants. Both amino acid exchanges are found within the carboxy-terminal region of the movement protein, which displays a high variability among different tobamoviruses and has been shown to be dispensable for virus transport in tobacco plants. These observations suggest that the resistance conferred by the Tm-2(2) gene against ToMV depends on specific recognition events in this host-pathogen interaction rather than interfering with fundamental functions of the 30-kDa protein.

Base Sequence↗
PubMed2002

A natural recombinant between the geminiviruses Tomato yellow leaf curl Sardinia virus and Tomato yellow leaf curl virus exhibits a novel pathogenic phenotype and is becoming prevalent in Spanish populations.

This work provides evidence of the significant contribution of recombination to the genetic diversification of emerging begomovirus populations. In southern Spain, Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are distinct geminivirus species that coexist in the field and contribute to the tomato yellow leaf curl disease epidemic. A natural recombinant between TYLCSV and TYLCV has been detected and an infectious clone of a recombinant isolate (ES421/99) was obtained and characterized. Analysis of its genome showed that the recombination sites are located in the intergenic region in which a conserved stem-loop structure occurs and at the 3'-end of the replication enhancer protein open reading frame. ES421/99 exhibited a novel pathogenic phenotype that might provide it with a selective advantage over the parental genotypes. This agrees with results from field studies which revealed that the recombinant strain is becoming prevalent in the region in which it was detected.

Base Sequence↗
PubMed1991

Identification of the viroid-induced tomato pathogenesis-related (PR) protein P23 as the thaumatin-like tomato protein NP24 associated with osmotic stress.

P23, a 23 kDa pathogenesis-related (PR) protein, was purified from citrus exocortis viroid (CEVd)-infected tomato leaves. Partial amino acid sequencing of this protein including the N-terminal and nine additional tryptic fragments covering about 50% of its primary structure revealed extensive homologies to the members of the family of plant thaumatin-like proteins. Sequence alignment revealed that tomato P23 is the previously described NP24 protein found to be associated to osmotic stress in tomato. In view of this fact the possible role of pathogenesis-related P23 protein as a component of a general mechanism of response of the plant is discussed.

Amino Acid Sequence↗
PubMed1993

Genetic characterization of the Pto locus of tomato: semi-dominance and cosegregation of resistance to Pseudomonas syringae pathovar tomato and sensitivity to the insecticide Fenthion.

The Pto locus governs resistance to bacterial speck disease in tomato caused by race 0 strains of Pseudomonas syringae pathovar tomato (Pst). Large populations segregating for the Pto locus were generated and genetically characterized. Analysis of the locus has revealed that Pto acts in a semi-dominant manner and cosegegrates with sensitivity to an organophosphorous insecticide, Fenthion, suggesting that Pto may be a complex locus responsible for both phenotypes. We have redefined its map position on chromosome five of the classical genetic map and assigned its position on the molecular map, thus facilitating the alignment of the two genetic maps of the short arm of chromosome five of tomato. Furthermore, we have screened random amplified polymorphic (RAPD) markers for their ability to differentiate near-isogenic lines that differ only with respect to Pto and have identified and mapped seven of these markers. Our results suggest that Pto may be located in a euchromatic region on chromosome five which will be advantageous for the cloning of this locus by one of several molecular strategies.

Base Sequence↗
PubMed2002

Induction of phenylpropanoid metabolism by Pseudomonas fluorescens against tomato spotted wilt virus in tomato.

Pseudomonas fluorescens (two native strains, one collection strain and their strain mixtures in all possible combinations) when applied through seed, seedling dip, soil and on leaf significantly reduced the tomato spotted wilt virus (TSWV) disease. In P. fluorescens-treated plants, the peroxidase and phenylalanine ammonia-lyase activity increased. Accumulation of phenolic compounds and lignin were shown to be increased in the P. fluorescens-treated plants. Isoperoxidase native PAGE indicated that the peroxidase isoforms in tomato plants induced by fluorescent pseudomonads were different from the control plants; this suggests that the general phenylpropanoid pathway is probably stimulated in tomato plants treated which in turn led to significant reduction in TSWV.

Electrophoresis, Polyacrylamide Gel↗
PubMed1984

Effect of tiazofurin on tomato plants infected with tomato spotted wilt virus.

Tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide) was examined for its activity against tomato-spotted wilt virus (TSWV) in tomato plants. Solutions containing 50, 100, 200, 400 and 800 mg/l of the drug were sprayed onto the leaves. The results showed that 100 and 200 mg/l were the most efficient concentrations to suppress TSWV infection, thereby delaying the appearance of systemic symptoms. The drug was more effective in controlling TSWV infection when applied after than before virus inoculation. The results suggest that tiazofurin can be used as an efficient antiviral drug in the treatment of TSWV-infected tomato plants.

Antiviral Agents↗
PubMed2005

Expressed sequence tags from the laboratory-grown miniature tomato (Lycopersicon esculentum) cultivar Micro-Tom and mining for single nucleotide polymorphisms and insertions/deletions in tomato cultivars.

Laboratory-grown miniature tomato (Lycopersicon esculentum) cultivar Micro-Tom has attracted attention as a host for functional genomics research. In this study, we generated 35,824 expressed sequence tags (ESTs) from leaves and fruits of Micro-Tom. The ESTs comprised 10,287 unigenes (5007 contigs and 5280 singletons), including 1858 novel tomato unigenes. Of the 18 unigenes that shared strong homology with tobacco chloroplast genome sequences, one unigene was likely derived from polyadenylated transcripts of the atpH gene. Interestingly, ESTs for vacuolar invertase, pectate lyase and alcohol acyl transferase were underrepresented in the Micro-Tom data set. From all of the ESTs, we mined 2039 candidate single nucleotide polymorphisms (SNPs) and 121 candidate insertions and deletions (indels) based on homology with four tomato inbred lines, E6203, R11-13, Rio Grande PtoR and R11-12, and a wild relative, L. pennellii TA56, for which sequence data was publicly available with more than 5000 entries. Direct genome sequencing of several SNP or indel sites in Micro-Tom and L. esculentum E6203 suggested that more than 69% of the candidate sites were truly polymorphic, making them useful for the preparation of DNA markers.

DNA, Complementary↗
PubMed1997

Developmental regulation of two tomato lipoxygenase promoters in transgenic tobacco and tomato.

Two lipoxygenase (LOX) genes (tomloxA and tomloxB) are expressed in ripening tomato fruit, and tomloxA is also expressed in germinating seedlings. The 5'-upstream regions of these genes were isolated to study the regulatory elements involved in coordinating tomlox gene expression. Sequence analysis of the promoters did not reveal any previously characterized regulatory elements except for TATA and CAAT boxes. However, the sequence motif GATAcAnnAAtnTGATG was found in both promoters. Chimeric gene fusions of each tomlox promoter with the beta-glucuronidase reporter gene (gus) were introduced into tobacco and tomato plants via Agrobacterium-mediated transformation. GUS activity in tomloxA-gus plants during seed germination peaked at day 5 and was enhanced by methyl jasmonate (MeJa) treatment. No GUS activity was detected in tomloxB-gus seedlings. Neither wounding nor abscisic acid (ABA) treatment of transgenic seedlings modified the activity of either promoter. During fruit development, GUS expression in tomloxA-gus tobacco fruit increased 5 days after anthesis (DAA) and peaked at 20 DAA. In tomloxB-gus tobacco fruit, GUS activity increased at 10 DAA and peaked at 20 DAA. In transgenic tomato fruit, tomloxA-gus expression was localized to the outer pericarp during fruit ripening, while tomloxB-gus expression was localized in the outer pericarp and columella. These data demonstrate that the promoter regions used in these experiments contain cis-acting regulatory elements required for proper regulation of tomlox expression during development and for MeJa-responsiveness.

Abscisic Acid↗
PubMed2002

New pollen-specific receptor kinases identified in tomato, maize and Arabidopsis: the tomato kinases show overlapping but distinct localization patterns on pollen tubes.

We previously characterized LePRK1 and LePRK2, pollen-specific receptor kinases from tomato (Muschietti et al., 1998). Here we identify a similar receptor kinase from maize, ZmPRK1, that is also specifically expressed late in pollen development, and a third pollen receptor kinase from tomato, LePRK3. LePRK3 is less similar to LePRK1 and LePRK2 than either is to each other. We used immunolocalization to show that all three LePRKs localize to the pollen tube wall, in partially overlapping but distinct patterns. We used RT-PCR and degenerate primers to clone homologues of the tomato kinases from other Solanaceae. We deduced features diagnostic of pollen receptor kinases and used these criteria to identify family members in the Arabidopsis database. RT-PCR confirmed pollen expression for five of these Arabidopsis candidates; two of these are clearly homologues of LePRK3. Our results reveal the existence of a distinct pollen-specific receptor kinase gene family whose members are likely to be involved in perceiving extracellular cues during pollen tube growth.

Amino Acid Sequence↗