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PubMed1971

Isolation of microbodies from plant tissues.

Specialized microbodies have previously been isolated and characterized from fatty seedling tissues (glyoxysomes) and leaves (leaf peroxisomes). We have now examined 11 other plant tissues, including tubers, fruits, roots, shoots, and petals, and find that all contain particulate catalase, a distinctive common enzyme component of microbodies. On linear sucrose gradients the catalase activity peaks sharply at a higher equilibrium density (1.20 to 1.25 gram per cm(3) in the various tissues) than the mitochondria (1.17 to 1.20). Only small amounts of protein are recovered in the fractions containing catalase, although a definite band is visible in preparations from some tissues, e.g., potato. As in the preparations from castor bean endosperm and spinach leaves for which comparable data are provided, the distribution of glycolate oxidase and uricase follows closely that of catalase on the gradients. The preparations from potato lack glyoxylate reductase and the transaminases, typical enzymes of leaf peroxisomes, and the distinctive enzymes of glyoxysomes are missing. Nonspecialized microbodies with limited enzyme composition can thus be isolated from a variety of plant tissues.

Journal Article↗
PubMed2005

Resistance among Escherichia coli to sulphonamides and other antimicrobials now little used in man.

OBJECTIVES: We investigated whether sulphonamide resistance in Escherichia coli remained prevalent in 2004, 9 years since the formal introduction of a UK prescribing restriction on co-trimoxazole. Resistance to other agents no longer in common use was also examined. METHODS: Consecutive urinary E. coli isolates were obtained at the diagnostic microbiology laboratory of the Royal London Hospital from January to March 2004. The presence of the sulphonamide resistance genes, sul1, sul2 and sul3, and the class I integrase gene, int1, were determined by PCR. RESULTS: Of the 391 E. coli isolates recovered in 2004, 45.5% were sulphonamide-resistant compared with 46.0% in 1999 and 39.7% in 1991. The sul2 gene remained the most prevalent sulphonamide resistance determinant, present in 81% of resistant isolates in 2004 compared with 79% and 67% in 1999 and 1991, respectively; 28% of resistant isolates carried both sul1 and sul2 genes; sul3 was not found. Resistance to streptomycin also remained common, whereas resistance to chloramphenicol and kanamycin had decreased since 1999. CONCLUSION: Sulphonamide resistance in E. coli persists undiminished despite the prolonged withdrawal of this antibiotic in the UK; resistance to streptomycin also seems stable whilst that to chloramphenicol and kanamycin is declining.

Anti-Bacterial Agents↗
PubMed1998

CD38+ CD45RB(low) CD4+ T cells: a population of T cells with immune regulatory activities in vitro.

An antibody reactive with CD38 revealed both phenotypic and functional heterogeneity amongst CD45RB(low) cells. Functional analysis of the CD38+ and CD38- fractions showed that the latter contained T cells which responded to recall antigens and produced high levels of cytokine in response to polyclonal stimulation. In contrast, the CD38+ population failed to proliferate or to produce detectable levels of cytokines. Despite appearing unresponsive, the CD38+ population significantly inhibited anti-CD3-induced proliferation and cytokine secretion by the reciprocal CD38- population. Immune suppression required stimulation through the TCR and was dependent on a physical interaction between regulatory and responding CD4+ populations. It did not involve killing of the responding T cells or secretion of IL-10 or TGF-beta. Despite some similarities there is no direct correlation between the in vitro suppression characteristic of the CD38+ CD45RB(low) subset and in vivo suppression which has been shown to be mediated by unseparated CD45RB(low) CD4+ T cells. However, these results demonstrate that two functionally distinct subsets of T cells reside within the antigen-exposed or CD45RB(low) CD4+ T cell population and are thus generated in vivo: (1) conventional memory T cells which proliferate and secrete cytokines in response to activation and (2) a population of regulatory T cells which inhibit T cell activation in vitro. Antibodies reactive with CD38 may provide a useful tool with which to study the role of these T cell subsets in the induction and regulation of the immune response.

ADP-ribosyl Cyclase↗
PubMed1990

Cloning and expression of rat histidase. Homology to two bacterial histidases and four phenylalanine ammonia-lyases.

Histidase (histidine ammonia-lyase, EC 4.3.1.3) catalyzes the deamination of histidine to urocanic acid. Apart from phenylalanine ammonia-lyase, which is not expressed in animals, histidase is the only enzyme known to have a dehydroalanine residue in its active site. The amino site precursor and the mechanism of formation of dehydroalanine are not known. As an initial step to determining the precursor of dehydroalanine in histidase, we have isolated a functional cDNA clone for histidase from a rat liver cDNA library using an affinity-purified antiserum. The 2.2-kilobase cDNA has a 1,971-base pair open reading frame coding for a 657-amino acid polypeptide with a predicted molecular mass of 72,165 Da. The cDNA has a rare polyadenylation signal (AAUACA) that appears to inefficiently direct polyadenylation in transfected COS monkey kidney cells. Conversion of this sequence to the consensus polyadenylation signal (AAUAAA) resulted in increased levels of stable mRNA. COS cells transfected with a histidase expression vector produce active histidase. The formation of active histidase in cells that have no endogenous histidase activity suggests either that the requisite modifying enzyme is present in these cells or that the dehydroalanine residue forms by an autocatalytic mechanism. Rat histidase was found to have 41 and 43% amino acid identity to Pseudomonas putida and Bacillus subtilis histidases, respectively. Phenylalanine ammonia-lyases from parsley, kidney bean, and two yeast strains were also found to have approximately 20% amino acid identity to rat histidase. On the basis of the similarity of function of histidase and phenylalanine ammonia-lyase, dehydroalanine at the active sites, and the sequence conservation over a large evolutionary distance (mammals, bacteria, yeast, and plants), we propose that the genes for histidase and phenylalanine ammonia-lyase have diverged from a common ancestral gene, of which the most conserved regions are likely to be involved in catalysis or dehydroalanine formation.

Amino Acid Sequence↗
PubMed1975

Resolution of proteases in the keratinolytic larvae of the webbing clothes moth.

The proteases of the larvae of the webbing clothes moth, Tineola bisselliella, were investigated because of this organism's phylogenetic rank as a member of the lower invertebrates, its unique position as one of the relatively few organisms that can digest keratin and its importance as a serious fabric pest. Both the number and nature of different proteolytic enzymes present were investigated and the various activities partially fractionated by ammonium sulphate precipitation and chromatography on DEAE-cellulose and Sephadex G200 columns. A complex mixture of peptidases and proteinases has been found in extracts of whole larvae and has been shown to be associated with the larval digestive tract. The proteinases include metal-chelator-sensitive proteinases (metalloproteinases) and serine proteinases but no SH-proteinases or acid proteinases. The serine proteinases include both trypsin-like and chymotrypsin-like activities. Four major and three minor anionic trypsin-like enzymes and a single major cationic trypsin-like enzyme have been detected. Only a single anionic chymotrypsin-like enzyme appears to be present. The trypsin-like enzymes are unaffected by the naturally occurring proteinase inhibitors, chicken ovomucoid, soybean trypsin inhibitor and lima bean trypsin inhibitor, while the chymotrypsin-like enzyme is inhibited by soybean trypsin inhibitor only. The enzymes resemble the serine proteinases from microorganisms in their pH stability. The peptidases include both aminopeptidase and carboxypeptidase activities and both are present in multiple forms. Sixteen aminopeptidase bands have been detected and all are present in individual larvae. They are not inhibited completely by reagents specific for any of the common active sites, and have different specificity requirements. Two carboxypeptidases have been detected on acrylamide gels and have been completely separated on DEAE-cellulose. No evidence could be found for the existence of any of these proteases as inactive precursors.

Aminopeptidases↗
PubMed2000

Nutritional and anti-nutritional composition of velvet bean: an under-utilized food legume in south India.

Four accessions of the under-utilized legume, velvet bean (Mucuna pruriens var. utilis (Wall. ex Wight) Bak. ex Burck), collected from three different locations of Western Ghats, South India were analysed for proximate composition, mineral profiles, the protein fractions, amino acid profiles of total seed protein, in vitro protein digestibility and certain anti-nutritional factors to determine their potential as an alternative source to alleviate protein-energy-malnutrition among the people of South India. The major findings of the study were as follows: crude protein ranged from 20.2-29.3%, crude lipid 6.3-7.4%, total dietary fibre 8.7-10.5%, ash 3.3-5.5% and carbohydrates 49.9-61.2%. The energy level of the seed (1562-1597 kJ 100 g-1 DM) was comparable with commonly consumed Indian pulses. Mineral profiles, viz. sodium, potassium, calcium, magnesium, phosphorus, iron, copper, zinc and manganese ranged from 43.1-150.1, 778.1-1846.0, 393.4-717.7, 174.9-387.6, 98.4-592.1, 10.8-15.0, 0.9-2.2, 5.0-10.9, 3.9-4.3 mg 100(-1) seed flour, respectively. The data on seed protein fractions revealed that the globulins constitute the major bulk of the seed protein as in most legumes. Profiles of amino acids of total seed proteins detected in the present study revealed that they contain relatively higher levels of all essential amino acids except threonine, leucine and lysine in black-coloured seed coat accessions and phenylalanine and tyrosine in white-coloured seed coat accession compared with the FAO/WHO (1991) requirement pattern. The in vitro protein digestibility of the legumes under study ranged from 72.4-76.9%. Anti-nutritional substances like total free phenolics, tannins, L-DOPA, trypsin inhibitor activity and phytohaemagglutinating activity also were investigated. The detected anti-nutritional factors probably have little nutritional significance if the beans are properly processed.

Amino Acids↗
PubMed1997

Solubilization and Separation of a Plant Plasma Membrane NADPH-O2- Synthase from Other NAD(P)H Oxidoreductases.

Solubilization and ion-exchange chromatography of plasma membrane proteins obtained from bean (Phaseolus vulgaris L.) seedlings resulted in a single NAD(P)H-O2--synthase protein peak. This enzyme showed a high preference toward NADPH as a substrate (reaction rate, 27.4 nmol O2- produced min-1 mg-1 protein), whereas NADH reactions ranged from 0 to maximally 15% of the NADPH reactions. The protein functions as an oxidase and it was clearly resolved from NAD(P)H dehydrogenases identified with commonly used strong oxidants (ferricyanide, cytochrome c, DCIP, and oxaloacetate). The involvement of peroxidases in O2- production is excluded on the basis of potassium-cyanide insensitivity and NADPH specificity. The NADPH oxidase is only moderately stimulated by flavins (1.5-fold with 25 [mu]M flavine adenine dinucleotide and 2.5-fold with 25 [mu]M flavin mononucleotide) and inhibited by 100 [mu]M p-chloromercuribenzenesulfonic acid, 200 [mu]M diphenyleneiodonium, 10 mM quinacrine, 40 mM pyridine, and 20 mM imidazole. The presence of flavins was demonstrated in the O2-synthase fraction, but no b-type cytochromes were detected. The effect of these inhibitors and the detection of flavins and cytochromes in the plant O2- synthase make it possible to compare this enzyme with the NADPH O2- synthase of animal neutrophil cells.

Journal Article↗
PubMed2007

Evaluation of six presumptive tests for blood, their specificity, sensitivity, and effect on high molecular-weight DNA.

Luminol, leuchomalachite green, phenolphthalein, Hemastix, Hemident, and Bluestar are all used as presumptive tests for blood. In this study, the tests were subjected to dilute blood (from 1:10,000 to 1:10,000,000), many common household substance, and chemicals. Samples were tested for DNA to determine whether the presumptive tests damaged or destroyed DNA. The DNA loci tested were D2S1338 and D19S433. Leuchomalachite green had a sensitivity of 1:10,000, while the remaining tests were able to detect blood to a dilution of 1:100,000. Substances tested include saliva, semen, potato, tomato, tomato sauce, tomato sauce with meat, red onion, red kidney bean, horseradish, 0.1 M ascorbic acid, 5% bleach, 10% cupric sulfate, 10% ferric sulfate, and 10% nickel chloride. Of all the substances tested, not one of the household items reacted with every test; however, the chemicals did. DNA was recovered and amplified from luminol, phenolphthalein, Hemastix, and Bluestar, but not from leuchomalachite green or Hemident.

Aniline Compounds↗
PubMedDate not supplied

Hyperhomocysteinemia is associated with low plasma pyridoxine levels in children with sickle cell disease.

Elevated plasma homocysteine levels have been shown to be a risk factor for endothelial cell damage and thrombosis, which are implicated in sickle cell disease (SCD)-related vaso-occlusion. The aim of this study was to determine the prevalence of hyperhomocysteinemia in SCD. Fasting and postmethionine load (PML) homocysteine, red cell folate, and the MTHFR C677T mutation were determined in 77 patients with SCD and 110 African-American controls. Plasma methylmalonic acid and pyridoxine levels were determined in 54 patients and all controls. For analysis, the subjects were divided into two age groups (2-10 years and 10.1-21 years). In both age groups, median PML homocysteine levels were significantly elevated in patients with SCD compared with controls. Fasting homocysteine levels were elevated in patients with SCD versus controls only in those older than 10 years. Hyperhomocysteinemia was noted in 38% of patients versus 7% in controls. Folate levels were higher among patients than controls and showed a significant negative correlation with PML homocysteine levels in patients with SCD. Pyridoxine levels in patients with SCD were significantly lower than in controls and showed a negative correlation with PML homocysteine levels. Among patients with SCD, pyridoxine deficiency was more common (62%) among those with hyperhomocysteinemia compared with those with normal homocysteine levels (30%). Homozygosity for the MTHFR C677T mutation was rare. These data suggest that children with SCD have significant hyperhomocysteinemia, associated with pyridoxine and relative folate deficiencies.

Adolescent↗
PubMed1986

Antihypertensive drugs inhibit hypertension-associated aortic DNA synthesis in the rat.

The effect of antihypertensive drug treatment on aortic DNA synthesis was examined in rats with two-kidney, one clip renal hypertension and in spontaneously hypertensive rats (SHR). In two-kidney, one clip hypertensive rats, hypertension developed over a 2-week period. Four days after clipping the renal artery, during the onset of hypertension, there was an increase in aortic DNA synthesis. Aortic DNA synthesis was also increased 3 weeks later, when hypertension had been established. Captopril, hydralazine, and verapamil were each able to prevent the increase in aortic DNA synthesis and the rise in blood pressure when given throughout the first 5 days of the developing phase of hypertension, or when given to rats with established hypertension. Drug treatment of sham-operated rats had no significant effect on DNA synthesis, although blood pressure was decreased. There were no differences in blood pressure or aortic DNA synthesis in 4-week-old SHR, as compared with age-matched Wistar-Kyoto (WKY) controls or normal Wistar rats. At 17 weeks of age, when hypertension was established, aortic DNA synthesis was significantly enhanced in the SHR. Captopril or hydralazine treatment was able to reduce blood pressure and DNA synthesis to levels seen in the WKY. At 21 weeks of age, DNA synthesis in the SHR had declined to the same levels as in the WKY. Captopril, hydralazine, and verapamil may have a common ability to reduce intracellular calcium and therefore inhibit DNA synthesis. In support of this, ouabain treatment, which increases intracellular calcium by inhibiting the Na+-K+ pump, produced a significant increase in the rate of DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Stimulation of de novo synthesis of L-phenylalanine ammonia-lyase in relation to phytoalexin accumulation in Colletotrichum lindemuthianum elicitor-treated cell suspension cultures of french bean (Phaseolus vulgaris).

(1) The regulation of the accumulation of the isoflavonoid-derived phytoalexin phaseollin in cell suspension cultures of Dwarf French Bean (Phaseolus vulgaris/ has been investigated. (2) An elicitor preparation from cell walls of Colletotrichum lindemuthianum, the causal agent of anthracnose disease of French bean, caused a marked accumulation of phaseollin in the cultures. The elicitor induced phaseollin accumulation to a level of 60% that obtained with the artificial elicitor autoclaved ribonuclease A and was maximally active at a concentration (weight basis) of at least 50 times lower than required for maximal response to ribonuclease. (3) Elicitor preparations from cell walls of Phytophthora megasperma var. sojae, a fungal pathogen of soybean, and Botrytis cinerea, the common grey mould, were much less effective than the C. lindemuthianum wall-released elicitor. (4) There was a marked but transient increase in the extractable activity of phenylalanine ammonia-lyase, the enzyme catalysing the first reaction in the biosynthesis of phaseollin from L-phenylalanine, in response to the elicitor from C. lindemuthianum. (5) Comparative density labelling with 2H from 2H2O indicated that the elicitor stimulates de novo synthesis of phenylalanine ammonie findings provide the basis of a scheme for elicitor induction of phytoalexin accumulation.

Ammonia-Lyases↗
PubMed2005

A provisional database for the silicon content of foods in the United Kingdom.

Si may play an important role in bone formation and connective tissue metabolism. Although biological interest in this element has recently increased, limited literature exists on the Si content of foods. To further our knowledge and understanding of the relationship between dietary Si and human health, a reliable food composition database, relevant for the UK population, is required. A total of 207 foods and beverages, commonly consumed in the UK, were analysed for Si content. Composite samples were analysed using inductively coupled plasma-optical emission spectrometry following microwave-assisted digestion with nitric acid and H(2)O(2). The highest concentrations of Si were found in cereals and cereal products, especially less refined cereals and oat-based products. Fruit and vegetables were highly variable sources of Si with substantial amounts present in Kenyan beans, French beans, runner beans, spinach, dried fruit, bananas and red lentils, but undetectable amounts in tomatoes, oranges and onions. Of the beverages, beer, a macerated whole-grain cereal product, contained the greatest level of Si, whilst drinking water was a variable source with some mineral waters relatively high in Si. The present study provides a provisional database for the Si content of UK foods, which will allow the estimation of dietary intakes of Si in the UK population and investigation into the role of dietary Si in human health.

Beverages↗
PubMed1998

Sensitization to green coffee beans and work-related allergic symptoms in coffee workers.

BACKGROUND: Occupational respiratory allergy to green coffee beans (GCB) and to castor beans (CB) was studied in 112 workers in a modern coffee manufacturing plant of Trieste (Italy), where the process is completely automatic, the environmental conditions are good and where exposure to CB can be considered absent because since 1970, only new sacks have been used for coffee transportation. METHODS: All subjects were interviewed by a trained doctor using a questionnaire to investigate allergic symptoms and predisposing factors. Sensitization to GCB and to common allergens (pollens, molds, house dust mites) were evaluated by the skin-prick test. The serum of subjects with a positive skin-prick test to CGB or who had symptoms at work was tested for specific IgE (RAST) for GCB and CB. Lung function was evaluated by a Ponigraph spirometer. RESULTS: Sensitization to GCB was found in 25.8% of green coffee workers (31 cases), in 2.7% of roasted coffee workers (37 cases) and in 4.5% of the clerks (44 cases), p < 0.01. The evaluation of IgE specific for CB gave positive results only in 3 of 10 subjects sensitized to GCB. A total of 20% of GCB workers (6 cases) complained of work-related respiratory symptoms (asthma and/or rhinitis) compared with only one subject in the roasted coffee group and one in the control group (p < 0.01). Asthma was reported by 2/31 of the green coffee workers and by 1/44 of roasted coffee workers. CONCLUSIONS: There was a significant correlation between sensitization to GCB and work related symptoms (p < 0.01), common allergic symptoms (p < 0.05) and atopy by prick test (< 0.01). These results point to the need to evaluate atopic status in workers and identify the most susceptible subjects, with the aim of informing them of their at-risk status and monitoring their progress. This makes it possible to diagnose sooner those symptoms possibly indicative of a work-related disease, because even in presence of good environmental conditions and even when symptoms are mild, it is almost always the atopic subjects who are affected.

Adult↗
PubMed1995

The nodule-specific VfENOD-GRP3 gene encoding a glycine-rich early nodulin is located on chromosome I of Vicia faba L. and is predominantly expressed in the interzone II-III of root nodules.

A nodule-specific cDNA was isolated from a Vicia faba L. nodule cDNA library. Since time course experiments revealed an early expression of this transcript in the nodule, this cDNA coded for an early nodulin and was designated VfENOD-GRP3. Based on tissue print hybridizations, we found a predominant expression of VfENOD-GRP3 transcripts in the interzone II-III region of broad bean root nodules. The encoded early nodulin ENOD-GRP3 was characterized by an N-terminal signal peptide and a C-terminal domain displaying a glycine content of 31%. Sequence analysis of a genomic VfENOD-GRP3 clone revealed that the signal peptide and the glycine-rich domain were specified by two separate exons. Primer extension experiments identified two adjacent transcription start sites for VfENOD-GRP3 transcripts. The common nodulin sequences 'AAAGAT' and 'CTCTT' were present five and three times on both DNA strands of the putative VfENOD-GRP3 promoter, respectively. Additionally, three sequence motifs resembling organ-specific elements of the soybean lbc3 gene promoter and a sequence similar to the binding site 1 for the nodule trans-acting factor Nat2 were identified. From Southern blot data and from sequence analysis of genomic PCR fragments, the presence of a VfENOD-GRP3 gene family was inferred. By PCR experiments using sequence-specific primers and DNA of microisolated chromosomes as a template, this family was located on the long arm of chromosome I.

Amino Acid Sequence↗
PubMed1999

Allergy to lentils in Mediterranean pediatric patients.

BACKGROUND: Peanuts and soybeans are the major legumes involved in human food allergy; however, scarce data exist on adverse reactions to other temperate legumes, such as lentils. OBJECTIVE: The purpose of this study was to identify patients who are allergic to lentils, to assess clinical features and other associated food allergies, and to characterize allergens in lentil extract. METHODS: Twenty-two children each with a history of adverse reactions to lentils were enrolled in the study. The diagnosis of lentil allergy was based on food challenges or a convincing history of anaphylaxis, with positive skin tests and/or specific serum IgE to lentils. Lentil components were characterized by SDS-PAGE immunoblotting. RESULTS: Twenty of 22 subjects had symptomatic allergy to lentils at the diagnostic time. The most frequent symptoms were oropharyngeal symptoms (40%) and acute urticaria (30%); 3 patients also reported symptoms when they were exposed to steam from cooked lentils. In 18 patients, symptoms after lentil ingestion started under 4 years of age (median, 2.7 years). Nine patients had allergic reactions to other legumes: chick peas (6 patients), peas (2 patients), and green beans (1 patient). Immunoblotting patterns obtained with patients' sera showed IgE-binding bands ranging from 14 to 84 kd. Five sera recognized 9 or more IgE-binding bands, and more than 50% of patients who were tested have specific IgE antibodies to 7 components in lentil extract. CONCLUSION: Allergic reactions to lentils started early in life, usually below 4 years of age; oropharyngeal symptoms and acute urticaria were the most common symptoms through ingestion, and symptomatic reactivity to chick peas is frequently associated.

Child↗
PubMed1974

Fractionation of the proteins of plant microbodies.

1. Glyoxysomes and peroxisomes have been isolated from dark- and light-grown seedlings of pumpkin (Cucurbita pepo) by sucrose-density-gradient centrifugation. 2. Pumpkin microbodies and castor-bean (Ricinus communis) glyoxysomes may be fractionated, by a combination of osmotic shock and treatment with KCl, into three distinct groups of proteins: readily soluble (matrix enzymes), solubilized in the presence of KCl (membrane-bound enzymes) and relatively insoluble (membrane ;ghost' proteins). 3. Sodium dodecyl sulphate-polyacrylamide-gel electrophoresis of ;ghost' fractions indicated that the membrane proteins were generally of low molecular weight; one gel band (mol.wt. 27000-28000) was common to all three microbodies. 4. Although there were major differences in the soluble protein components of pumpkin glyoxysomes and peroxisomes, electrophoresis of the pumpkin microbody ;ghosts' indicated that the membrane proteins were similar, four main components being common to each class of microbody (monomer molecular weights 42000, 34000, 27000 and 17000).

Centrifugation, Density Gradient↗
PubMed1995

Complementable and noncomplementable host adaptation defects in bipartite geminiviruses.

Members of the geminvirus group of plant viruses collectively infect a broad spectrum of species. Individual viruses which are genetically very similar may nevertheless have distinct host ranges. Two such geminiviruses are tomato golden mosaic virus (TGMV) and been golden mosaic virus (BGMV), for which common hosts have not previously been reported. Each virus has two genome components, designated A and B. The A component is capable of autonomous replication and encapsidation, whereas the B component provides viral functions required for the spread of infection in plants. To investigate the basis for the distinctive host ranges of BGMV and TGMV, we have introduced plasmids containing cloned viral genome components into Nicotiana benthamiana, a good host for TGMV, and bean, Phaseolus vulgaris, a good host for BGMV. We found that TGMV has a low specific infectivity for bean and is virulent, whereas BGMV has a high specific infectivity for N. benthamiana, but infections are asymptomatic and viral DNA accumulation is low. To investigate which viral functions were defective in the poor host in each case, we attempted to complement them by co-inoculation with the well-adapted virus. After inoculation of beans with both viruses, only BGMV was detected. Thus, TGMV exhibits a noncomplementable host adaptation defect in beans. This suggests that the defect has a cis-acting or virus-specific trans-acting genetic basis. In contrast, the BGMV phenotype of low DNA accumulation in N. benthamiana was partially complemented by TGMV A alone and complemented further by the complete TGMV genome. This suggests that a virus nonspecific, trans-acting factor encoded by the BGMV A component is poorly adapted to N. benthamiana. The results of this study indicate that bipartite geminivirus host range may be limited by defective virus-host interactions of more than one kind.

DNA, Viral↗
PubMed1990

Internal transcribed spacer 1 of the yeast precursor ribosomal RNA. Higher order structure and common structural motifs.

The higher order structure of the first internal transcribed spacer between the 18S and the 5.8S rRNA sequences in the Saccharomyces cerevisiae precursor ribosomal RNA has been investigated. Sites of potential base pairing in the RNA region have been determined by using a combination of enzymatic and chemical structure sensitive probes. Data generated have been used to evaluate secondary structure models predicted by minimum free energy calculations. Several alternative suboptimal structures were also evaluated. The derived model contains several stable hairpins. Theoretical secondary structural models for the corresponding RNA region from S. carlsbergensis, S. pombe, N. crassa, X. laevis, and mung bean have also been derived from identical calculations and assumptions. Certain structural motifs appear to be conserved despite extensive divergence in the base sequence. The yeast model should be a useful prototype for investigation of structure and function of precursor ribosomal RNA molecules.

Alkylating Agents↗