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PubMed1998

Occurrence of aflatoxins B1, B2, G1, and G2 in peanuts and their products marketed in the region of Campinas, Brazil in 1995 and 1996.

Samples of peanuts and their products marketed in the region of Campinas, Brazil in 1995 and 1996 were analysed in terms of aflatoxin B1, B2, G1, and G2 by thin-layer chromatography, aiming at the protection of consumer health. Of the 80 samples analysed, 35 of peanuts and 45 of peanut products, 41 (51%) presented contamination with aflatoxin, 11 of them being peanuts (27%) and 30 being products (67%), in a range of 43 to 1099 micrograms/kg for B1 + B2 + G1 + G2 with a 90th percentile of 415 (B1 + G1) and of 615 (B1 + B2 + G1 + G2). The results also demonstrated that aflatoxin B1 (AFB1) reached the highest incidence and the highest upper limits compared with all the other aflatoxins.

Aflatoxin B1↗

PubMed2002

A retrospective look at the cationic peanut peroxidase structure.

The cationic peanut peroxidase has been studied in detail, not only with regard to its peptide structure, but also to the sites and role of the three moieties linked to it. Peanut peroxidase lends itself well to a close examination as a potential example for other plant peroxidase studies. It was the first plant peroxidase for which a 3-D structure was derived from crystals, with the glycans intact. Subsequent analysis of peroxidases structures from other plants have not shown great differences to that of the peanut peroxidase. As the period of proteomics follows on the era of genomics, the study of glycans has been brought back into focus. With the potential use of peroxidase as a polymerization agent for industry, there are some aspects of the overall structure that should be kept in mind for successful use of this enzyme. A variety of techniques are now available to assay for these structures/moieties and their roles. Peanut peroxidase data are reviewed in that light, as well as defining some true terms for isozymes. Because a high return of the enzyme in a pure form has been obtained from cultured cells in suspension culture, a brief review of this is also offered.

Arachis↗

PubMed1978

Determination of aflatoxins in peanut products using reverse phase HPLC.

A high performance liquid chromatographic (HPLC) method is described for the determination of the four major aflatoxins, B1, B2, G1 and G2, in peanut products. The aflatoxins are extracted by adapting a procedure developed by Pons (1) at the SRRC, USDA, and quantitated utilizing a new 5 mum reverse-phase column with NaCl/acetontrile/methanol mobile phase (3 + 1 + 1). The 5 mum column achieved baseline resolution of each of the four aflatoxins. Retention times and peak heights were reproducible. The procedure was successfully applied to several types of peanut products and was applicable to both roasted and unroasted peanuts, which is a decided advantage over the current CB and BF extraction methods. Additionally, it can be used for sweetened peanut matrixes with no interferences in the chromatography. The total time required for sample preparation and aflatoxin determination is less than 1.5 hours.

Aflatoxins↗

PubMed2005

Enhancing resistance to Sclerotinia minor in peanut by expressing a barley oxalate oxidase gene.

Sclerotinia minor Jagger is the causal agent of Sclerotinia blight, a highly destructive disease of peanut (Arachis hypogaea). Based on evidence that oxalic acid is involved in the pathogenicity of many Sclerotinia species, our objectives were to recover transgenic peanut plants expressing an oxalic acid-degrading oxalate oxidase and to evaluate them for increased resistance to S. minor. Transformed plants were regenerated from embryogenic cultures of three Virginia peanut cultivars (Wilson, Perry, and NC-7). A colorimetric enzyme assay was used to screen for oxalate oxidase activity in leaf tissue. Candidate plants with a range of expression levels were chosen for further analysis. Integration of the transgene was confirmed by Southern-blot analysis, and gene expression was demonstrated in transformants by northern-blot analysis. A sensitive fluorescent enzyme assay was used to quantify expression levels for comparison to the colorimetric protocol. A detached leaflet assay tested whether transgene expression could limit lesion size resulting from direct application of oxalic acid. Lesion size was significantly reduced in transgenic plants compared to nontransformed controls (65%-89% reduction at high oxalic acid concentrations). A second bioassay examined lesion size after inoculation of leaflets with S. minor mycelia. Lesion size was reduced by 75% to 97% in transformed plants, providing evidence that oxalate oxidase can confer enhanced resistance to Sclerotinia blight in peanut.

Arachis↗

PubMed2006

Cytosolic triacylglycerol biosynthetic pathway in oilseeds. Molecular cloning and expression of peanut cytosolic diacylglycerol acyltransferase.

Triacylglycerols (TAGs) are the most important storage form of energy for eukaryotic cells. TAG biosynthetic activity was identified in the cytosolic fraction of developing peanut (Arachis hypogaea) cotyledons. This activity was NaF insensitive and acyl-coenzyme A (CoA) dependent. Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final step in TAG biosynthesis that acylates diacylglycerol to TAG. Soluble DGAT was identified from immature peanuts and purified by conventional column chromatographic procedures. The enzyme has a molecular mass of 41 +/- 1.0 kD. Based on the partial peptide sequence, a degenerate probe was used to obtain the full-length cDNA. The isolated gene shared less than 10% identity with the previously identified DGAT1 and 2 families, but has 13% identity with the bacterial bifunctional wax ester/DGAT. To differentiate the unrelated families, we designate the peanut gene as AhDGAT. Expression of peanut cDNA in Escherichia coli resulted in the formation of labeled TAG and wax ester from [14C]acetate. The recombinant E. coli showed high levels of DGAT activity but no wax ester synthase activity. TAGs were localized in transformed cells with Nile blue A and oil red O staining. The recombinant and native DGAT was specific for 1,2-diacylglycerol and did not utilize hexadecanol, glycerol-3-phosphate, monoacylglycerol, lysophosphatidic acid, and lysophosphatidylcholine. Oleoyl-CoA was the preferred acyl donor as compared to palmitoyl- and stearoyl-CoAs. These data suggest that the cytosol is one of the sites for TAG biosynthesis in oilseeds. The identified pathway may present opportunities of bioengineering oil-yielding plants for increased oil production.

Amino Acid Sequence↗

PubMed1968

De Novo Synthesis of Isocitritase in Peanut (Arachis hypogaea L.) Cotyledons.

Germination of peanut seed is accompanied by a rapid increase in isocitritase (isocitrate lyase, EC 4.1.3.1) during the first 4 days. The presence of cycloheximide (50 mug/ml) during water imbibition inhibited the increase in isocitritase activity. Actinomycin D conversely did not inhibit isocitritase activity until the second day of imbibition while RNA synthesis was inhibited. Germination of peanut seed in (14)C-reconstituted amino acids followed by fractionation of a 20 to 35% ammonium sulfate preparation on a Sephadex G-200 column (57-fold purification) showed that the active enzymic fraction coincided with a large peak of radioactivity. Germination of peanut seed in 45% D(2)O followed by enzyme purification and CsCl equilibrium centrifugation revealed that all the enzyme from D(2)O seed had a higher density than normal isocitritase. These data indicate that isocitritase in peanut seed is synthesized de novo.

Journal Article↗

PubMed1983

Identification and Metabolism of 1-(Malonylamino)cyclopropane-1-carboxylic Acid in Germinating Peanut Seeds.

Peanut seeds (Arachis hypogea L. Yue-you 551) contain 50 to 100 nanomoles per gram conjugated 1-aminocyclopropanecarboxylic acid (ACC). Based on paper chromatography, paper electrophoresis, and gas chromatography-mass spectrometry, it was verified that the major ACC conjugate was N-malonyl-ACC (MACC). Germinating peanut seeds converted [2-(14)C]ACC to ethylene 70 times more efficiently than N-malonyl-[2-(14)C]ACC; when ACC was administered, most of it was metabolized to MACC. Germinating peanut seeds produced ethylene and converted l-[3,4-(14)C]methionine to ethylene; this ethylene biosynthesis was inhibited by aminoethoxyvinylglycine. These data indicate that MACC occurs in peanut seeds but does not serve as the source of ethylene during germination; ethylene is, however, synthesized from methionine via ACC.

Journal Article↗

PubMed1983

Mechanism of iron uptake by peanut plants : I. Fe reduction, chelate splitting, and release of phenolics.

Iron deficiency in peanuts (Arachis hypogeae L.) caused an increase in release of caffeic acid, a higher rate of Fe(III) reduction, and increased rates of both Fe(III) chelate splitting and iron uptake.Experiments on Fe(III) reduction by phenolics (in vitro experiments) and by roots of Fe-deficient peanuts exclude the direct involvement of released phenolics in Fe(III) reduction by roots: Fe(III) reduction by phenolics had a pH optimum higher than 8.0 and was strongly dependent on the concentration and the stability of the supplied Fe(III) chelates. In contrast, Fe(III) reduction by roots of Fe-deficient peanuts had a pH optimum of about 5.0 and was less dependent on the stability of the supplied Fe(III) chelates. Furthermore, the observed release of phenolics into nutrient solution would have to be at least 200 times higher to attain the reduction rates of roots of Fe-deficient peanuts. The results of these experiments support the idea of an enzymic reduction of Fe(III) on the plasmalemma of cortical cells of roots.

Journal Article↗

PubMed2006

Gastro-duodenal digestion products of the major peanut allergen Ara h 1 retain an allergenic potential.

BACKGROUND: The process of gastro-duodenal digestion may play a role in determining the allergenic properties of food proteins. The sensitizing and allergenic potential of digestion products of highly degraded allergens, such as the major peanut allergen Ara h 1, is currently under debate. We evaluated the effect of in vitro gastro-duodenal digestion of Ara h 1 on T cell reactivity and basophil histamine release. METHODS: An in vitro model of gastro-duodenal digestion was used to investigate changes in the allergenic properties of Ara h 1 using in vitro assays monitoring T cell reactivity (proliferation, cytokine production) and histamine release of basophils from peanut allergic individuals. The digestion process was monitored using an SDS-PAGE gel. RESULTS: In vitro gastric digestion led to rapid degradation of Ara h 1 into small fragments M(r) L5600. Gastric digestion did not affect the ability of Ara h 1 to stimulate cellular proliferation. Gastro-duodenal digestion significantly reduced its ability to stimulate clonal expansion (P<0,05; Wilxocon's signed rank test). The Th-2 type cytokine polarization of T cells from peanut allergic donors (IFN-gamma/IL-13 ratio and IFN-gamma/IL-4 ratio of CFSE(low) CD4(+) T cells) remained unchanged regardless of the level of digestion. Histamine release of basophils from peanut allergic individuals was induced to the same extent by native Ara h 1 and its digestion products. CONCLUSION: Gastro-duodenal digestion fragments of Ara h 1 retain T cell stimulatory and IgE-binding and cross-linking properties of the intact protein.

Allergens↗

PubMed1997

Mapping and mutational analysis of the IgE-binding epitopes on Ara h 1, a legume vicilin protein and a major allergen in peanut hypersensitivity.

Peanut allergy is a significant health problem because of the prevelance and potential severity of the allergic reaction. Serum IgE from patients with documented peanut hypersensitivity reactions and overlapping peptides were used to identify the IgE-binding epitopes on the major peanut allergen, Ara h 1. At least twenty-three different linear IgE-binding epitopes, located throughout the length of the Ara h 1 protein, were identified. All of the epitopes were 6-10 amino acids in length, but there was no obvious sequence motif shared by all peptides. Four of the peptides appeared to be immunodominant IgE-binding epitopes in that they were recognized by serum from more than 80% of the patients tested and bound more IgE than any of the other Ara h 1 epitopes. Mutational analysis of the immunodominant epitopes revealed that single amino acid changes within these peptides had dramatic effects on IgE-binding characteristics. The identification and determination of the IgE-binding capabilities of core amino acids in epitopes on the Ara h 1 protein will make it possible to address the pathophysiologic and immunologic mechanisms regarding peanut hypersensitivity reactions specifically and food hypersensitivity in general.

Adult↗

PubMed2006

Genetic diversity in Aspergillus parasiticus population from the peanut agroecosystem in Argentina.

AIMS: The aims of this work were to identify potential sources of Aspergillus parasiticus inoculum and to evaluate the sclerotial and toxigenic profiles of this species from the peanut agroecosystem in Argentina. Likewise, the genetic diversity of A. parasiticus population was analysed using vegetative compatibility group (VCG) analysis. METHODS AND RESULTS: The A. parasiticus strains were isolated from soil, debris and peanut seeds in Córdoba Province, Argentina. A. parasiticus was recovered from the three sources analysed. Only 11 of 185 A. parasiticus isolates (5.9%) did not produce aflatoxins, while 57% produced sclerotia. Twenty-four VCG were identified from 63 isolates. The VCG diversity index for A. parasiticus, expressed as the number of groups divided by the total number of isolates, was 0.31. In general, there were significant differences among VCG in aflatoxin production. CONCLUSIONS: The presence of aflatoxigenic strains of A. parasiticus in the three substrates suggests that they may be an important source of aflatoxin in Argentina's peanut agroecosystem. The A. parasiticus population shows a low genetic diversity. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study showed data on inoculum distribution, aflatoxin and sclerotia production and genetic diversity in an A. parasiticus population isolated from the peanut agroecosystem in Argentina.

Aflatoxins↗

PubMed2025

From bottleneck to boom: Polyploidy, genetic instability and response to artificial selection resolve the peanut paradox.

This study, the second in a three-part series, shows how peanut's polyploid origin enabled rapid diversification and enhanced domestication potential. Building on the knowledge that cultivated peanut (Arachis hypogaea) originated from a narrow hybridization between Arachis duranensis and Arachis ipaënsis less than 10 000 years ago, we are confronted with a paradox: how did such a narrow origin give rise to so much diversity-two subspecies, six botanical varieties, and thousands of landraces differing in growth habit, seed size, and pod morphology? Although several diploid Arachis species were cultivated earlier, only the allotetraploid became fully domesticated and widely adopted. The global success of peanut, despite its narrow genetic origin, suggests that polyploidization itself facilitated domestication. To test this hypothesis, we investigated how the two diploid progenitors and neoallotetraploids derived from a single hybridization and polyploidization event responded under artificial selection. In a pollinator-free greenhouse, we advanced lineages of the neoallotetraploid and its diploid parents over 6 years, selecting for divergent seed weights. The neoallotetraploid showed a much stronger response to artificial selection than its diploid parents, while also spontaneously generating diverse phenotypic variation-including flower color, pod reticulation, and chlorophyll content-traits that distinguish A. hypogaea subspecies and landraces. These traits mirrored directional shifts in parental genome dosage caused by homoeologous exchange, supporting a causal connection with phenotype. These findings offer a compelling rationale for a domestication advantage in polyploid peanut, and provide a living demonstration of how a single ancestral tetraploid, despite an extreme genetic bottleneck, generates a phenotypic boom.

Arachis↗

PubMed1967

Aflatoxin-producing potential of isolates of the Aspergillus flavus-oryzae group from peanuts (Arachis hypogaea).

Seventy-eight samples of farmer stock peanuts, representing peanuts grown in nine different geographical areas during 1964, were assayed for aflatoxin and examined for associated microflora. Only two samples contained more than 50 ppb of aflatoxin. Infestation by members of the Aspergillus flavus-oryzae group varied from 35 to 100% of the kernels per area and from 1 to 100% of the kernels per sample. Aflatoxin production by individual isolates ranged from 0 to 349,143 ppb under the test conditions employed. In general, the isolates produced 8 to 10 times more B(1) than B(2), and no isolate producing aflatoxins G(1) or G(2) was found. The importance of proper postharvest handling of peanuts is emphasized by the prevalence of isolates of A. flavus-oryzae capable of producing aflatoxins on farmers stock peanuts.

Aflatoxins↗

PubMed1968

Factors influencing aflatoxin accumulation in peanut kernels and the associated mycoflora.

Accumulation of aflatoxin in Spanish peanut kernel samples from different geographical areas in Texas during 1966, as detected by the thin-layer chromatographic method, was relatively low. Analysis of samples obtained from growers using artificial drying equipment (forced air and supplemental heat), when windrow conditions were unfavorable for rapid drying, suggests that this practice reduces the possibility of aflatoxin accumulation. In general, peanuts harvested from land planted to peanuts the previous year were more highly infested with fungi and contained more aflatoxin than peanuts grown on land planted with rye, oats, melons, or potatoes the previous year. Aflatoxin incidence tended to decrease from south to north Texas. These findings verify previous research observations that moist tropical climates are conducive to fungal infestation and aflatoxin accumulation. Detection of aflatoxin in sound mature kernels (kernels screened for minimal size) indicates that the practice of screening for removal of small immature kernels and removal of obviously damaged kernels does not completely eliminate aflatoxin contamination.

Aflatoxins↗

PubMed2005

Identification of potentially cross-reactive peanut-lupine proteins by computer-assisted search for amino acid sequence homology.

BACKGROUND: Allergic cross-reactions are an issue of major concern because of implications for public health. The molecular basis of cross-allergy is the similarity of epitopes belonging to proteins of different organisms. Lupine is an emerging cause of food allergy, which has become a 'hot topic' because of recent large-scale introduction into processed foods and frequent cross-reactions with other members of the legume family. However, no lupine allergen has been characterized thus far. Prompted by a recently reported case of peanut-lupine cross-allergy, we wished to identify the possible cross-reactive allergen(s) between the two vegetal species. METHODS: We used computer-aided amino acid sequence comparison, a well-established technique for the study of protein homology, and followed the FAO/WHO guidelines for the identification of potential allergens. We also performed a three-dimensional modeling of the suspected cross-reactive proteins to compare their molecular surfaces. RESULTS: We found a highly significant sequence homology and molecular similarity between allergen Ara h 8 of peanut and pathogenesis-related protein PR-10 of white lupine. Another protein of lupine, the beta-conglutin precursor, was found to be significantly homologous to the Ara h 1 allergen of peanut. The molecular surfaces of Ara h 8 and PR-10 were remarkably similar. CONCLUSIONS: Our in silico data allow to predict the allergenicity of PR-10 and beta-conglutin precursor of white lupine according to FAO/WHO guidelines. Amino acid sequence homology also suggests that these proteins could be responsible, at least in part, for some of the allergic cross-reactions between peanut and lupine reported in the literature.

Allergens↗

PubMed1999

Molecular cloning and epitope analysis of the peanut allergen Ara h 3.

Peanut allergy is a significant IgE-mediated health problem because of the increased prevalence, potential severity, and chronicity of the reaction. Following our characterization of the two peanut allergens Ara h 1 and Ara h 2, we have isolated a cDNA clone encoding a third peanut allergen, Ara h 3. The deduced amino acid sequence of Ara h 3 shows homology to 11S seed-storage proteins. The recombinant form of this protein was expressed in a bacterial system and was recognized by serum IgE from approximately 45% of our peanut-allergic patient population. Serum IgE from these patients and overlapping, synthetic peptides were used to map the linear, IgE-binding epitopes of Ara h 3. Four epitopes, between 10 and 15 amino acids in length, were found within the primary sequence, with no obvious sequence motif shared by the peptides. One epitope is recognized by all Ara h 3-allergic patients. Mutational analysis of the epitopes revealed that single amino acid changes within these peptides could lead to a reduction or loss of IgE binding. By determining which amino acids are critical for IgE binding, it might be possible to alter the Ara h 3 cDNA to encode a protein with a reduced IgE-binding capacity. These results will enable the design of improved diagnostic and therapeutic approaches for food-hypersensitivity reactions.

Allergens↗

PubMed2006

PeanutMap: an online genome database for comparative molecular maps of peanut.

BACKGROUND: Molecular maps have been developed for many species, and are of particular importance for varietal development and comparative genomics. However, despite the existence of multiple sets of linkage maps, databases of these data are lacking for many species, including peanut. DESCRIPTION: PeanutMap http://peanutgenetics.tamu.edu/cmap provides a web-based interface for viewing specific linkage groups of a map set. PeanutMap can display and compare multiple maps of a set based upon marker or trait correspondences, which is particularly important as cultivated peanut is a disomic tetraploid. The database can also compare linkage groups among multiple map sets, allowing identification of corresponding linkage groups from results of different research projects. Data from the two published peanut genome map sets, and also from three maps sets of phenotypic traits are present in the database. Data from PeanutMap have been incorporated into the Legume Information System website http://www.comparative-legumes.org to allow peanut map data to be used for cross-species comparisons. CONCLUSION: The utility of the database is expected to increase as several SSR-based maps are being developed currently, and expanded efforts for comparative mapping of legumes are underway. Optimal use of these data will benefit from the development of tools to facilitate comparative analysis.

Arachis↗

PubMedDate not supplied

Rapid detection of Aspergillus flavus contamination in peanut with novel delayed luminescence spectra.

Employing a luminescence spectrometer the usefulness of light-induced delayed luminescence (DL) for the detection of aflatoxinB1 (AfB1) contamination in whole peanut was studied. Peanut was artificially contaminated with Aspergillus flavus (7.5 x 10(5)conidia/mL) and incubated for 0-72 h. The DL and fluorescence spectra of contaminated peanut were obtained by a luminescence spectrometer. The correlation between the spectra and contamination levels was established. The DL and fluorescence intensity has a negative correlation with the AfB1 concentration. Our results suggested that the DL technique might be useful for the rapid and noninvasive evaluation of AfB1 contamination levels in whole peanut.

Aflatoxin B1↗