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PubMed2000

The influence of storage practices on aflatoxin contamination in maize in four agroecological zones of Benin, west Africa.

Aflatoxin level in 300 farmers' stores in four agro-ecological zones in Benin, a west African coastal country, were determined over a period of 2 years. At sampling a questionnaire was used to evaluate maize storage practices. Farmers were asked what storage structure they used, their storage form, storage period, pest problems in storage and what was done against them. Beninese farmers often changed their storage structures during the storage period, transfering the maize from a drying or temporary store to a more durable one. Most of the farmers complained about insects damaging stored maize. Often, storage or cotton insecticides were utilized against these pests. Regression analysis identified those factors that were associated with increased or reduced aflatoxin.Maize samples in the southern Guinea and Sudan savannas were associated with higher aflatoxin levels and the forest/savanna mosaic was related to lower toxin levels. Factors associated with higher aflatoxin were: storage for 3-5 months, insect damage and use of Khaya senegalensis-bark or other local plants as storage protectants. Depending on the agroecological zone, storage structures that had a higher risk of aflatoxin development were the "Ago", the "Secco", the "Zingo" or storing under or on top of the roof of the house. Lower aflatoxin levels were related to the use of storage or cotton insecticides, mechanical means or smoke to protect against pests or cleaning of stores before loading them with the new harvest. Fewer aflatoxins were found when maize was stored in the "Ago" made from bamboo or when bags were used as secondary storage containers.

Journal Article↗

PubMed2003

Maize stem tissues: ferulate deposition in developing internode cell walls.

It has been hypothesized that ferulates are only deposited in the primary cell wall of grasses. To test this hypothesis, the fourth elongating, above-ground internode of maize (Zea mays l.) was sampled from three maize hybrids throughout development. Cell wall composition was determined by the Uppsala Dietary Fibre method. Ester- and ether-linked ferulates were determined by HPLC analysis of ferulic acid released from the internodes by low and high temperature alkaline treatments. Internode length increased from 9 to 152 mm over 96 days of growth, with elongation being complete in the first 12 days. More than half of the cell wall material in the maize internodes accumulated after elongation had ended. Deposition of cell wall material appeared to reach its maximum extent 40 days after sampling began, well before physiological maturity of the maize plants. Galactose and arabinose began to accumulate early in cell wall development which was presumed to be associated with primary wall growth during internode elongation. The major secondary wall constituents (analyzed as glucose, xylose, and Klason lignin) did not begin to accumulate rapidly until shortly before internode elongation ended. Ferulate ester deposition began before ferulate ethers were observed in the cell wall, but both forms of ferulate continued to accumulate in secondary cell walls, long after internode elongation had ceased. These data clearly show that contrary to the hypothesis, ferulate deposition was not restricted to the primary wall and that active lignin/polysaccharide cross-linking mediated by ferulates occurs in the secondary wall.

Cell Wall↗

PubMed1997

Maize and foxtail millet as substantial sources of dietary lead intake.

In 1996, 24-h food duplicate samples were collected from two groups of 50 non-smoking women each; one group was in Jinan, the capital city of Shandong Province in China, and the other in a farming village in the Zhangqiu area some 30 km away from the city. The people in the village took significantly more dietary lead (46 micrograms/day) than their counterparts in the city (26 micrograms/day), and blood lead concentrations (35 and 50 micrograms/l for the urban and the rural people, respectively) were in parallel with the dietary lead intake. Search for cereals as the determinants of dietary lead intake and blood lead concentration by multiple regression analysis showed that maize was the most influential source of dietary lead intake among the four common cereals of wheat, rice, foxtail millet (to be called just millet) and maize, whereas millet was the leading determinant of the blood lead level among the four cereals although the influential power was weaker than millet for dietary lead. Lead content in maize (47 ng/g) and millet (47 ng/g) was twice or even more times higher than the levels in wheat (26-30 ng/g) and rice (20-21 ng/g). The significant roles of non-rice/non-wheat cereals such as millet and maize as possible dietary lead sources for farming populations are discussed.

Adult↗

PubMed2004

Effect of elemental sulphur on solubility of soil heavy metals and their uptake by maize.

A pot experiment was conducted to study the influence of elemental sulphur (S) on solubility of soil Pb, Zn and Cd and uptake by maize (Zea mays L.). Two rates of elemental sulphur (S) applied at 0 (S0) and 200 (S200) mmol kg(-1) soil with three rates of each heavy metal at Pb, 0 (Pb0), 200 (Pb200), 400 (Pb400) mg kg(-1) soil, Zn, 0 (Zn0), 100 (Zn100), 200 (Zn200) mg kg(-1) soil and Cd, 0 (Cd0), 50 (Cd50), 100 (Cd100) mg kg(-1) soil, respectively. The result showed that with S application at 200 mmol S kg(-1), soil pH decreased about 0.3 unit and the solubility of the Zn and Cd was significantly increased, but the solubility of Pb had no significant influence. The concentration of Pb, Zn and Cd in maize shoots and roots were increased with increasing rates of heavy metals. However, the concentration of Zn and Cd in shoots and roots were higher with application of S rather than without S but no significant difference was found for Pb. The highest concentration of Zn in the shoots was 2.3 times higher with application of S rather than without at the same rate of Zn, 200 mg kg(-1). Plant biomass was also significantly affected by the application of S and of heavy metals. With heavy metal addition, the shoot and root biomass were decreased with the rates of those of heavy metals increased either with or without application of S. However, the shoot biomass was significantly decreased with S application at the same rate of heavy metals except that with Zn addition. The removal of Cd and Pb by maize uptake and accumulation with application of S had no significant increase compared to that without, but the removal Zn by maize uptake from the soil increased by application of S, 90.9 microg plant(-1) contrast to 25.7 microg plant(-1) at Zn200 within a growth period of only 40 days.

Biomass↗

PubMed2000

Fusaria and fumonisins in maize from Ghana and their co-occurrence with aflatoxins.

Fifteen maize samples from four markets and processing sites in Accra, Ghana were analysed for fumonisins B1, B2, and B3. All samples contained fumonisins. Total fumonisin levels for 14 samples ranged from 70 to 4222 microg kg(-1). One sample of visibly mouldy kernels contained 52 670 microg kg(-1) total fumonisins. Mycological examination of the samples showed Aspergillus spp. as the most dominant fungi (76.4%) followed by Penicillium spp. (19.9%). Fusarium formed 2.6% with Fusarium verticillioides as the predominant Fusarium species. Thirty-two Fusarium strains representing five species isolated from the maize samples were tested for the production of fumonisins in maize substrates. From 95% (21 of 22) of the F. verticillioides strains tested, all three types of fumonisins were produced. Total fumonisin levels ranged from 127 to 11 052 microg g(-1). Additional studies on maize samples from 15 processing sites in Accra revealed a co-occurrence of both fumonisins and aflatoxins in 53% (8 of 15) of the samples.

Aflatoxins↗

PubMed2000

Impact of environment and interspecific interactions between spoilage fungi and Aspergillus ochraceus on growth and ochratoxin production in maize grain.

Using layers of irradiated but still fertile maize grain, the effects of water activity (0.995, 0.95 a(w)) and temperature (18, 30 degrees C) on interspecific interactions between Aspergillus ochraceus and five other spoilage fungi were examined. Asp. ochraceus was not competitive against Asp. flavus, Asp. niger, or Alternaria alternata at 18 degrees C when water was freely available (0.995 a(w)), while at 0.95 a(w) it was dominant against Asp. candidus, Asp. flavus and Alt. alternata. At 30 degrees C and 0.995 a(w), Asp. ochraceus was dominated by other fungi, except Alt. alternata, and was mutually antagonistic to Asp. candidus and Eurotium amstelodami. However, at 30 degreees C and 0.95 a(w), it was competitive against Asp. candidus and Alt. alternata, but not against the other species examined. The overall Index of Dominance showed that Asp. ochraceus was not competitive under the conditions examined here. At 18 degrees C ochratoxin production by Asp. ochraceus was inhibited significantly by Asp. candidus (0.995 and 0.95 a(w)) and Asp. niger (0.995 a(w)). When grown on maize grain at 30 degrees C, ochratoxin production by Asp. ochraceus was significantly inhibited by other spoilage fungi when both were grown on maize grain, especially by Asp. niger and E. amstelodami (0.995 a(w)) and Asp. flavus at 0.95 a(w). These results suggest that, to a large extent, A. ochraceus is not as competitive as some other spoilage fungi in primary resource capture on maize grain at a(w) of 0.95 or above, although it may modify resource quality and influence secondary colonisation by other species under the conditions tested.

Alternaria↗

PubMed2001

Glutathione reductase activity and chilling tolerance are induced by a hydroxylamine derivative BRX-156 in maize and soybean.

The possible contribution of antioxidants in the improvement of stress tolerance induced by the hydroxylamine derivative BRX-156 was studied in two thermophilic crops, soybean (Glycine max (L.) Merr.) and maize (Zea mays L.) both during germination and at the seedling stage. The most effective concentration of BRX-156 for an increase in stress tolerance was determined by the complex stressing vigour test (CSVT), in which seeds were germinated under simultaneous anoxia and chilling (5 degrees C) stresses. Under CSVT conditions the activity of glutathione reductase (GR, EC 1.6.4.2), was increased by BRX-156 by up to 200 and 150% in soybean and maize, respectively. Treatment with BRX-156 only resulted in a significantly greater activity of glutathione S-transferase (GST, EC 2.5.1.18) in maize. When young seedlings were chilled at 5 degrees C for a week, the increase in recovery induced by BRX-156 was accompanied by increased GR activity. The GSH synthesis was not affected by BRX-156 under these conditions. Induction of GR activity contributes to the improvement of abiotic stress tolerance by BRX-156 in maize and soybean.

Journal Article↗

PubMed2003

Changes of copper speciation in maize rhizosphere soil.

Chemical forms of copper in the rhizosphere and bulk soil of maize were investigated using rhizobox cultivation and sequential extraction techniques. The copper accumulations were also determined. The results demonstrated that there were continuous changes in copper fractionation within the maize rhizosphere. Initially, the amount of exchangeable copper increased before dropping below the initial level after 40 days or so. Carbonate associated copper followed a similar trend of change, but with a slower pace than the exchangeable copper. The increase in carbonate associated copper only become evident after 30 days, with the net loss occurring after 60 days. There were also initial increases in oxide bound copper as well as decreases in the organic matter associated copper, both followed by a turnover after 40-50 days. The accumulation of copper in the maize plant was found to be biomass dependent. The amount of accumulated copper absorbed in the plant material exceeded the initial quantity of the exchangeable copper in the soil, revealing a transformation from less bioavailable to more bioavailable fractions. During cultivation, decreases in redox potential and increases in pH, dissolved organic carbon (DOC), and microbial activity in the maize rhizosphere were observed. The change in copper speciation may result from root-induced changes in DOC, redox potential, and microbial activity in the rhizosphere.

Agriculture↗

PubMed2000

Genomic cloning and characterization of mitochondrial elongation factor Tu (EF-Tu) gene (tufM) from maize (Zea mays L.).

We have cloned and characterized a mitochondrial elongation factor Tu (EF-Tu) gene (tufM) in maize (Zea mays L.). This maize tufM gene encoded a polypeptide of 452 amino acid residues, consisting of a putative transit peptide of 55 residues and a mature EF-Tu of 397 residues. The coding region was composed of 12 exons and 11 introns that ranged from 76 to 1673bp in length. The deduced amino acid sequence showed 85.9% and 61.2% identity with Arabidopsis mitochondrial EF-Tu and Arabidopsis chloroplast EF-Tu sequence respectively. The transcription initiation site was determined to be 165bp upstream of the AUG initiation codon by primer extension analysis. Southern blot analysis revealed that the cloned EF-Tu gene was encoded by the members of small gene family in maize. Although this gene does not resemble the Arabidopsis nuclear tufA gene, which encodes the plastid EF-Tu, and does not contain sequence elements found in all cyanobacterial and plastid tufA genes, the predicted amino acid sequence includes an N-terminal extension that resembles a mitochondrial targeting sequence, and shares three unique sequence elements with mitochondrial EF-Tu's from Arabidopsis thaliana, Saccharomyces cerevisiae, and Homo sapiens. Therefore, we concluded that this gene encodes the maize mitochondrial EF-Tu.

Amino Acid Sequence↗

PubMed1991

Nucleic acids in mummified plant seeds: biochemistry and molecular genetics of pre-Columbian maize.

Nucleic acids fractions were isolated from pre-Columbian maize seeds and characterized using different approaches such as polyacrylamide gel electrophoresis, anti-DNA antibody binding, HPLC fractionation, molecular hybridization with cloned genes, and DNA amplification by the polymerase chain reaction. The nucleic acids were found to be very depolymerized (less than or equal to 140 base pairs in length) and composed mainly of ribosomal RNA. Despite the very low amount and degree of polymerization of seed DNA, specific maize nuclear Mu1, Mu4, Mu8 and, possibly, Mu5 element components could be detected, thanks to the use of amplification systems as short as 90 bp. The results suggest that evaluation of the relative proportions of Mu-type element components and, possibly, other maize genomic components in single mummified kernels, may offer a new key to the study of ancient maize populations.

Base Sequence↗

PubMed2004

Quantitation of transgenic Bt event-176 maize using double quantitative competitive polymerase chain reaction and capillary gel electrophoresis laser-induced fluorescence.

In this work, a new procedure useful to quantitatively analyze genetically modified organisms (GMOs) in foods is described and applied to analyze transgenic Bt Event-176 maize. The method developed consists of coamplifications of specific DNA maize sequences with internal standards using quantitative competitive PCR (QC-PCR). The QC-PCR products are quantitatively analyzed using a capillary gel electrophoresis (CGE) with laser-induced fluorescence detection (LIF) method developed at our laboratory that utilizes a physically adsorbed coating. The CGE-LIF procedure allows the use of internal standards differing by only 10 bp from the original target fragments, to our knowledge, the smallest size difference that can be found in the bibliography for QC-PCR of GMOs. A spectrofluorometric procedure using ROX reference dye is proposed to solve calibration problems of input DNA concentration. It is demonstrated that the use of ROX drastically enhances the accuracy of the quantitative analysis by QC-PCR. Reproducibility of analysis times and corrected peak areas (measured as target/competitor PCR products ratio) for the CGE-LIF separations are determined to be better than 0.91 and 1.93% (RSD, n = 15) respectively, for three different days. It is shown that CGE-LIF provides better resolution and a signal/noise ratio improvement of approximately 700-fold compared to slab gel electrophoresis. The good possibilities in terms of quantitative analysis of GMOs provided by this new method are confirmed by determining the Bt Event-176 maize content in certified reference maize powder and food samples of known composition. This procedure opens the possibility for accurate quantitation of multiple GMOs in a single run.

Bacterial Proteins↗

PubMed1991

Characterization of maize microtubule-associated proteins, one of which is immunologically related to tau.

Microtubule-associated proteins (MAPs) are identified as proteins that copurify with tubulin, promote tubulin assembly, and bind to microtubules in vitro. Higher plant MAPs remain mostly unknown. One example of non-tubulin carrot proteins, which bind to neural microtubules and induce bundling, has been reported so far [Cyr, R. J., & Palewitz, B. A. (1989) Planta 177, 245-260]. Using taxol, we developed an assay where higher plant microtubules were induced to self-assemble in cytosolic extracts of maize cultured cells and were used as the native matrix to isolate putative plant MAPs. Several polypeptides with an apparent molecular masses between 170 and 32 kDa copolymerized with maize microtubules. These putative maize MAPs also coassembled with pig brain tubulin through two cycles of temperature-dependent assembly-disassembly. They were able to initiate and promote MAP-free tubulin assembly under conditions of nonefficient self-assembly and induced bundling of both plant and neural microtubules. One of these proteins, of about 83 kDa, cross-reacted with affinity-purified antibodies against rat brain tau proteins, suggesting the presence of common epitope(s) between neural tau and maize proteins. This homology might concern the tubulin-binding domain, as plant and neural tubulins are highly conserved and the plant polypeptides coassembled with brain tubulin.

Animals↗

PubMed2000

RPD3-type histone deacetylases in maize embryos.

Posttranslational core histone acetylation is established and maintained by histone acetyltransferases and deacetylases. Both have been identified as important transcriptional regulators in various eukaryotic systems. In contrast to nonplant systems where only RPD3-related histone deacetylases (HD) have been characterized so far, maize embryos contain three unrelated families of deacetylases (HD1A, HD1B, and HD2). Purification, cDNA cloning, and immunological studies identified the two maize histone deacetylase HD1B forms as close homologues of the RPD3-type deacetylase HDAC1. Unlike the other maize deacetylases, HD1A and nucleolar HD2, HD1B copurified as a complex with a protein related to the retinoblastoma-associated protein, Rbap46. Two HD1B mRNA species could be detected on RNA blots, encoding proteins of 58 kDa (HD1B-I) and 51 kDa (HD1B-II). HD1B-I (zmRpd3) represents the major enzyme form as judged from RNA and immunoblots. Levels of expression of HD1B-I and -II mRNA differ during early embryo germination; HD1B-I mRNA and protein are present during the entire germination pathway, even in the quiescent embryo, whereas HD1B-II expression starts when meristematic cells enter S-phase of the cell cycle. In line with previous results, HD1B exists as soluble and chromatin-bound enzyme forms. In vivo treatment of meristematic tissue with the deacetylase inhibitor HC toxin does not affect the expression of the three maize histone deacetylases, whereas it causes downregulation of histone acetyltransferase B.

Amino Acid Sequence↗

PubMed2003

Enhanced resistance to Helicoverpa zea in tobacco expressing an activated form of maize ribosome- inactivating protein.

Progeny of two transgenic tobacco (Nicotiana tabacum L.) lines that expressed an activated form of maize (Zea mays L.) ribosome-inactivating protein (RIP) had varying resistance to the insect species tested. A subset of R(2) plants from the two lines appeared to be more resistant to larvae of the cigarette beetle, Lasioderma serricorne (F.), and the tobacco hornworm, Manduca sexta (L.) than the wild type plants. Progeny (R(3)) of the more resistant R(2) plants were tested more extensively for insect resistance. Resistance to the corn earworm, Helicoverpa zea (Boddie), was most consistent, with significantly decreased feeding often accompanied by increased mortality and reduced weights of survivors fed on leaf disks of the two transgenic lines compared to the wild type. The amount of damage by H. zea was significantly inversely correlated with levels of RIP. Resistance of RIP-producing plants to H. zea was greater than expected on the basis of prior in vitro results using diet-incorporated maize RIP. The R(3) transgenic plant leaf disks were also often more resistant to feeding by larvae of L. serricorne compared to wild type plants. Although reduced feeding by M. sexta was noted when they were fed leaf disks from transgenic compared to wild type plants the first day of exposure, differences were not significant. This information provides further support for maize RIP having a role in resistance to maize-feeding insects.

Animals↗

PubMed2003

Reliable detection and identification of genetically modified maize, soybean, and canola by multiplex PCR analysis.

Multiplex PCR procedures were developed for simultaneously detecting multiple target sequences in genetically modified (GM) soybean (Roundup Ready), maize (event 176, Bt11, Mon810, T14/25), and canola (GT73, HCN92/28, MS8/RF3, Oxy 235). Internal control targets (invertase gene in corn, lectin and beta-actin genes in soybean, and cruciferin gene in canola) were included as appropriate to assess the efficiency of all reactions, thereby eliminating any false negatives. Primer combinations that allowed the identification of specific lines were used. In one system of identification, simultaneous amplification profiling (SAP), rather than target specific detection, was used for the identification of four GM maize lines. SAP is simple and has the potential to identify both approved and nonapproved GM lines. The template concentration was identified as a critical factor affecting efficient multiplex PCRs. In canola, 75 ng of DNA template was more effective than 50 ng of DNA for the simultaneous amplification of all targets in a reaction volume of 25 microL. Reliable identification of GM canola was achieved at a DNA concentration of 3 ng/microL, and at 0.1% for GM soybean, indicating high levels of sensitivity. Nonspecific amplification was utilized in this study as a tool for specific and reliable identification of one line of GM maize. The primer cry1A 4-3' (antisense primer) recognizes two sites on the DNA template extracted from GM transgenic maize containing event 176 (European corn borer resistant), resulting in the amplification of products of 152 bp (expected) and 485 bp (unexpected). The latter fragment was sequenced and confirmed to be Cry1A specific. The systems described herein represent simple, accurate, and sensitive GMO detection methods in which only one reaction is necessary to detect multiple GM target sequences that can be reliably used for the identification of specific lines of GMOs.

Brassica napus↗

PubMed2004

Sequential in vitro pepsin digestion of uncooked and cooked sorghum and maize samples.

An in vitro protein digestion study, using pepsin, was carried out in uncooked and cooked sorghum and maize flour samples. The digestibility values from the uncooked samples showed that sorghum presents digestibility values similar to those of maize. In the case of the cooked samples, it was found that a wet cooking procedure promotes a decrease in sorghum protein digestibility when compared to maize. Electrophoresis was used to follow the in vitro pepsin sequential digestion procedure, and infrared spectroscopy was applied to establish its efficiency. SDS-PAGE results showed that both uncooked samples (sorghum and maize) behave in a similar way. The wet cooking procedure increases the amount of high molecular weight aggregates and promotes the appearance of two nonreducible and nondigestible 45 and 47 kDa proteins. These two protein fractions are directly related to the loss of digestibility. It was also shown that in cooked sorghum the monomers (gamma-, alpha-, and beta-) are more resistant to digestion than the corresponding uncooked samples.

Digestion↗

PubMed2004

Safety assessment by in vitro digestibility and allergenicity of genetically modified maize with an amaranth 11S globulin.

Prospective testing for allergenicity of proteins obtained from sources with no prior history of causing allergy has been difficult to perform. Thus, the objective of this work was to assess the food safety of genetically modified maize with an amaranth globulin protein termed amarantin. Transgenic maize lines evaluated showed, in relation to nontransgenic, 4-35% more protein and 0-44% higher contents of specific essential amino acids. Individual sequence analysis with known amino acid sequences, reported as allergens, showed that none of these IgE elicitors were identified in amarantin. Amarantin was digested within the first 15 min by Simulated Gastric Fluid treatment as observed by Western blot. Expressed amarantin did not induce important levels of specific IgE antibodies in BALB/c mice, as analyzed by ELISA. We conclude that the transgenic maize with amarantin is not an important allergenicity inducer, just as nontransgenic maize.

Allergens↗

PubMed2005

Development of a multiplex polymerase chain reaction method for simultaneous detection of eight events of genetically modified maize.

In this study, we developed a novel multiplex polymerase chain reaction (PCR) method for simultaneous detection of up to eight events of genetically modified (GM) maize within a single reaction. The eight detection primer pairs designed to be construct specific for eight respective GM events (i.e., Bt11, Event176, GA21, MON810, MON863, NK603, T25, and TC1507) and a primer pair for an endogenous reference gene, ssIIb, were included in the nonaplex(9plex) PCR system, and its amplified products could be distinguished by agarose gel and capillary electrophoreses based on their different lengths. The optimal condition enabled us to reliably amplify two fragments corresponding to a construct specific sequence and a taxon specific ssIIb in each of the eight events of GM maize and all of nine fragments in a simulated GM mixture containing as little as 0.25% (w/w) each of eight events of GM maize. These results indicate that this multiplex PCR method could be an effective qualitative detection method for screening GM maize.

Base Sequence↗