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PubMed2006

Qualitative and quantitative polymerase chain reaction analysis for genetically modified maize MON863.

Qualitative and quantitative analytical methods were developed for the new event of genetically modified (GM) maize, MON863. One specific primer pair was designed for the qualitative polymerase chain reaction (PCR) method. The specificity and sensitivity of the designed primers were confirmed. PCR was performed on genomic DNAs extracted from MON863, other GM events, and cereal crops. Single PCR product was obtained from MON863 by the designed primer pair. Eight test samples including GM maize MON863 were prepared at 0.01 approximately 10% levels and analyzed by PCR. Limit of detection of the method was 0.01% for GM maize MON863. On the other hand, another specific primer pair and probe were also designed for quantitative method using a real-time polymerase chain reaction. As a reference molecule, a plasmid was constructed from a taxon-specific DNA sequence for maize, a universal sequence for a cauliflower mosaic virus (CaMV) 35S promoter used in most genetically modified organisms, and a construct-specific DNA sequence for the MON863 event. Six test samples of 0.1, 0.5, 1.0, 3.0, 5.0 and 10.0% of GM maize MON863 were quantitated for the validation of this method. At the 3.0% level, the bias (mean vs true value) for MON863 was 3.0%, and its relative standard deviation was 5.5%. Limit of quantitation of the method was 0.5%. These results show that the developed PCR methods can be used to qualitatively and quantitatively detect GM maize MON863.

DNA Primers↗

PubMed2006

Analysis of European and north american maize inbred and hybrid lines by monolithic and perfusion reversed-phase high-performance chromatography and multivariate analysis.

Monolithic and perfusion RP-HPLC methods have been employed for the separation of maize proteins from several European and North American inbred and hybrid lines in analysis times close to 4 min for the perfusion column and close to 8 min for the monolithic column. A study of the repeatability of the protein extraction conditions and of the perfusion and monolithic RP-HPLC methods was performed, indicating low values of variance for the relative peak areas and for the retention times. On the other hand, a low inter-kernel variability of these chromatographic parameters was also found, confirming the possibility of a variety identification and classification of maize inbred and hybrid lines by using a RP-HPLC analysis of the maize proteins. A multivariate analysis of the chromatographic data was carried out in order to characterize and identify the inbred and hybrid maize lines. Cluster analysis of the data showed how far or closely related were the maize lines. Principal component analysis showed that protein chromatographic data had enough information to distinguish between the different groups of maize lines. Finally, a linear discriminant analysis enabled the correct classification of the inbred and hybrid lines according to their geographical origin showing the best percentage of cases correctly classified for monolithic RP-HPLC.

Chromatography, High Pressure Liquid↗

PubMed2000

Identification and effects of maize silk volatiles on cultures of Aspergillus flavus.

Volatiles generated from corn silks of individual genotypes of maize were found to exhibit differences in biological activities when the volatiles were exposed to 5-day solid cultures of Aspergillus flavus. In inverted potato dextrose-agar Petri plate bioassays, it was found that volatiles emitted from silks of the different maize genotypes had a profound effect on the growth of the fungus and, consequently, aflatoxin production. To determine the underlying cause for this bioactivity, volatiles emitted from the maize silks were trapped on Tenax glass columns and were analyzed by GC-MS. Aflatoxin field-resistant maize genotypes exhibited a larger relative concentration of the antifungal aldehyde, furfural (2-furancarboxaldehyde), when compared to the relative concentrations of the field-susceptible varieties tested. In a closed-container 5-day study, it was observed that fresh 1- and 4-day-old corn silk samples of aflatoxin-resistant maize genotypes emitted higher concentrations of furfural compared to those from susceptible genotypes. This observation probably explains the reason for the bioactivity observed in the in vitro bioassays, and the presence of furfural appears to contribute to a defense mechanism for protecting the developing maize kernel from fungal attack.

Aflatoxins↗

PubMed1998

Excision of Ds1 from the genome of maize streak virus in response to different transposase-encoding genes.

We have previously established a reverse genetic system for studying excision of the transposable element Ds1 in maize plants. Ds1 carried by the genome of maize streak virus (MSV) is introduced into maize plants by agroinfection. Excision of Ds1 from the MSV genome depends on the presence of an active Ac element in the recipient maize plants. With the purpose of exploiting MSV-Ds1 as vector for maize transformation, we studied different genes encoding the transposase (TPase) for their efficiency of activating Ds1 excision. These genes were inserted in the same T-DNA carrying MSV-Ds1 and introduced into maize plants by Agrobacterium-mediated transformation. We showed that the wild-type TPase transcribed by the 2' promoter produced much higher efficiency of Ds1 excision than that transcribed by the Ac promoter. In contrast to what had been observed in tobacco and petunia, the truncated TPase (103-807) lacking the amino-terminal 102 amino acids gave a much more reduced Ds1 excision efficiency than the wild-type TPase when both genes were transcribed by the 2' promoter.

DNA Transposable Elements↗

PubMed2000

The promoter of rbcS in a C3 plant (rice) directs organ-specific, light-dependent expression in a C4 plant (maize), but does not confer bundle sheath cell-specific expression.

The small subunit of ribulose-bisphosphate carboxylase (Rubisco), encoded by rbcS, is essential for photosynthesis in both C3 and C4 plants, even though the cell specificity of rbcS expression is different between C3 and C4 plants. The C3 rbcS is specifically expressed in mesophyll cells, while the C4 rbcS is expressed in bundle sheath cells, and not mesophyll cells. Two chimeric genes were constructed consisting of the structural gene encoding beta-glucuronidase (GUS) controlled by the two promoters from maize (C4) and rice (C3) rbcS genes. These constructs were introduced into a C4 plant, maize. Both chimeric genes were specifically expressed in photosynthetic organs, such as leaf blade, but not in non-photosynthetic organs. The expressions of the genes were also regulated by light. However, the rice promoter drove the GUS activity mainly in mesophyll cells and relatively low in bundle sheath cells, while the maize rbcS promoter induced the activity specifically in bundle sheath cells. These results suggest that the rice promoter contains some cis-acting elements responding in an organ-specific and light-inducible regulation manner in maize but does not contain element(s) for bundle sheath cell-specific expression, while the maize promoter does contain such element(s). Based on this result, we discuss the similarities and differences between the rice (C3) and maize (C4) rbcS promoter in terms of the evolution of the C4 photosynthetic gene.

Base Sequence↗

PubMed2002

Differential attractiveness of induced odors emitted by eight maize varieties for the parasitoid cotesia marginiventris: is quality or quantity important?

Herbivore-induced plant volatiles can function as indirect defense signals that attract natural enemies of herbivores. Several parasitoids are known to exploit these plant-provided cues to locate their hosts. One such parasitoid is the generalist Cotesia marginiventris, which is, among others, attracted to maize volatiles induced by caterpillar damage. Maize plants can be induced to produce the same blend of attractive volatiles by treating them with regurgitant of Spodoptera species. We collected and analyzed the regurgitant-induced emissions of two plant species (cowpea and maize) and of eight Mexican maize varieties and found significant differences among their volatile emissions, both in terms of total quantity and the quality of the blends. In a Y-tube olfactometer. the odors of the same artificially induced plant species and Mexican varieties were offered in dual choice experiments to naive mated females of C. marginiventris. Wasps preferred cowpea over maize odor and, in 3 of 12 combinations with the maize varieties, they showed a preference for the odors of one of the varieties, A comparison of the odor collection with results from the behavioral assays indicates that not only the quantity of the volatile emissions, but also the quality (composition) of the volatile blends is important for attraction of C. marginiventris. The results are discussed in the context of the possibility of breeding crop varieties that are particularly attractive to parasitoids.

Animals↗

PubMed2002

Auxin stimulates S6 ribosomal protein phosphorylation in maize thereby affecting protein synthesis regulation.

Auxin is known to stimulate protein synthesis in many plant tissues, but the mechanisms involved in this process are unknown. The present research inquires whether auxin might regulate selective translation of mRNAs by inducing S6 ribosomal protein phosphorylation on the 40S ribosomal subunit in maize (Zea mays L.). Maize embryonic axes auxin-stimulated by natural (IAA) or synthetic (Dicamba or 1-NAA) auxins, selectively increased ribosomal protein synthesis. This effect was not reproduced by auxin inactive analogue 2-NAA. Enhanced S6 ribosomal protein phosphorylation on the 40S ribosomal subunit was also observed after auxin stimulation, as measured by [32P] incorporation into this protein. This increment did not occur when stimulation was performed with the inactive auxin analogue. Further, increased recruitment into polysomes of two 5'TOP-like mRNAs, encoding for the initiation translation factor eIF-iso4E and the S6 ribosomal protein, was also found after auxin stimulation of maize axes. A positive correlation was established between the levels of S6 ribosomal protein phosphorylation and the S6 ribosomal protein transcript recruitment into polysomes by means of okadaic acid or heat shock application to maize axes. These data indicate that auxin stimulates S6 ribosomal protein phosphorylation on maize ribosomes, concomitant to the recruitment of specific mRNAs (5'TOP-like mRNAs) into polysomes for translation. It is proposed that by this mechanism auxin regulate the synthesis of specific proteins in maize tissues.

Journal Article↗

PubMed2004

Ban on triazine herbicides likely to reduce but not negate relative benefits of GMHT maize cropping.

The UK Farm-Scale Evaluations (FSE) compared the effects on biodiversity of management of genetically modified herbicide-tolerant (GMHT) spring-sown crops with conventional crop management. The FSE reported larger weed abundance under GMHT management for fodder maize, one of three crops studied. Increased seed production may be important for the long-term persistence of these arable weeds and may benefit invertebrates, small mammals and seed-eating birds. In three-quarters of FSE maize fields, growers used atrazine on the conventionally managed half, reflecting contemporary commercial practice. Withdrawal of the triazine herbicides atrazine, simazine and cyanazine from approved lists of EU chemicals could therefore reduce or even reverse the reported benefits of GMHT maize. Here we analyse effects of applications of triazine herbicides in conventional maize regimes on key indicators, using FSE data. Weed abundances were decreased greatly relative to all other regimes whenever atrazine was applied before weeds emerged. Here, we forecast weed abundances in post-triazine herbicide regimes. We predict weed abundances under future conventional herbicide management to be considerably larger than that for atrazine used before weeds emerged, but still smaller than for the four FSE sites analysed that used only non-triazine herbicides. Our overall conclusion is that the comparative benefits for arable biodiversity of GMHT maize cropping would be reduced, but not eliminated, by the withdrawal of triazines from conventional maize cropping.

Atrazine↗

PubMed2005

Recruitment of entomopathogenic nematodes by insect-damaged maize roots.

Plants under attack by arthropod herbivores often emit volatile compounds from their leaves that attract natural enemies of the herbivores. Here we report the first identification of an insect-induced belowground plant signal, (E)-beta-caryophyllene, which strongly attracts an entomopathogenic nematode. Maize roots release this sesquiterpene in response to feeding by larvae of the beetle Diabrotica virgifera virgifera, a maize pest that is currently invading Europe. Most North American maize lines do not release (E)-beta-caryophyllene, whereas European lines and the wild maize ancestor, teosinte, readily do so in response to D. v. virgifera attack. This difference was consistent with striking differences in the attractiveness of representative lines in the laboratory. Field experiments showed a fivefold higher nematode infection rate of D. v. virgifera larvae on a maize variety that produces the signal than on a variety that does not, whereas spiking the soil near the latter variety with authentic (E)-beta-caryophyllene decreased the emergence of adult D. v. virgifera to less than half. North American maize lines must have lost the signal during the breeding process. Development of new varieties that release the attractant in adequate amounts should help enhance the efficacy of nematodes as biological control agents against root pests like D. v. virgifera.

Animals↗

PubMed2005

The origin of the naked grains of maize.

The most critical step in maize (Zea mays ssp. mays) domestication was the liberation of the kernel from the hardened, protective casing that envelops the kernel in the maize progenitor, teosinte. This evolutionary step exposed the kernel on the surface of the ear, such that it could readily be used by humans as a food source. Here we show that this key event in maize domestication is controlled by a single gene (teosinte glume architecture or tga1), belonging to the SBP-domain family of transcriptional regulators. The factor controlling the phenotypic difference between maize and teosinte maps to a 1-kilobase region, within which maize and teosinte show only seven fixed differences in their DNA sequences. One of these differences encodes a non-conservative amino acid substitution and may affect protein function, and the other six differences potentially affect gene regulation. Molecular evolution analyses show that this region was the target of selection during maize domestication. Our results demonstrate that modest genetic changes in single genes can induce dramatic changes in phenotype during domestication and evolution.

Agriculture↗

PubMed1986

Substrate specificity and regulation of the maize (Zea mays) leaf ADP: protein phosphotransferase catalysing phosphorylation/inactivation of pyruvate, orthophosphate dikinase.

The protein substrate specificity of the maize (Zea mays) leaf ADP: protein phosphotransferase (regulatory protein, RP) was studied in terms of its relative ability to inactivate/phosphorylate pyruvate, orthophosphate dikinase from Zea mays and the non-sulphur purple photosynthetic bacterium Rhodospirillum rubrum. The dimeric bacterial dikinase was inactivated by the maize leaf RP via phosphorylation, with a stoichiometry of approximately 1 mol of phosphate incorporated/mol of 92.7-kDa protomer. Inactivation required both ADP and ATP, with ADP being the specific donor for regulatory phosphorylation. The requirements for inactivation/phosphorylation in this heterologous system were identical with those previously established for the tetrameric maize leaf dikinase. The ADP-dependent maize leaf RP did not phosphorylate alternative protein substrates such as casein or phosvitin, and its activity was not affected by cyclic nucleotides, Ca2+ or calmodulin. The regulation of the maize leaf ADP: protein phosphotransferase was studied in terms of changes in adenylate energy charge and pyruvate concentration. The change in adenylate energy charge necessary to substantially inhibit phosphorylation of maize leaf dikinase was not suggestive of it being a physiological modulator of phosphotransferase activity. Pyruvate was a potent competitive inhibitor of regulatory phosphorylation (Ki = 80 microM), consistent with its interaction with the catalytic phosphorylated intermediate of dikinase, the true protein substrate for ADP-dependent phosphorylation/inactivation.

Adenosine Diphosphate↗

PubMed1995

Different properties of the mitochondrial and cytosolic hexokinases in maize roots.

After tissue homogenization, 43% of the total hexokinase activity found in maize radicles was recovered in the mitochondrial fraction and 35% was soluble, in the cytosol. The maize submitochondrial particles obtained after mitochondrial sonication retained a high hexokinase activity. The mitochondrial respiration (state 4 rate) was activated by glucose. This activation was blocked by carboxyatractyloside (0.5 mM) and by oligomycin (2 micrograms/ml). The affinities for ATP and glucose of both soluble and membrane-bound maize hexokinases are similar to those of yeast hexokinase. The Km for ATP of these different forms of hexokinase varied between 0.15 and 0.37 mM, and the Km for glucose between 0.05 and 0.13 mM. A major difference between the two maize hexokinase forms is that only the mitochondrial enzyme was strongly inhibited by ADP (Ki 0.04 mM). The soluble forms of hexokinase found both in the cytosol of maize radicles and in yeast are not inhibited by ADP. In a previous report [de Meis, Grieco and Galina (1992) FEBS Lett. 308, 197-201] it was shown that the mitochondrial F1-F0-ATPase can use glucose 6-phosphate and yeast hexokinase as an ATP regenerating system. We now show that the membrane-bound hexokinase and glucose 6-phosphate can also serve as an ATP regenerating system for the mitochondria of maize radicles provided that the ADP concentration is kept below 0.05 mM. Higher ADP concentrations inhibit the reverse reaction of the mitochondrial hexokinase.

Adenosine Diphosphate↗

PubMed2003

Volatile compounds produced by Lactobacillus fermentum, Saccharomyces cerevisiae and Candida krusei in single starter culture fermentations of Ghanaian maize dough.

AIMS: To identify and compare the volatile compounds associated with maize dough samples prepared by spontaneous fermentation and by the use of added starter cultures in Ghana. METHODS AND RESULTS: The starter cultures examined were Lactobacillus fermentum, Saccharomyces cerevisiae and Candida krusei. For identification of aroma volatiles, extracts by the Likens-Nickerson simultaneous distillation and extraction technique were analysed by gas chromatography-mass spectrometry (GC-MS) and using a trained panel of four judges by GC-Olfactometry (GC-sniffing). Compounds identified by GC-MS in maize dough samples after 72 h of fermentation included 20 alcohols, 22 carbonyls, 11 esters, seven acids, a furan and three phenolic compounds. Of the total 64 volatile compounds, 51 were detected by GC-sniffing as contributing to the aroma of the different fermented dough samples. Spontaneously fermented maize dough was characterized by higher levels of carbonyl compounds while fermentations with added L. fermentum recorded the highest concentration of acetic acid. S. cerevisiae produced higher amounts of fusel alcohols and increasing levels of esters with fermentation time and C. krusei showed similarity to L. fermentum with lower levels of most volatiles identified. CONCLUSION: The present study has given a detailed picture of the aroma compounds in fermented maize and demonstrated that the predominant micro-organisms in fermented maize dough can be used as starter cultures to modify the aroma of fermented maize dough. SIGNIFICANCE AND IMPACT OF THE STUDY: The study has documented the advantage of using starter cultures in African traditional food processing and provided a scientific background for introducing better controlled fermentations.

Alcohols↗

PubMed1993

Four members of the maize beta-tubulin gene family are expressed in the male gametophyte.

Four different beta-tubulin cDNA clones have been identified in maize pollen cDNA libraries. Three of the four cDNA clones represent new maize beta-tubulin genes that have been designated tub3, tub4 and tub5. It is shown that the beta-tubulin gene family in maize is more complex than originally anticipated and more complex than those in vertebrates. In the maize beta-tubulin gene family the tub3, tub4 and tub5 genes are shown to represent small beta-tubulin gene subfamilies. Differences in the abundance of the tub3, tub4 and tub5 transcripts are seen among vegetative and reproductive tissues. The tub3 and tub4 transcripts are most abundant in pollen. In spikelet development, abundance of the tub3 transcript increases markedly from the 0.7 cm to the 1.0 cm spikelets whilst the levels of tub4 transcript closely resemble those of total beta-tubulin transcript in the organs examined. The tub3 and tub4 genes appear to have diverged recently in the evolution of the maize beta-tubulin gene family. The tub5 gene is expressed in pollen but its transcript is most abundant in maize vegetative tissues.

Amino Acid Sequence↗

PubMed1995

Characterization of a maize G-box binding factor that is induced by hypoxia.

G-box cis-acting DNA sequence elements are present in the promoter region of a number of signal-inducible plant genes. In many cases this motif is essential for gene expression. Maize nuclear extracts contain a protein complex that binds specifically to the G-box sequence. Previously, a protein called GF14 was described that is physically associated with the G-box binding complex, but is not a DNA-binding factor in and of itself. This paper reports the isolation of a cDNA encoding a maize G-box binding factor (GBF). The deduced amino acid sequence indicates that maize GBF1 is a basic region-leucine zipper protein. GBF1 binds to the G-box element with specificity similar to that of the binding activity in nuclear extracts. Furthermore, maize GBF1 and the factor detected in nuclear extract are identical in their molecular weight and are immunologically related. GBF1 mRNA accumulates rapidly in hypoxically induced maize cells prior to the increase in Adh1 mRNA levels. Taken together with results that indicate that GBF1 binds to the hypoxia-responsive promoter of maize Adh1, these observations suggest that GBF1 may be one of the factors involved in the activation of Adh1.

Alcohol Dehydrogenase↗

PubMed2003

A new single-locus cytogenetic mapping system for maize (Zea mays L.): overcoming FISH detection limits with marker-selected sorghum (S. propinquum L.) BAC clones.

The development of a cytogenetic map for maize (Zea mays L.) is shown to be feasible by means of a combination of resources from sorghum and oat that overcome limitations of single-copy gene detection. A maize chromosome-addition line of oat, OMAd9.2, provided clear images of optically isolated pachytene chromosomes through a chromosome spread and painting technique. A direct labeled oligonucleotide fluorescence in situ hybridization (FISH) probe MCCY specifically stained the centromere. The arm ratio (long/short) for maize chromosome 9 in the addition line was 1.7, comparable to the range of 1.6-2.1 previously reported for maize chromosome 9. A sorghum (Sorghum propinquum L.) BAC library was screened by hybridization with each of three maize core-bin-marker (CBM) probes: umc109 (CBM9.01), umc192/bz1 (CBM9.02), and csu54b (CBM9.08). A single BAC clone for each marker was chosen; designated sCBM9.1, sCBM9.2, or sCBM9.8; and used as a FISH probe on pachytene spreads from OMAd9.2. In each case, discrete FISH signals were observed, and their cytogenetic positions were determined to be 9S.79 (at position 79% of the length of chromosome 9 short arm) for sCBM9.1, 9S.65 for sCBM9.2, and approximately 9L.95 for sCBM9.8. These map positions were co-linear with linkage-map positions for these and other loci common to the linkage and cytogenetic maps. This work represents a major breakthrough for cytogenetic mapping of the maize genome, and also provides a general strategy that can be applied to cytogenetic mapping of other plant species with relatively large and complex genomes.

Avena↗

PubMedDate not supplied

Gene flow scenarios with transgenic maize in Mexico.

Maize diversity is widespread in Mexico and it has been stewarded by campesinos in small communities until the present. With the arrival of transgenic maize, the objective of this study is to analyze possible scenarios that could result if genetically modified maize were not regulated and openly available in Mexico. By applying a simple logistic model based on the conditions of maize production in Mexico, the dispersion of transgenic maize in different situations within fields of farmers is described. In traditional open systems of freely exchanged seed within communities it is concluded that the most likely outcome of GM maize release is the incorporation of transgenes in the genome of Mexican germplasm and possibly in that of teosinte.

Agriculture↗

PubMedDate not supplied

Diversity of alternative hosts of maize stemborers in Trans-Nzoia district of Kenya.

Genetically-engineered (GE) crops such as those expressing insecticidal Bacillus thuringiensis (Bt) toxin genes have the potential to greatly reduce the use of broad spectrum insecticides and increase crop productivity. However, development of resistance by the target insect species is an important consideration in the deployment of this strategy. In areas where GE crops are deployed on a large scale, current resistance management strategies rely on a 'refuge strategy', comprising the incorporation of a certain proportion of non-GE plants in the agro-ecosystems, to conserve susceptible individuals of the target pests. In the USA, simulation models indicate that at least 20% of the crop should be non-Bt plants. In Africa, the target lepidopteran stemborers attack a wide range of wild grass species as well as cultivated cereal crops. Wild grasses generally occur in the vicinity of maize and other cereal fields, and may provide a refuge if GE crops are in the farming systems. To assess the quality of these grasses as refuges, it is critical to obtain information about their size and spatial distribution. In this study, we have assessed the abundance and diversity of alternative refuge of stemborers, mainly wild grasses occurring in the proximity of maize fields, in Trans-Nzoia district, one of the most important maize growing areas in Kenya. The proportion of wild host plants relative to maize was found to decline from 100% during the non-cropping season to <8% during the maize-growing season. The Shannon-Weaver diversity index indicated high variation in the diversity of wild hosts of stemborers between agro-ecological zones in the district. The results of this study are discussed in light of the possible role that wild host plant species might play in stemborer resistance management following the introduction of Bt maize.

Adaptation, Physiological↗