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PubMed1992

Transgenic maize plants by tissue electroporation.

In this paper, we describe the transformation of regenerable maize tissues by electroporation. In many maize lines, immature zygotic embryos can give rise to embryogenic callus cultures from which plants can be regenerated. Immature zygotic embryos or embryogenic type I calli were wounded either enzymatically or mechanically and subsequently electroporated with a chimeric gene encoding neomycin phosphotransferase (neo). Transformed embryogenic calli were selected from electroporated tissues on kanamycin-containing media and fertile transgenic maize plants were regenerated. The neo gene was transmitted to the progeny of kanamycin-resistant transformants in a Mendelian fashion. This showed that all transformants were nonchimeric, suggesting that transformation and regeneration are a single-cell event. The maize transformation procedure presented here does not require the establishment of genotype-dependent embryogenic type II callus or cell suspension cultures and facilitates the engineering of new traits into agronomically relevant maize inbred lines.

Base Sequence↗

PubMed1993

Expression of the two maize TATA binding protein genes and function of the encoded TBP proteins by complementation in yeast.

A single gene encodes the TATA binding protein (TBP) in yeasts and animals. Although two TBP-encoding genes (Tbp) previously were isolated from both Arabidopsis and maize, the expression and in vivo function of the encoded plant TBPs were not investigated. Here, we report that the two highly conserved maize Tbp genes are unlinked and reside within larger, ancestrally duplicated segments in the genome. We find quantitative differences in Tbp1 versus Tbp2 transcript accumulation in some maize tissues. These nonidentical expression patterns may indicate differences in the tissue-specific regulation of these genes, which might allow the two encoded maize TBP isoforms to perform nonoverlapping functions in the plant. In addition, we show that the maize TBP products, unlike animal TBPs, are functionally interchangeable with yeast TBP for conferring yeast cell viability. This is a conclusive demonstration of in vivo activity for a nonyeast TBP protein, and these complementation results point to particular amino acids in TBP that are likely to influence species-specific protein interactions.

Amino Acid Sequence↗

PubMed1993

Identification and molecular characterization of ZAG1, the maize homolog of the Arabidopsis floral homeotic gene AGAMOUS.

Recent genetic and molecular studies in Arabidopsis and Antirrhinum suggest that mechanisms controlling floral development are well conserved among dicotyledonous species. To assess whether similar mechanisms also operate in more distantly related monocotyledonous species, we have begun to clone homologs of Arabidopsis floral genes from maize. Here we report the characterization of two genes, designated ZAG1 and ZAG2 (for Zea AG), that were cloned from a maize inflorescence cDNA library by low stringency hybridization with the AGAMOUS (AG) cDNA from Arabidopsis. ZAG1 encodes a putative polypeptide of 286 amino acids having 61% identity with the AGAMOUS (AG) protein. Through a stretch of 56 amino acids, constituting the MADS domain, the two proteins are identical except for two conservative amino acid substitutions. The ZAG2 protein is less similar to AG, with 49% identity overall and substantially less similarity than ZAG1 outside the well-conserved MADS domain. Like AG, ZAG1 RNA accumulates early in stamen and carpel primordia. In contrast, ZAG2 expression begins later and is restricted to developing carpels. Hybridization to genomic DNA with the full-length ZAG1 cDNA under moderately stringent conditions indicated the presence of a large family of related genes. Mapping data using maize recombinant inbreds placed ZAG1 and ZAG2 near two loci that are known to affect maize flower development, Polytypic ear (Pt) and Tassel seed4 (Ts4), respectively. The ZAG1 protein from in vitro translations binds to a consensus target site that is recognized by the AG protein. These data suggest that maize contains a homolog of the Arabidopsis floral identity gene AG and that this gene is conserved in sequence and function.

AGAMOUS Protein, Arabidopsis↗

PubMed1987

Efficacy of grass-maize pollen oral immunotherapy in patients with seasonal hay-fever: a double-blind study.

Forty patients with a well-documented history of seasonal hay fever and a positive skin-prick test specific to grass pollen, including Bermuda grass and maize pollen (Zea maize), were allocated randomly on a double-blind basis to receive either an oral mixed grass-maize pollen extract or a matched placebo during the 1981/1982 grass pollen season. After 12 months the code was broken and patients on placebo were transferred to active therapy while patients on active therapy continued with maintenance therapy for another 12 months during the 1982/1983 grass pollen season. The assessment of the effect of the orally administered grass-maize pollen extract was on the clinical symptoms. During the first year the patients on active therapy had significantly fewer hay fever symptoms during the summer months compared with the placebo group. During the second study year, with all patients on active therapy, both groups had markedly milder symptoms compared with the placebo group. Side-effects were negligible. This study concludes that oral immunotherapy with grass-maize pollen extract in grass pollen-sensitive seasonal hay fever patients is safe and effective.

Administration, Oral↗

PubMed2006

Impact of Bt maize pollen (MON810) on lepidopteran larvae living on accompanying weeds.

Environmental risks of Bt maize, particularly pollen drift from Bt maize, were assessed for nontarget lepidopteran larvae in maize field margins. In our experimental approach, we carried out 3-year field trials on 6 ha total. Three treatments were used in a randomized block design with eight replications resulting in 24 plots: (i) near-isogenic control variety without insecticide (control), (ii) near-isogenic control variety with chemical insecticide (Baytroid) and (iii) Bt maize expressing the recombinant toxin. We established a weed strip (20 x 1 m) in every plot consisting of a Chenopodium album (goosefoot)/Sinapis alba (mustard) mixture. In these strips we measured diversity and abundance of lepidopteran larvae during maize bloom and pollen shed. C. album hosted five species but all in very low densities; therefore data were not suitable for statistical analysis. S. alba hosted nine species in total. Most abundant were Plutella xylostella and Pieris rapae. For these species no differences were detected between the Bt treatment and the control, but the chemical insecticide treatment reduced larval abundance significantly. Conclusions regarding experimental methodology and results are discussed in regard to environmental risk assessment and monitoring of genetically modified organisms.

Animals↗

PubMed1987

A study on the heterogeneity of histone H1 from dry maize embryos.

Maize dry embryo cells have been chosen as model for the study of H1 histone complement of metabolically inactive plant chromatin. H1 has been fractionated into two distinct bands in acetic acid/urea gels. Analysis of each of these bands in SDS-containing gels has shown that maize embryo H1 is heterogeneous, consisting of at least six proteins. Cross-reactivity of maize H1 species with antibodies against mouse liver total H1 and against its individual variants indicates that they share common immunological determinants but differ substantially from each other when compared by peptide mapping. It is concluded that a couple of the plant H1 subfractions are related to animal H1A histone and that another one is related to H1B histone. The other three maize H1 variants are closely related to each other and they also share common immunological determinants with mouse H1A, and possibly with H1B. All maize H1 species slightly cross-react with antibodies against H1 degree, suggesting that no one of the plant subfractions could be characterized as H1 degree in particular. One of the proteins co-extracted and comigrating with H1 is most probably an embryo storage protein.

Animals↗

PubMed2004

Chaperone activity of recombinant maize chloroplast protein synthesis elongation factor, EF-Tu.

The protein synthesis elongation factor, EF-Tu, is a protein that carries aminoacyl-tRNA to the A-site of the ribosome during the elongation phase of protein synthesis. In maize (Zea mays L) this protein has been implicated in heat tolerance, and it has been hypothesized that EF-Tu confers heat tolerance by acting as a molecular chaperone and protecting heat-labile proteins from thermal aggregation and inactivation. In this study we investigated the effect of the recombinant precursor of maize EF-Tu (pre-EF-Tu) on thermal aggregation and inactivation of the heat-labile proteins, citrate synthase and malate dehydrogenase. The recombinant pre-EF-Tu was purified from Escherichia coli expressing this protein, and mass spectrometry confirmed that the isolated protein was indeed maize EF-Tu. The purified protein was capable of binding GDP (indicative of protein activity) and was stable at 45 degrees C, the highest temperature used in this study to test this protein for possible chaperone activity. Importantly, the recombinant maize pre-EF-Tu displayed chaperone activity. It protected citrate synthase and malate dehydrogenase from thermal aggregation and inactivation. To our knowledge, this is the first observation of chaperone activity by a plant/eukaryotic pre-EF-Tu protein. The results of this study support the hypothesis that maize EF-Tu plays a role in heat tolerance by acting as a molecular chaperone and protecting chloroplast proteins from thermal aggregation and inactivation.

Amino Acid Sequence↗

PubMed2005

The efficacy of a modified aluminosilicate as a detoxifying agent in Fusarium toxin contaminated maize containing diets for piglets.

Two feeding experiments with female weaned piglets were carried out applying a complete two by two factorial design to investigate the effects of the dietary inclusion of 500 g/kg Fusarium toxin contaminated maize (8.6 mg/kg deoxynivalenol (DON); 1.2 mg/kg zearalenone (ZON)) and of 4 g/kg aluminosilicate (AS) as a detoxifying agent. The resulting four diets were fed ad libitum to a total of 80 piglets (20 piglets per group, allotted to a total of 20 pens) covering a live weight range of 10.5 +/- 1.3 to 27.5 +/- 4.4 kg in experiment 1, and to a total of 48 piglets (12 piglets per group, allotted to 12 pens) covering a live weight range of 9.7 +/- 1.8 to 21.4 +/- 4.8 kg in experiment 2. The animals of experiment 1 were slaughtered on days 34-36 of feeding the experimental diets. The mycotoxin analyses revealed that the control maize also contained considerable concentrations of Fusarium toxins, but the differences in DON and ZON concentrations between control and contaminated diets were sufficiently high to demonstrate both dose-related toxin effects. Voluntary feed intake and live weight gain of the animals were significantly reduced by the inclusion of Fusarium toxin contaminated maize into the diets in both experiments, while a significantly decreased feed to gain ratio was found in experiment 1. Furthermore, the relative weight of the uterus, stomach and heart of the animals fed the contaminated maize containing diets were significantly increased. Serum albumin concentrations and the activity of GLDH were significantly reduced by the inclusion of the contaminated maize. The addition of AS to the Fusarium toxin contaminated diets did not prevent or alleviate any of the mentioned effects. Moreover, the feed intake tended to be decreased by this supplementation in both experiments, while a significantly decreased feed to gain ratio was indicated for this factor in experiment one as well. The serum concentration of albumin and the activities of ASAT and gammaGT were significantly increased if AS was present in the diets while serum concentration of cholesterol and alpha-tocopherol were decreased significantly or in tendency, respectively. The concentrations of retinol and retinyl esters in liver and serum were not altered by the treatments. The analysed concentrations of zearalenone (ZON) and its metabolites in the bile fluid clearly indicated the differences in dietary ZON concentrations and showed that AS was ineffective in preventing the absorption of the toxin from the gastrointestinal tract. Also, serum concentrations of DON reflected the DON intake prior to sampling. However, there were no differences between groups fed diets with or without AS which also suggests the inefficacy of the tested AS in preventing the DON absorption. The present investigations failed to demonstrate a detoxifying capacity of the tested additive and emphasize the general necessity for a critical verification of detoxifying agents in vivo.

Aluminum Silicates↗

PubMed2004

Engineering of enhanced glycine betaine synthesis improves drought tolerance in maize.

Glycine betaine plays an important role in some plants, including maize, in conditions of abiotic stress, but different maize varieties vary in their capacity to accumulate glycine betaine. An elite maize inbred line DH4866 was transformed with the betA gene from Escherichia coli encoding choline dehydrogenase (EC 1.1.99.1), a key enzyme in the biosynthesis of glycine betaine from choline. The transgenic maize plants accumulated higher levels of glycine betaine and were more tolerant to drought stress than wild-type plants (non-transgenic) at germination and the young seedling stage. Most importantly, the grain yield of transgenic plants was significantly higher than that of wild-type plants after drought treatment. The enhanced glycine betaine accumulation in transgenic maize provides greater protection of the integrity of the cell membrane and greater activity of enzymes compared with wild-type plants in conditions of drought stress.

Journal Article↗

PubMed2005

Household dietary strategies to enhance the content and bioavailability of iron, zinc and calcium of selected rice- and maize-based Philippine complementary foods.

Philippine complementary foods are predominantly plant-based, with a low content of readily available iron, zinc, and calcium, and a relatively high amount of phytate, a potent inhibitor of mineral absorption. Some of the phytate is water soluble, and hence can be removed by soaking. In this study we have compared the iron, zinc, and calcium content, and estimated iron and zinc bioavailability of rice- and maize-based Filipino complementary foods prepared with and without soaking and/or enrichment with chicken liver, egg yolk, small soft-boned fish, and mung bean grits. Analysis of iron, zinc, and calcium were performed by atomic absorption spectrometry, and phytate (based on hexa-(IP6) and penta-inositol phosphate (IP5) by HPLC; corresponding [Phy]/[Fe] and [Phy]/[Zn] molar ratios were calculated as predictors of iron and zinc bioavailability. Addition of chicken liver, followed by egg yolk, resulted in the greatest increases in iron and zinc content for both the rice- and maize-based complementary foods, whereas addition of small dried fish with bones had the greatest effect on calcium. The IP5 + IP6 content and [Phy]/[Zn] molar ratios were higher in the maize- than rice-based complementary foods, and were reduced by soaking, although only the maize plus mung bean grits, with and without soaking, had [Phy]/[Zn] molar ratios above 15. Enrichment with animal protein or soaking has the potential to enhance the content of absorbable iron, zinc, and probably calcium to varying degrees in rice- and maize-based Philippine complementary foods.

Biological Availability↗

PubMed1970

Chromosome pairing within genomes in maize-Tripsacum hybrids.

When the ten chromosomes of maize were inserted inlto a polyploid (2n = 72) Tripsacum dactyloides background they formed up to five pairs at meiosis. Two plants that each contained 36 Tripsacum and 14 maize chromosomes were deprived from the F(1) of maize x Tripsacum. Chromo. somes of these plants frequently formed 25 bivalents, 18 between Tripsacum chromosomes and seven between maize chromosomes. Maize chromosomes could be distinguished from Tripsacum chromosomes on the basis of size. The withint-genome pairing is probably induced by the genetic background.

Chromosomes↗

PubMed2007

Reduced contamination by the Fusarium mycotoxin zearalenone in maize kernels through genetic modification with a detoxification gene.

Maize is subject to ear rot caused by toxigenic Aspergillus and Fusarium species, resulting in contamination with aflatoxins, fumonisins, trichothecenes, and zearalenone (ZEN). The trichothecene group and ZEN mycotoxins are produced by the cereal pathogen Fusarium graminearum. A transgenic detoxification system for the elimination of ZEN was previously developed using an egfp::zhd101 gene (gfzhd101), encoding an enhanced green fluorescent protein fused to a ZEN-degrading enzyme. In this study, we produced a transgenic maize line expressing an intact copy of gfzhd101 and examined the feasibility of transgene-mediated detoxification in the kernels. ZEN-degrading activity has been detected in transgenic kernels during seed maturation (for a period of 6 weeks after pollination). The level of detoxification activity was unaltered after an additional storage period of 16 weeks at 6 degrees C. When the seeds were artificially contaminated by immersion in a ZEN solution for 48 h at 28 degrees C, the total amount of the mycotoxin in the transgenic seeds was uniformly reduced to less than 1/10 of that in the wild type. The ZEN in the transgenic maize kernels was also efficiently decontaminated under conditions of lower water activity (aw) and temperature; e.g., 16.9 microg of ZEN was removed per gram of seed within 48 h at an aw of 0.90 at 20 degrees C. F. graminearum infection assays demonstrated an absence of ZEN in the transgenic maize seeds, while the mycotoxin accumulated in wild-type kernels under the same conditions. Transgene-mediated detoxification may offer simple solutions to the problems of mycotoxin contamination in maize.

Biotechnology↗

PubMed1990

Digestion of barley, maize, and wheat by selected species of ruminal bacteria.

Differences in the digestion of barley, maize, and wheat by three major ruminal starch-digesting bacterial species, Streptococcus bovis 26, Ruminobacter amylophilus 50, and Butyrivibrio fibrisolvens A38, were characterized. The rate of starch digestion in all cereal species was greater for S. bovis 26 than for R. amylophilus 50 or B. fibrisolvens A38. Starch digestion by S. bovis 26 was greater in wheat than in barley or maize, whereas starch digestion by R. amylophilus 50 was greater in barley than in maize or wheat. B. fibrisolvens A38 digested the starch in barley and maize to a similar extent but was virtually unable to digest the starch in wheat. The higher ammonia concentration in cultures of B. fibrisolvens A38 when grown on wheat than when grown on barley or maize suggests that B. fibrisolvens A38 utilized wheat protein rather than starch. Scanning electron microscopy revealed that B. fibrisolvens A38 initially colonized cell wall material, while S. bovis 26 randomly colonized the endosperm and R. amylophilus 50 preferentially colonized starch granules. There was subsequent colonization but only superficial digestion of wheat starch granules by B. fibrisolvens A38. Variation in the association between starch and protein within the endosperm of cereal grains contributes to the differential effectiveness with which amylolytic species can utilize cereal starch.

Journal Article↗

PubMed1996

Root colonization of maize and lettuce by bioluminescent Rhizobium leguminosarum biovar phaseoli.

Two strains of Rhizobium leguminosarum bv. phaseoli and three other plant growth-promoting rhizobacteria (PGPR) were examined for the potential of maize and lettuce root colonization. All of these strains were selected in vitro for their phosphate-solubilizing abilities. Maize and lettuce seeds were treated with derivatives of all strains marked with lux genes for bioluminescence and resistance to kanamycin and rifampin prior to planting in nonsterile Promix and natural soil. The introduced bacterial strains were quantified on roots by dilution plating on antibiotic media together with observation of bioluminescence. Rhizobia were superior colonizers compared with other tested bacteria; rhizobial root populations averaged log 4.1 CFU/g (fresh weight) on maize roots 4 weeks after seeding and log 3.7 CFU/g (fresh weight) on lettuce roots 5 weeks after seeding. The average populations of the recovered PGPR strains were log 3.5 and log 3.0 CFU/g (fresh weight) on maize and lettuce roots, respectively. One of the three PGPR was not recovered later than the first week after seeding in Promix. Bioluminescence also permitted visualization of in situ root colonization in rhizoboxes and demonstrated the efficiency of rhizobial strains to colonize and survive on maize and lettuce roots.

Lactuca↗

PubMed1999

Influence of kernel age on fumonisin B1 production in maize by Fusarium moniliforme.

Production of fumonisins by Fusarium moniliforme on naturally infected maize ears is an important food safety concern due to the toxic nature of this class of mycotoxins. Assessing the potential risk of fumonisin production in developing maize ears prior to harvest requires an understanding of the regulation of toxin biosynthesis during kernel maturation. We investigated the developmental-stage-dependent relationship between maize kernels and fumonisin B1 production by using kernels collected at the blister (R2), milk (R3), dough (R4), and dent (R5) stages following inoculation in culture at their respective field moisture contents with F. moniliforme. Highly significant differences (P </= 0.001) in fumonisin B1 production were found among kernels at the different developmental stages. The highest levels of fumonisin B1 were produced on the dent stage kernels, and the lowest levels were produced on the blister stage kernels. The differences in fumonisin B1 production among kernels at the different developmental stages remained significant (P </= 0.001) when the moisture contents of the kernels were adjusted to the same level prior to inoculation. We concluded that toxin production is affected by substrate composition as well as by moisture content. Our study also demonstrated that fumonisin B1 biosynthesis on maize kernels is influenced by factors which vary with the developmental age of the tissue. The risk of fumonisin contamination may begin early in maize ear development and increases as the kernels reach physiological maturity.

Carboxylic Acids↗

PubMed1997

A heterologous maize rpoB editing site is recognized by transgenic tobacco chloroplasts.

Single nucleotides in plant chloroplast transcripts are edited from the genomically encoded C to U, often resulting in changes of the encoded protein sequence. Site-specific trans-acting factors are postulated to direct the selection of edited residues. In order to further define cis sequences required for RNA editing, we investigated whether two editing sites present in maize rpoB mRNA would be recognized by the editing machinery of transformed tobacco chloroplasts. A 93-nucleotide (nt) segment surrounding site I is sufficient to direct editing of the maize sequence in tobacco chloroplasts. However, an 86-nt segment surrounding maize site IV (which is genomically encoded as a T in tobacco) does not confer editing of this site, suggesting that trans-acting factors necessary for recognition of site IV are not present in tobacco. The maize sequences surrounding site I were found to compete with the endogenous rpoB for a depletable trans factor and to reduce editing of endogenous site I. The presence of exogenous maize site I was also found to decrease editing of endogenous tobacco site II, indicating that there is a shared aspect of editing for some closely spaced editing sites.

Base Sequence↗

PubMed1993

Mapping maize microsatellites and polymerase chain reaction confirmation of the targeted repeats using a CT primer.

Microsatellites, also called simple sequence repeats (SSRs), have yielded an important class of DNA markers most notable for mapping mammalian genomes. To study the occurrence of microsatellites and their inheritance in maize, a search was made of 280 maize GenBank sequences. Six SSRs were chosen and unique flanking primers were designed for polymerase chain reaction (PCR) amplification. Eight different maize inbreds were studied with these six primer pairs and a mean of 3.5 polymorphic patterns occurred within the expected size range. For five of these putative microsatellites, the segregation in a maize restriction fragment length polymorphism mapping population was analyzed. Four of the microsatellites cosegregated with the Adh1, Gpc1, Pdk1, and Tpi genes from which the primer sequences were derived. The fifth primer pair (MZEGPA1) showed segregating polymorphisms, but the products were larger than expected. To verify the existence of the original SSRs in the segregating PCR products, a CT primer, containing a CT SSR and an arbitrary leader sequence, was used to reamplify these products. The four microsatellites that cosegregated with the original gene were reamplified as anticipated, whereas a suspicious 230-bp product obtained when using the MZEGPA1 primers could not be reamplified. Based on these results it is concluded that microsatellites can be a valuable tool for maize mapping.

Base Sequence↗

PubMed2002

Opportunities for nutritionally enhanced maize and wheat varieties to combat protein and micronutrient malnutrition.

Naturally occurring variation detected in the germplasm of maize and wheat, two of the top three cereal crops in the world, provides options for incorporating higher levels of iron, zinc, and beta-carotene into these grains. In addition, quality protein maize (QPM) has been developed from naturally occurring variation; its seed contains enhanced levels of lysine and tryptophan, two essential amino acids lacking in cereals. The International Maize and Wheat Improvement Center, along with its many partners, has identified several maize and wheat varieties with 25% to 30% higher grain iron and zinc concentrations. Wild relatives of wheat have been found to contain some of the highest iron and zinc concentrations in the grains. Although these accessions are often low yielding and have poor grain quality, backcrossing to bread wheat could result in highly nutritious cultivars. Options are now available for conventional and biotechnology-assisted improvement of the nutritional content of maize and wheat germplasm.

Biotechnology↗