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PubMed2003

Structure and evolution of the Cinful retrotransposon family of maize.

A maize cDNA clone was isolated by virtue of its intense hybridization to total maize genomic DNA, indicating homology to highly repetitive sequences. Genomic homologues were identified and subcloned from an adh1-bearing maize yeast artificial chromosome (YAC). Sequencing revealed that the expressed sequence was part of a Ty3-gypsy-type retrotransposon. We discovered and sequenced two complete retrotransposons of this family, and named them Cinful elements because they are members of a family of maize retrotransposons including Zeon-1 and the first plant transposable element sequenced, the solo long terminal repeat (LTR) called Cin1. All are defective, as Cinful-1 and Cinful-2 elements lack gag and Zeon-1 lacks pol homology. Despite the apparent lack of an intact "autonomous" element, the Cinful family has expanded to a copy number of about 18 000, representing just under 9% of the maize genome. Both point mutations and major rearrangements, including possible gene acquisition, differentiate members of the Cinful family. Cinful family members were found to have an unusual feature that we also observed in two other Ty3-class retrotransposons of teosinte and tobacco: related tandem repeats that separate their internal domains with a gag- or pol-containing homology from a 3' segment of unknown function. The conserved and variable features identified provide insights into the origin, mutational history, and functional components of this major constituent of the maize genome.

Amino Acid Sequence↗

PubMed2004

Confocal analysis of chromosome behavior in wheat x maize zygotes.

Herein, we profile the first embryonic mitosis in a hybrid of wheat and maize by using a whole-mount genomic in situ hybridization method and immunofluorescence staining with a tubulin-specific antibody. We have successfully captured the dynamics of each set of parental chromosomes in the first zygotic division of the hybrid embryo 24-28 h after crossing. During the first zygotic metaphase, although both sets of parental chromosomes congressed into the equatorial plate of the zygote, the maize chromosomes tended to lag in comparison with the wheat chromosomes. During anaphase, each parental chromosome separated into its sister chromosomes; however, some of the maize chromosomes lagged around the metaphase plate as segregants. The maize sister chromosomes that did move toward the pole showed delayed and asymmetric movement as compared with the wheat ones. Immunological staining of tubulin revealed a bipolar spindle structure in the first zygotic metaphase. The kinetochores of the maize chromosomes that lagged around the metaphase plate did not attach to the spindle microtubules. These results suggest that factors on the kinetochores of maize chromosomes that are required to control chromosome movement are deficient in the zygotic cell cycle.

Chromosomes, Plant↗

PubMed2002

A N2-fixing endophytic Burkholderia sp. associated with maize plants cultivated in Mexico.

In the frame of a survey of potentially endophytic N2-fixing Burkholderia associated with maize in Mexico, its country of origin, the soil of an indigenous maize field near Oaxaca was studied. Under laboratory conditions, plant seedlings of two ancient maize varieties were used as a trap to select endophyte candidates from the soil sample. Among the N2 fixers isolated from inside plant tissues and able to grow on PCAT medium, the most abundant isolates belonged to genus Burkholderia (API 20NE, rrs sequences). Representative isolates obtained from roots and shoots of different plants appeared identical (rrs and nifH RFLP), showing that they were closely related. In addition, their 16S rDNA sequences differed from described Burkholderia species and, phylogenetically, they constituted a separate deep-branching new lineage in genus Burkholderia. This indicated that these isolates probably constituted a new species. An inoculation experiment confirmed that these N2-fixing Burkholderia isolates could densely colonize the plant tissues of maize. More isolates of this group were subsequently obtained from field-grown maize and teosinte plants. It was hypothesized that strains of this species had developed a sort of primitive symbiosis with one of their host plants, teosinte, which persisted during the domestication of teosinte into maize.

Bacteriological Techniques↗

PubMed2004

Conservation of B-class floral homeotic gene function between maize and Arabidopsis.

The ABC model of flower development, established through studies in eudicot model species, proposes that petal and stamen identity are under the control of B-class genes. Analysis of B- and C-class genes in the grass species rice and maize suggests that the C- and B-class functions are conserved between monocots and eudicots, with B-class genes controlling stamen and lodicule development. We have undertaken a further analysis of the maize B-class genes Silky1, the putative AP3 ortholog, and Zmm16, a putative PI ortholog, in order to compare their function with the Arabidopsis B-class genes. Our results show that maize B-class proteins interact in vitro to bind DNA as an obligate heterodimer, as do Arabidopsis B-class proteins. The maize proteins also interact with the appropriate Arabidopsis B-class partner proteins to bind DNA. Furthermore, we show that maize B-class genes are capable of rescuing the corresponding Arabidopsis B-class mutant phenotypes. This demonstrates B-class activity of the maize gene Zmm16, and provides compelling evidence that B-class gene function is conserved between monocots and eudicots.

Arabidopsis↗

PubMed2001

Exposure of rural and urban populations in KwaZulu Natal, South Africa, to fumonisin B(1) in maize.

We surveyed households in rural and urban areas of KwaZulu Natal, South Africa, to assess the exposure of the inhabitants to fumonisin B(1) (FB(1)), a mycotoxin produced by Fusarium verticillioides. In southern African regions maize, used as a staple food by the population, is prone to F. verticillioides infection. Furthermore, high levels of FB(1) in maize have been associated with esophageal cancer in South Africa. We assessed exposure of the population to FB(1) at three levels, namely, by analyzing stored maize, plate-ready food, and feces. The positions of participating households in the rural area were recorded using geographic information systems (GIS) for ease and accuracy of follow-up. Of the 50 rural maize samples examined, 32% had levels of FB(1) ranging from 0.1-22.2 mg/kg, whereas 29% of the 28 cooked maize (phutu) samples contained FB(1) ranging from 0.1-0.4 mg/kg. The incidence and levels of FB(1) in feces were 33% and 0.5-39.0 mg/kg, respectively. Of the 49 urban maize samples analyzed 6.1% had a range of 0.2-0.5 mg/kg FB(1), whereas 3 of 44 fecal samples (6%) ranged between 0.6 and 16.2 mg/kg. No FB(1) was detected in urban phutu samples. Because these levels are lower than those published from regions in South Africa with high incidence of esophageal cancer, it may be concluded that the risk of esophageal cancer from FB(1) exposure is lower in the KwaZulu Natal region.

Carboxylic Acids↗

PubMed2003

RescueMu protocols for maize functional genomics.

RescueMu is a modified Mu1 transposon transformed into maize to permit mutagenesis and subsequent recovery of mutant alleles by plasmid rescue. RescueMu elements insert late in the germline as well as in terminally dividing somatic (e.g., leaf) cells. Germinal insertions may result in a mutant phenotype, and RescueMu permits recovery of 5-25 kb of transposon-flanking genomic DNA without having to construct and screen genomic DNA libraries. Late somatic insertions of RescueMu do not result in a visible phenotype, but they are instead used to construct plasmid libraries of gene-enriched maize genomic DNA to facilitate the identification and sequencing of the euchromatic portion of the maize genome. This is because maize leaves contain abundant independent RescueMu somatic insertions, and 70-90% of these insertions occur preferentially into genes and not repetitive DNA. This chapter describes detailed protocols on how to obtain, generate, and use RescueMu for maize genomics, including resources developed by the Maize Gene Discovery Project (MGDP) consortium available online at ZmDB.

DNA Transposable Elements↗

PubMedDate not supplied

Effects of supplementary ultraviolet-B irradiance on maize yield and qualities: a field experiment.

Stratospheric ozone depletion has caused an increase in the amount of ultraviolet-B (UV-B) radiation reaching the earth's surface. Numerous investigations have demonstrated that the effect of UV-B enhancements on plants includes reduction in grain yield, alteration in species competition, susceptibility to disease and changes in plant structure and pigmentation. Many experiments examining UV-B radiation effects on plants have been conducted in growth chambers or greenhouses. It has been questioned whether the effect of UV-B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV-B/ultraviolet-A radiation (320-400 nm) and UV-B/photosynthetically active radiation (PAR) in many indoor studies. Field studies on UV-B radiation effect on plants have been recommended to use the UV and PAR irradiance provided by natural light. This study reports the growth and yield responses of a maize crop exposed to enhanced UV-B radiation and the UV-B effects on maize seed qualities under field conditions. Enhanced UV-B radiation caused a significant reduction in the dry matter accumulation and the maize yield in turn was affected. With increased UV-B radiation the flavonoid accumulation in maize leaves increased and the contents of chlorophyll a, b and (a + b) of maize leaves were reduced. The levels of protein, sugar and starch of maize seed decreased with enhanced UV-B radiation, whereas the level of lysine increased with enhanced UV-B radiation.

Flowers↗

PubMed2006

Relative fitness of transgenic vs. non-transgenic maize x teosinte hybrids: a field evaluation.

Concern has been often expressed regarding the impact and persistence of transgenes that enter wild populations via gene flow. The impact of a transgene and its persistence are largely determined by the relative fitness of transgenic hybrids and hybrid derivatives compared to non-transgenic plants. Nevertheless, few studies have addressed this question experimentally in the field. Despite the economic importance of maize, and the fact that it naturally hybridizes with the teosinte taxon Zea mays ssp. mexicana, sometimes known as "chalco teosinte," the question has received little experimental attention in this system. Using a glyphosate-tolerant maize cultivar and chalco teosinte as parental lines, we carried out a field experiment testing (1) the relative fitness of maize x teosinte hybrids, compared to their parental taxa, as well as (2) the relative fitness of transgenic hybrids compared to non-transgenic hybrids created from the same parental stock. In order to evaluate the influence of the transgenic construct in different genetic backgrounds, our study included transgenic and non-transgenic pure maize progeny from the cultivar as well. We measured both vegetative and reproductive parameters. Our results demonstrated that hybrids have greater vigor and produced more seeds than the wild parent. However, in the absence of selective pressure from glyphosate herbicide, we did not observe any direct positive or negative impact of the transgene on the fitness or vigor of either the hybrids or pure maize progeny. We discuss our results in terms of the potential for spontaneous transgene flow and introgression from transgenic maize into sympatric teosinte.

Germination↗

PubMed2001

Effect of partial replacement of oats with sugar beet pulp and maize oil on nutrient utilisation in horses.

The objective of the present work was to assess the influence of partial replacement of oats with dried unmolassed sugar beet pulp (SBP) and/or maize oil on nutrient utilisation in horses fed a traditional hay and concentrate diet. The total tract digestibility of nutrients, urinary excretion and plasma parameters were studied in a 4 x 4 Latin-square design experiment with purebred Arabian geldings. Horses fed the SBP diets responded with a reduced (P<0.05) apparent digestibility of crude protein and feeding of maize oil resulted in an increased (P<0.05) apparent digestibility of crude fat. The apparent energy digestibility was unaffected by the replacement of oats with SBP, but increased (P<0.05) when maize oil replaced part of the oats. The urinary excretion of nitrogen increased (P<0.05) when maize oil replaced oats and the excretion of energy was higher (P<0.05) on the diets where oats were replaced by maize oil and SBP. There was a significant (P<0.05) effect across treatments of postprandial blood sampling time on plasma glucose and insulin concentrations. Also, plasma concentrations of glucose and insulin tended to be higher on the oats than on the SBP diets. In conclusion, the limited effects on the digestibility of nutrients and energy suggest that it should be possible to partially replace oats with maize oil and/or SBP in diets for horses without any impairing effects on the overall nutrient utilisation. However, the dietary-induced changes in the urinary excretion of energy and on plasma glucose and insulin levels, indicate a possible influence of dietary carbohydrate composition on nutrient utilisation at the organ level, which requires further study.

Animal Feed↗

PubMed2001

[A detection method for recombinant DNA from genetically modified maize CBH351].

A method using polymerase chain reaction (PCR) was designed for the detection of genetically modified maize CBH351, which has not authorized as safe for use in foods and feeds in Japan yet. We analyzed a recombinant DNA (r-DNA) sequence introduced into CBH351 maize and designed specific primer pairs to amplify a segment including part of the r-DNA. The PCR products obtained by using the designed primer pairs are specific for CBH351 and should prevent false positive results caused by other maizes and other main cereal crops. The r-DNA introduced into CBH351 could be detected from maize samples containing 0.05-0.1% CBH351 maize. This sensitivity is theoretically equivalent to a level of several genome copies and so this technique is a very efficient means to detect CBH351 maize.

DNA Primers↗

PubMedDate not supplied

Enhanced development in nature of larval Anopheles arabiensis mosquitoes feeding on maize pollen.

To determine whether pollen produced by maize (Zea m. mays) may contribute to the development of larval Anopheles gambiae complex mosquitoes, the main African vectors of malaria, we correlated duration of larval development, pupation success, and size of the resulting adults with degree of access to this potential nutriment. Maize pollen is abundant during the wet season on the surface of water near maize plantings in a malaria-endemic region of Ethiopia, and larval Anopheles arabiensis readily ingest these particles in nature. Larvae develop to the pupal stage more rapidly, more frequently, and produce larger adults where maize pollen is abundant than do those that have little access to this food. The force of transmission of malaria in sub-Saharan Africa might be reduced if maize plantings were excluded from the immediate vicinity of homes or, perhaps, if pollen of such maize were to express entomotoxins.

Animals↗

PubMed2005

Reduction of fumonisin B1 and zearalenone by lactic acid bacteria in fermented maize meal.

Fusarium species are fungi that infect maize products worldwide and elaborate mycotoxins, which have been associated with cancer. This study was carried out to investigate the potential of lactic acid bacteria fermentation in reducing mycotoxin concentration and toxicity in maize meal products. Maize meal was spiked separately with fumonisin B1 and zearalenone and then allowed to ferment for 4 days. The potential cytotoxicity of the mycotoxin-spiked fermented extracts was also investigated using the SNO human esophageal carcinoma cell line (the SNO cell line was explanted from a cancer patient, S.N., a 62-year-old Zulu man, in July 1972). A significant decrease (P < 0.05) in the concentration of the two mycotoxins was observed, with a 56 to 67% and a 68 to 75% reduction in the third and fourth days, respectively. The two mycotoxins were not detectable in commercially fermented maize meal (amahewu) samples. After fermentation, mycotoxin-spiked maize meal samples containing lactic acid bacteria culture were comparatively less toxic to SNO cells than were samples without lactic acid bacteria. However, this difference in toxicity was not significant (P > 0.05). These results indicate that lactic acid bacteria fermentation can significantly reduce the concentration of mycotoxins in maize. However, such a reduction may not significantly alter the possible toxic effects of such toxins. The exact mechanism of toxin reduction warrants further investigation.

Consumer Product Safety↗

PubMed1999

Cloning and characterization of a maize cytochrome-b5 reductase with Fe3+-chelate reduction capability.

We previously purified an NADH-dependent Fe3+-chelate reductase (NFR) from maize roots with biochemical features of a cytochrome-b5 reductase (b5R) [Sparla, Bagnaresi, Scagliarini and Trost (1997) FEBS Lett. 414, 571-575]. We have now cloned a maize root cDNA that, on the basis of sequence information, calculated parameters and functional assay, codes for NFR. Maize NFR has 66% and 65% similarity to mammal and yeast b5R respectively. It has a deduced molecular mass of 31.17 kDa and a pI of 8.53. An uncharged region is observed at its N-terminus but no myristoylation consensus site is present. Taken together, these results, coupled with previous biochemical evidence, prove that NFR belongs to the b5R class and document b5R from a plant at the molecular level for the first time. We have also identified a putative Arabidopsis thaliana NFR gene. Its organization (nine exons) closely resembles mammalian b5Rs. Several NFR isoforms are expected to exist in maize. They are probably not produced by alternative translational mechanisms as occur in mammals, because of specific constraints observed in the maize NFR cDNA sequence. In contrast with yeast and mammals, tissue-specific and various subcellular localizations of maize b5R isoforms could result from differential expression of the various members of a multigene family. The first molecular characterization of a plant b5R indicates an overall remarkable evolutionary conservation for these versatile reductase systems. In addition, the well-characterized Fe3+-chelate reduction capabilities of NFR, in addition to known Fe3+-haemoglobin reduction roles for mammal b5R isoforms, suggest further and more generalized roles for the b5R class in endocellular iron reduction.

Amino Acid Sequence↗

PubMed2000

Short-term nitrogen-induced modulation of phosphoenolpyruvate carboxylase in tobacco and maize leaves.

Untransformed maize and tobacco plants and tobacco plants constitutively expressing nitrate reductase were grown with sufficient NO(3)- to support maximal growth. Four days prior to treatment the tobacco plants were deprived of nitrogen. Excised maize leaves and tobacco leaf discs were fed with either 40 mM KNO(3) or 40 mM KCl (control) in the light. Phosphoenolpyruvate (PEP) carboxylase (Case) activity was measured at 0.3 mM and 3 mM PEP. The light- induced increase in PEPCase V(max) was greater in maize than tobacco. Furthermore light decreased malate sensitivity in maize (which was N-replete) but not in N-deficient tobacco. NO(3)- treatment increased PEPCase V:(max) values in both species and decreased the sensitivity to inhibition by malate, but effects of NO(3)- were much more pronounced in tobacco than maize. PEPCase kinase activity was, however, greater in maize leaves NO(3)- than in the Cl(-)-treated controls, suggesting that it is responsive to leaf nitrogen supply. A correlation between foliar glutamine content and PEPCase activity was observed. It is concluded that PEPCase is sensitive to N metabolites which favour increased flow through the anapleurotic pathway in both C(3) and C(4) plants.

Nitrates↗

PubMed2000

[Dynamics of soil P pool in a long-term fertilizing experiment of wheat-maize rotation. I. Crop yield effect of fertilizer P and dynamics of soil total P and inorganic P].

The effects of long-term applying fertilizer P and manure on the pools of soil total P and inorganic P and the crop yield in rotation of winter wheat-summer maize-->spring maize were studied. The results showed that the pool of soil total P and inorganic P were increased by applying fertilizer P and manure, and the phosphorus mostly accumulated in soil was inorganic P. The critical amounts of fertilizer P (P2O5) for balancing soil P were 94.7 kg.hm-2 to winter wheat-summer maize and 51.5 kg.hm-2 to spring maize. Based on regression equations, the application rates of fertilizer P (P2O5) for economic optimum and highest yields were 135.8 and 149.8 kg.hm-2 to winter wheat-summer maize, and 88.6 and 95.9 kg.hm-2 to spring maize, respectively.

China↗

PubMedDate not supplied

Novel reference molecules for quantitation of genetically modified maize and soybean.

New quantitation methods based on a real-time polymerase chain reaction (PCR) technique were developed for 5 lines of genetically modified (GM) maize, including MON810, Event176, Bt11, T25, and GA21, and a GM soy, Roundup Ready. Oligonucleotide DNA, including specific primers and fluorescent dye-labeled probes, were designed for PCRs. Two plasmids were constructed as reference molecules (RMs) for the detection of GM maize and GM soy. The molecules contain the DNA sequences of a specific region found in each GM line, universal sequences used in various GM lines, such as cauliflower mosaic virus 35S promoter and nopaline synthase terminator, and the endogenous DNA sequences of maize or soy. By using these plasmids, no GM maize and GM soy were required as reference materials for the qualitative and quantitative PCR technique. Test samples containing 0, 0.10, 0.50, 1.0, 5.0, and 10% GM maize or GM soy were quantitated. At the 5.0% level, the bias (mean-true value) ranged from 2.8 to 19.4% and the relative standard deviation was <5.2%. These results show that our method involving the use of these plasmids as RMs is reliable and practical for quantitation of GM maize and GM soy.

Base Sequence↗

PubMed2003

Detection of genetically modified maize DNA fragments in the intestinal contents of pigs fed StarLink CBH351.

We tried to detect DNA fragments derived from maize in the intestinal contents of pigs fed genetically modified (GM) StarLink CBH351 maize (SL) or non-GM maize. Intestinal contents of 8 SL and 8 non-GM maize-fed pigs were collected at slaughter, and the genes of the recombinant cry9C and the maize intrinsic zein (Zel) were assayed by polymerase chain reaction (PCR) 3 times with a total of 4 primer pairs of different expected lengths. The cry9C gene (either 103 or 170 bp) was detected in the rectal contents (with a frequency of 25-37.5%) and in the cecal contents (25-50%) of the pigs fed SL. In a similar fashion, the zein (Zel) gene (either 242 or 329 bp) was detected in the rectal contents (with a frequency of 31.3%) and in the cecal contents (25-37.5%) of pigs fed on SL non-GM maize. These results suggested that ingested DNA was not totally degraded, but is present in a form detectable by PCR.

Animal Feed↗

PubMed2003

Expressions of human p53 and c-myc gene homologues during caryopsis development in maize.

Tumor suppressor gene p53 and proto-oncogene c-myc have been proved to be highly conserved and participate in many PCD processes in animals. In maize, proteins and RNAs related to p53 and c-myc have already been reported and the sequences homologous to these two genes have also been localized onto maize chromosomes by FISH. In this study, using immunohistochemistry we investigated the expression patterns of maize genes homologous to human p53 and c-myc during caryopsis development stages in maize. In a giving stage after pollination, p53 homologue showed high levels in the antipodal cells, integument, immature endosperm, ovary wall, tracheary elements, and aleurone layer, while c-myc homologue showed low levels in these tissues, only before pollination showed high expression in polar nucleus. The results of TUNEL assay demonstrated that TUNEL positive signals were detected where p53 homologue showed high expression levels. In animal cells, p53 shows reverse function with that of c-myc, so does it in maize basically. These results demonstrated that p53 and c-myc homologues might play some important roles in PCD during caryopsis development in maize. There may be conserved mechanisms for PCD in animals and in high plants.

Apoptosis↗