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PubMed1990

Maize and risk of cancers of the oral cavity, pharynx, and esophagus in northeastern Italy.

The relationship between maize consumption and risk of cancer of the upper digestive tract was investigated in 107 patients with oral cancer, 107 with pharyngeal cancer, 68 with esophageal cancer, and 505 hospital controls who permanently resided in Pordenone Province in the northeastern part of Italy. The analysis was restricted to males. The population of this province has a high incidence of these neoplasms and shows particularly elevated levels of alcohol and tobacco use, in addition to high maize consumption. Highly significant associations with frequent intake of maize emerged for oral cancer, pharyngeal cancer, and esophageal cancer (odds ratios = 3.3, 3.2, and 2.8, respectively). The risk elevation could not be explained in terms of differences in education, occupation, tobacco use, or consumption of fresh fruits and vegetables. The unfavorable effect of maize on risk of cancer of the upper digestive tract, however, was evident only in those individuals who reported heavy drinking (i.e., greater than or equal to 42 alcoholic drinks/wk). The present findings are likely to be related to the fact that maize can cause deficiencies of various micronutrients (chiefly, niacin and riboflavin) and agree with previous observations from Africa, the People's Republic of China, the United States, and Italy.

Adult↗

PubMed2003

Induction of nitrate uptake in maize roots: expression of a putative high-affinity nitrate transporter and plasma membrane H+-ATPase isoforms.

An investigation was carried out to assess the effect of nitrate supply on the root plasma membrane (PM) H+-ATPase of etiolated maize (Zea mays L.) seedlings grown in hydroponics. The treatment induced higher uptake rates of the anion and the expression of a putative high-affinity nitrate transporter gene (ZmNRT2.1), the first to be identified in maize. Root PM H+-ATPase activity displayed a similar time-course pattern as that of net nitrate uptake and investigations were carried out to determine which of the two isoforms reported to date in maize, MHA1 and 2, responded to the treatment. MHA1 was not expressed under the conditions analysed. Genome analysis revealed that MHA2, described as the most abundant form in all maize tissues, was not present in the maize hybrid investigated, but a similar form was found instead and named MHA3. A second gene (named MHA4) was also identified and partially sequenced. Both genes, classified as members of the PM H+-ATPase subfamily II, responded to nitrate supply, although to different degrees: MHA4, in particular, proved more sensitive than MHA3, with a greater up- and down-regulation in response to the treatment. Increased expression of subfamily II genes resulted in higher steady-state levels of the enzyme in the root tissues and enhanced ATP-hydrolysing activity. The results support the idea that greater proton-pumping activity is required when nitrate inflow increases and suggest that nitrate may be the signal triggering the expression of the two members of PM H+-ATPase subfamily II.

Amino Acid Sequence↗

PubMed2006

Characterization of five microRNA families in maize.

In recent years, microRNAs (miRNAs) have polarized the interest of the scientific community as a new category of gene expression regulators, present in both plants and animals. Plant miRNAs are involved in processes such as plant development, organ identity, and stress response. Nonetheless, knowledge of their functions is still incomplete, and it is conceivable that further new processes in which they are involved will be discovered. For these reasons, structural and functional characterization of MIR genes, that are also in crop species such as Zea mays L., becomes instrumental in addressing genetic and molecular mechanisms controlling phenotype determination and phenotypic adaptation to growing conditions. The present study contributes to the characterization of five miRNA families in maize, from the determination of their expression pattern in different maize tissues and genotypes, to the identification of putative targets by bioinformatic means and subsequent experimental validation of three targets by modified 5' RACE experiments. Furthermore, 30 different MIR genes belonging to these five miRNA families were analysed by their attribution to maize chromosomes using oat-maize addition lines and by investigating their phylogenetic relationship with genes from other cereals. In particular, sequence homology was determined by the reciprocal best BLAST hit approach, to define groups of homologous genes between maize, rice, and sorghum.

Chromosome Mapping↗

PubMed2003

Directional evolution for microsatellite size in maize.

Directional evolution in microsatellites is the tendency for microsatellites either to increase or to decrease in size over time between populations. We analyzed 99 microsatellite loci in a sample of 193 maize plants representing the entire pre-Columbian range of this crop for evidence of directional evolution. We took advantage of the known phylogeographic history of maize with the independent movement of maize from its ancestral location in Mexico to North and South America. We show that there is an increase in the average allele size of microsatellites in the geographically derived North and South American groups relative to the ancestral Mexican group. We also show that there is a negative correlation between average allele size and altitude in all three groups. Directional evolution in maize microsatellites can be explained by changes in the mutation rate over time and space, changes in the degree of mutational bias to a larger allele, demographic differences between the ancestral and geographically derived populations, and/or scenarios involving selection on microsatellite size. The occurrence of directional evolution for microsatellite size indicates that the estimation of population parameters with microsatellite data in maize should be done with caution.

Alleles↗

PubMed1989

Diversity of 7 SL RNA from the signal recognition particle of maize endosperm.

An 11 S ribonucleoprotein particle was isolated from maize endosperm and shown to be functionally and structurally equivalent to the mammalian signal recognition particle. However, unlike animal cells which apparently contain a single 7 SL RNA species, maize endosperm contains a heterogeneous population of 7 SL RNA. To investigate this diversity, we have cloned and sequenced a number of the maize endosperm 7 SL RNAs isolated from functionally active SRP preparations. Some maize 7 SL RNAs are strikingly similar, differing by single base changes or short deletions; surprisingly, others share less than 70 percent sequence homology. Despite differences in primary sequence, nearly identical secondary structures can be suggested for all maize 7 SL RNAs, consistent with a proposed functional role in protein translocation for each of these RNAs. The amount of new available sequence data enabled us to define two conserved regions of presumed functional importance: A conserved sequence -G-N-A-R- in the center of a variable region which forms a well defined stem-loop and possibly is involved in an interaction with the 19 kDa protein of the SRP. Secondly, three short nucleotide stretches located in the central domain of 7 SL RNA may form part of a dynamic RNA-switch structure.

Base Sequence↗

PubMed1991

Maize chloroplast RNA polymerase: the 78-kilodalton polypeptide is encoded by the plastid rpoC1 gene.

The 180-, 120- and 38-kDa polypeptides found in highly purified maize plastid RNA polymerase preparations are encoded by the maize plastid genes rpoC2, rpoB, and rpoA, respectively [Hu, J. and Bogorad, L. (1990) Proc. Natl. Acad. Sci. USA. 87, pp. 1531-1535]. These genes have segments that specify amino acid sequences homologous to those of E. coli RNA polymerase subunits. The plastid gene products are designated b", b and a, respectively. We report here that the amino-terminal amino acid sequence of a 78-kDa polypeptide also found in highly purified maize plastid RNA polymerase preparations matches precisely the sequence deduced from the maize plastid rpoC1 gene which has segments homologous to the 5' end of the E. coli rpoC gene. Thus, the 78-kDa polypeptide is likely to be a functional component of maize plastid DNA-dependent RNA polymerase. This polypeptide is designated subunit b'. Three polypeptides unrelated to RNA polymerase have also been identified in this preparation.

Amino Acid Sequence↗

PubMed1995

ZEMa, a member of a novel group of MADS box genes, is alternatively spliced in maize endosperm.

The identification of a number of cis-elements which direct gene expression in maize endosperm, and the characterization of corresponding DNA binding proteins, point to the interaction of different classes of transcription factors in this tissue. To assess whether MADS box genes are also involved in maize endosperm development, cDNA and genomic MADS box clones have been isolated. The three cDNA clones ZEM1, ZEM2 and ZEM3 were cloned from a maize endosperm cDNA library using a probe based on sequences conserved in plant MADS box genes. Further transcripts were cloned by RT-PCR experiments and designated ZEM4 and ZEM5. Analysis of the corresponding genomic clones led to the identification of the ZEM2 MADS box gene family, three members of which were characterized sharing 97% sequence identity in corresponding domains. 100% sequence identities between cDNA and one of the genomic clones, conserved exon-intron boundaries and the demonstration of in vivo splicing in a maize endosperm transient expression system, show that the transcripts ZEM1-5 are derived by alternative splicing of ZEMa, one ZEM2 member. The ZEMa transcripts are present in almost all maize tissues, but specific differentially spliced forms accumulate preferentially in maturing endosperm and leaf. The function of the ZEMa gene is discussed in the light of similarities in the expression pattern with members of the human MEF2/RSRF gene family.

Alternative Splicing↗

PubMed2004

Asymmetric localization of seed storage protein RNAs to distinct subdomains of the endoplasmic reticulum in developing maize endosperm cells.

Plant storage proteins are synthesized and stored in different compartments of the plant endomembrane system. Developing maize seeds synthesize and accumulate prolamin (zein) and 11S globulin (legumin-1) type proteins, which are sequestered in the endoplasmic reticulum (ER) lumen and storage vacuoles, respectively. Immunofluorescence studies showed that the lumenal chaperone BiP was not randomly distributed within the ER in developing maize endosperm but concentrated within the zein-containing protein bodies. Analysis of the spatial distribution of RNAs in maize endosperm sections by in situ RT-PCR showed that, contrary to the conclusions made in an earlier study [Kim et al. (2002) Plant Cell 14: 655-672], the zein and legumin-1 RNAs are not symmetrically distributed on the ER but, instead, targeted to specific ER subdomains. RNAs coding for 22 kDa alpha-zein, 15 kDa beta-zein, 27 kDa gamma-zein and 10 kDa delta-zein were localized to ER-bounded zein protein bodies, whereas 51 kDa legumin-1 RNAs were distributed on adjacent cisternal ER proximal to the zein protein bodies. These results indicate that the maize storage protein RNAs are targeted to specific ER subdomains in developing maize endosperm and that RNA localization may be a prevalent mechanism to sort proteins within plant cells.

Endoplasmic Reticulum↗

PubMed2006

Abscisic acid is a key inducer of hydrogen peroxide production in leaves of maize plants exposed to water stress.

The histochemical and cytochemical localization of water stress-induced H(2)O(2) production in the leaves of ABA-deficient vp5 mutant and wild-type maize (Zea mays L.) plants were examined, using 3,3-diaminobenzidine and CeCl(3) staining, respectively, and the roles of endogenous ABA in the production of H(2)O(2) induced by water stress were assessed. Water stress induced by polyethylene glycol resulted in the accumulation of H(2)O(2) in mesophyll cells, bundle-sheath cells and vascular bundles of wild-type maize leaves, and the accumulation was substantially blocked in the mutant maize leaves exposed to water stress. Pre-treatments with several apoplastic H(2)O(2) manipulators abolished the majority of H(2)O(2) accumulation induced by water stress in the wild-type leaves. The subcellular localization of H(2)O(2) production was demonstrated in the cell walls, xylem vessels, chloroplasts, mitochondria and peroxisomes in the leaves of wild-type maize plants exposed to water stress, and the accumulation of H(2)O(2) induced by water stress in the cell walls and xylem vessels, but not in the chloroplasts, mitochondria and peroxisomes, was arrested in the leaves of the ABA mutant or the ABA biosynthesis inhibitor (tungstate)-pre-treated maize plants. Pre-treatments with the apoplastic H(2)O(2) manipulators also blocked the apoplastic but not the intracellular H(2)O(2) accumulation induced by water stress in the leaves of wild-type plants. These data indicate that under water stress, the apoplast is the major source of H(2)O(2) production and ABA is a key inducer of apoplastic H(2)O(2) production. These data also suggest that H(2)O(2) generated in the apoplast could not diffuse freely into subcellular compartments.

Abscisic Acid↗

PubMed2024

A maize semi-dwarf mutant reveals a GRAS transcription factor involved in brassinosteroid signaling.

Brassinosteroids (BR) and gibberellins (GA) regulate plant height and leaf angle in maize (Zea mays). Mutants with defects in BR or GA biosynthesis or signaling identify components of these pathways and enhance our knowledge about plant growth and development. In this study, we characterized three recessive mutant alleles of GRAS transcription factor 42 (gras42) in maize, a GRAS transcription factor gene orthologous to the DWARF AND LOW TILLERING (DLT) gene of rice (Oryza sativa). These maize mutants exhibited semi-dwarf stature, shorter and wider leaves, and more upright leaf angle. Transcriptome analysis revealed a role for GRAS42 as a determinant of BR signaling. Analysis of the expression consequences from loss of GRAS42 in the gras42-mu1021149 mutant indicated a weak loss of BR signaling in the mutant, consistent with its previously demonstrated role in BR signaling in rice. Loss of BR signaling was also evident by the enhancement of weak BR biosynthetic mutant alleles in double mutants of nana plant1-1 and gras42-mu1021149. The gras42-mu1021149 mutant had little effect on GA-regulated gene expression, suggesting that GRAS42 is not a regulator of core GA signaling genes in maize. Single-cell expression data identified gras42 expressed among cells in the G2/M phase of the cell cycle consistent with its previously demonstrated role in cell cycle gene expression in Arabidopsis (Arabidopsis thaliana). Cis-acting natural variation controlling GRAS42 transcript accumulation was identified by expression genome-wide association study (eGWAS) in maize. Our results demonstrate a conserved role for GRAS42/SCARECROW-LIKE 28 (SCL28)/DLT in BR signaling, clarify the role of this gene in GA signaling, and suggest mechanisms of tillering and leaf angle control by BR.

Zea mays↗

PubMed2004

Toxicity of maize containing known levels of fumonisin B1 during force-feeding of ducks.

The toxicity of maize containing known doses of fumonisin B1 (FB1) was investigated in mallard ducks during force-feeding. Seventy-five ducks at 12 wk of age were randomly divided into 3 groups of 25, and received control maize, naturally contaminated maize containing 20 mg/kg of FB1, or a mixture of control and contaminated maize (50/50, vol/vol). Force-feeding was performed during 12 d that correspond to a final average feed intake of approximately 10 kg of maize per duck. At the end of the study, 8% mortality was observed in ducks fed 20 mg of FB1/kg of feed, whereas no mortality occurred in the other groups. Liver weight, and plasma concentrations of protein, cholesterol, alanine aminotransferase (ALAT), and lactate dehydrogenase (LDH) were increased by force-feeding, whereas feed conversion ratio appeared decreased by the toxin. Microscopic examination of the liver showed that steatosis was mostly macrovacuolar in control ducks, whereas it was microvacuolar in ducks fed 20 mg of FB1/kg of feed. Free sphingolipid concentrations were measured in liver and plasma. Sphinganine (Sa) and sphinganine to sphingosine (Sa/So) ratio were increased in all treatment groups. These parameters were not affected by force-feeding and all individual values obtained in the treated ducks were higher than those obtained in control ducks. Our results suggest that free Sa level and Sa/So ratio can be used to reveal exposure of ducks to FB1 at doses of 10 mg/kg or greater in feed.

Animals↗

PubMed2001

Comparison of safety of glucose oral rehydration solution and maize oral rehydration therapy for home management of diarrhoea in Kenya.

Safety margins and variability in the composition of glucose and maize-based oral rehydration therapy (ORT) prepared by mothers in a rural district of Western Kenya, are reported here. In a 2-year longitudinal field study, packets containing glucose ORS and a home solution made with maize and table salts, were provided to the mothers of 6180 children in Kakamega District in two separate sub-locations. Experienced and trained field workers supported by community registered nurses provided training for the preparation and use of ORT during weekly visits to every household. On four occasions separated by 4-6 months, a 5 per cent random sampling was done of the home-prepared solutions actually used for the treatment of children with diarrhoea. The water used for preparing ORT was also sampled. Samples of 174 glucose-based ORT, 148 maize-salt ORT, and 201 samples of water were analysed. Only 2 per cent of the maize-based ORT were above 120 meq/1 sodium (i.e., the safe range of sodium concentration) compared to 17.8 per cent for glucose solutions (p < 0.001). Home water samples contained substantial amounts of salt, which could unpredictably affect the final composition of the ORT solutions. We conclude that maize-salt ORT had a better margin of safety than glucose-based ORS.

Child, Preschool↗

PubMed1997

Discrete regions of the sensor protein virA determine the strain-specific ability of Agrobacterium to agroinfect maize.

The ability of Agrobacterium strains to infect transformation-recalcitrant maize plants has been shown to be determined mainly by the virA locus, implicating vir gene induction as the major factor influencing maize infection. In this report, we further explore the roles of vir induction-associated bacterial factors in maize infection using the technique of agroinfection. The Ti plasmid and virA source are shown to be important in determining the ability of a strain to infect maize, and the monosaccharide binding protein ChvE is absolutely required for maize agroinfection. The linker domain of VirAC58 from an agroinfection-competent strain, C58, is sufficient to convert VirAA6 of a nonagroinfecting strain, A348,to agroinfection competence. The periplasmic domain of VirAC58 is also able to confer a moderate level of agroinfection competence to VirAA6. In addition, the VirAA6 protein from A348 is agroinfection competent when removed from its cognate Ti plasmid background and placed in a pTiC58 background. The presence of a pTiA6-encoded, VirAA6-specific inhibitor is hypothesized and examined.

Amino Acid Sequence↗

PubMed1998

Induced resistance responses in maize.

Systemic acquired resistance (SAR) is a widely distributed plant defense system that confers broad-spectrum disease resistance and is accompanied by coordinate expression of the so-called SAR genes. This type of resistance and SAR gene expression can be mimicked with chemical inducers of resistance. Here, we report that chemical inducers of resistance are active in maize. Chemical induction increases resistance to downy mildew and activates expression of the maize PR-1 and PR-5 genes. These genes are also coordinately activated by pathogen infection and function as indicators of the defense reaction. Specifically, after pathogen infection, the PR-1 and PR-5 genes are induced more rapidly and more strongly in an incompatible than in a compatible interaction. In addition, we show that monocot lesion mimic plants also express these defense-related genes and that they have increased levels of salicylic acid after lesions develop, similar to pathogeninfected maize plants. The existence of chemically inducible disease resistance and PR-1 and PR-5 gene expression in maize indicates that maize is similar to dicots in many aspects of induced resistance. This reinforces the notion of an ancient plant-inducible defense pathway against pathogen attack that is shared between monocots and dicots.

Amino Acid Sequence↗

PubMed2004

The avrRxo1 gene from the rice pathogen Xanthomonas oryzae pv. oryzicola confers a nonhost defense reaction on maize with resistance gene Rxo1.

Maize lines that contain the single dominant gene Rxo1 exhibit a rapid hypersensitive response (HR) after infiltration with the rice bacterial streak pathogen Xanthomonas oryzae pv. oryzicola, but not with the rice bacterial blight pathogen X. oryzae pv. oryzae. The avirulence effector gene that corresponds to Rxo1, designated avrRxo1, was identified in an X. oryzae pv. oryzicola genomic library. When introduced into X. oryzae pv. oryzae, clones containing avrRxo1 induced an HR on maize with Rxo1, but not on maize without Rxo1. The avrRxo1 gene is 1,266 bp long and shows no significant homology to any database sequences. When expressed in an X. oryzae pv. oryzae hrpC mutant that is deficient in the type III secretion system, avrRxo1 did not elicit the HR, indicating that the avrRxo1-Rxo1 interaction is dependent on type III secretion. Transient expression of avrRxo1 in onion cells after biolistic delivery revealed that the protein product was associated with the plasma membrane. Transient expression in maize lines carrying Rxo1 resulted in cell death, suggesting that AvrRxo1 functions from inside maize cells to elicit Rxo1-dependent pathogen recognition.

Amino Acid Sequence↗

PubMed2002

Induction of glutathione synthesis and glutathione reductase activity by abiotic stresses in maize and wheat.

The effect of different abiotic stresses (extreme temperatures and osmotic stress) on the synthesis of glutathione and hydroxymethylglutathione, on the ratio of the reduced to oxidised forms of these thiols (GSH/GSSG, hmGSH/hmGSSG), and on the glutathione reductase (GR) activity was studied in maize and wheat genotypes having different sensitivity to low temperature stress. Cold treatment induced a greater increase in total glutathione (TG) content and in GR activity in tolerant genotypes of both species than in sensitive ones. The GSH/GSSG and hmGSH/hmGSSG ratios were increased by this treatment only in the frost-tolerant wheat variety. High-temperature stress increased the TG content and the GSH/GSSG ratio only in the chilling-sensitive maize genotype, but GR activity was greater after this treatment in both maize genotypes. Osmotic stress resulted in a great increase in the TG content in wheat and the GR activity in maize. The amount of total hydroxymethylglutathione increased following all stress treatments. These results indicate the involvement of these antioxidants in the stress responses of wheat and maize.

Cold Temperature↗

PubMed2004

Characterization of the maize endosperm transcriptome and its comparison to the rice genome.

The cereal endosperm is a major organ of the seed and an important component of the world's food supply. To understand the development and physiology of the endosperm of cereal seeds, we focused on the identification of genes expressed at various times during maize endosperm development. We constructed several cDNA libraries to identify full-length clones and subjected them to a twofold enrichment. A total of 23,348 high-quality sequence-reads from 5'- and 3'-ends of cDNAs were generated and assembled into a unigene set representing 5326 genes with paired sequence-reads. Additional sequencing yielded a total of 3160 (59%) completely sequenced, full-length cDNAs. From 5326 unigenes, 4139 (78%) can be aligned with 5367 predicted rice genes and by taking only the "best hit" be mapped to 3108 positions on the rice genome. The 22% unigenes not present in rice indicate a rapid change of gene content between rice and maize in only 50 million years. Differences in rice and maize gene numbers also suggest that maize has lost a large number of duplicated genes following tetraploidization. The larger number of gene copies in rice suggests that as many as 30% of its genes arose from gene amplification, which would extrapolate to a significant proportion of the estimated 44,027 candidate genes of its entire genome. Functional classification of the maize endosperm unigene set indicated that more than a fourth of the novel functionally assignable genes found in this study are involved in carbohydrate metabolism, consistent with its role as a storage organ.

DNA, Complementary↗

PubMed1992

Cytokinin Is Required to Induce the Nitrogen-Dependent Accumulation of mRNAs for Phosphoenolpyruvate Carboxylase and Carbonic Anhydrase in Detached Maize Leaves.

Previous studies with intact maize (Zea mays L.) plants indicated that phosphoenolpyruvate carboxylase (PEPC) levels are controlled by nitrogen (N) availability and that this regulation is presumably at the transcriptional level (B. Sugiharto, K. Miyata, H. Nakamoto, H. Sasakawa, T. Sugiyama [1990] Plant Physiol 92: 963-969; B. Sugiharto, T. Sugiyama [1992] Plant Physiol 98: 1403-1408). In the present study, detached maize leaves were used to investigate further the mechanism of N-dependent regulation of gene expression in C(4) plants. PEPC and carbonic anhydrase (CA) mRNA levels decreased in leaves detached from maize plants. Addition of high nitrate did not prevent this decrease. However, the addition of zeatin to solutions bathing the cut ends of the detached leaves inhibited the decrease of PEPC and CA mRNA levels. Simultaneous addition of high nitrate and zeatin to leaves detached from N-deficient maize plants caused a large and rapid increase in PEPC and CA mRNA levels. Zeatin could be replaced by benzyladenine, but not by indoleacetic acid or abscisic acid. Both CA isozymes were effected and responded in an identical manner. We conclude that detached maize leaves provide an excellent experimental system to study the mechanism(s) of N-mediated regulation of PEPC and CA gene expression. However, zeatin is an essential component of this system.

Journal Article↗