Biochemical composition of maize (Zea mays L.) pollen

Summary Pollen grains containing either the Wx, wx, Su ₁, su ₁, Sh ₂ or sh ₂ alleles were stored at 0, 1, 2, 3, 4 and 5 days at 2 °C. After each storage period, a portion of pollen from each genotype was analyzed for free amino acid content. Over all genotypes, storage significantly altered the content of all 16 amino acids measured. With increasing storage, a relatively consistent increase in aspartic acid, isoleucine, leucine, phenylalanine, ethanolanine, aminobutyric acid, NH₃ and lysine was found. A relatively consistent decrease in glutamic acid, proline, glycine and alanine occurred with increasing storage. No consistent response to storage was obtained with threonine-serine, valine, histidine and the unknown. Apparently, storage or stage of viability loss has a pronounced effect on amino acid metabolism in maize pollen grains. The experiment was designed so that comparisons free of genetic background effects could be made between alleles at each locus. Significant allele X storage interactions at each locus were found as follows: at the waxy locus, aspartic acid, glycine, alanine and ethanolanine; at the sugary locus, aspartic acid, alanine, ethanolanine and aminobutyric acid; and at the shrunken locus, aspartic acid, alanine, valine, leucine and ethanolanine. Amino acid metabolism is apparently influenced by the action of the alleles at these loci. The differences between the loci in the amino acids affected indicate the different areas of amino acid metabolism are influenced by each locus.Journal Series Paper No. 4425, Florida Agricultural Experiment Station.     

Biochemical composition of maize (Zea mays L.) pollen

Summary Mean percentages of sugars, water-soluble polysaccharides, starch, total carbohydrates and lipids were 40.1, 7.4, 28.6, 76.1, and 1.8 respectively. Differences among the mutants were found only for water-soluble polysaccharides with both wx and sh ₂ decreasing the percentage a small but significant amount. In terms of the various carbohydrates measured, no correlation was found between the expression of these mutants in the pollen and the kernel.

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Zusammenfassung Die Untersuchung des Kohlenhydrat- und Lipid-Gehaltes im Pollen der Endosperm-Mutanten waxy, shrunken und sugary vom Mais ergab einen gemittelten Gehalt an Zucker von 40,1%, wasserlöslichen Polysacchariden 7,4%, Stärke 28,6, Gesamtkohlenhydraten 76,1% und Lipiden 1,8%.Unterschiede zwischen den Mutanten wurden lediglich hinsichtlich der wasserlöslichen Polysaccharide gefunden, und zwar bei wx und sh ₂, die einen signifikant niedrigeren Gehalt aufwiesen.Hinsichtlich der verschiedenen analysierten Kohlenhydrate wurde keine Korrelation zwischen der Expression der Mutanten im Pollen und in den Karyopsen gefunden.

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Herrn Professor Dr. J. Straub (Köln-Vogelsang) zu seinem 60. Geburtstag gewidmet.

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Journal Series Paper No. 3621, Florida Agricultural Experiment Station.     

Biochemical composition of maize (Zea mays L.) pollen

Summary Proline was the most abundant amino acid with a mean value of 186.28 moles/mg dry pollen. The other amino acids tested were below 33 moles/mg dry pollen. The mutant wx significantly increased aspartic acid, valine, histidine and an unknown but significantly decreased aminobutyric acid. The mutant sh ₂ significantly increased glutamic acid, proline, lysine, histidine and an unknown but significantly decreased aspartic acid and aminobutyric acid. The effect of su ₁ was altered by the genetic background involved. In one genetic background, su ₁ did not significantly increase any amino acid but significantly decreased alanine and aminobutyric acid. However, in a distinctly different background, su ₁ significantly increased aminobutyric acid but significantly decreased aspartic acid and glutamic acid. Apparently the genetic background is capable of producing major shifts in the amino acid pattern in addition to the action of these mutants.The fatty acids, palmitic and linolenic were the most common with percentages of 54.1 and 34.4 respectively. The mutants tested did not affect the fatty acid distribution.

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Zusammenfassung Prolin war die am reichlichsten vorkommende Aminosäure mit einem mittleren Gehalt von 186,28 Mikromol per mg trockenen Pollen. Die anderen Aminosäuren erreichten weniger als 33 Mikrogramm per mg trockenen Pollen.Die Mutante wx zeigte einen signifikant erhöhten Gehalt an Asparaginsäure, Valin, Histidin, sowie einer nicht identifizierten Komponente, während der Gehalt an -Aminobuttersäure signifikant erniedrigt war. Die Mutante sh ₂ ist gekennzeichnet durch einen signifikant erhöhten Gehalt an Glutaminsäure, Prolin, Lysin, Histidin, sowie einer unbekannten Fraktion; der Gehalt an Asparaginsäure und -Aminobuttersäure war dagegen signifikant erniedrigt. Die Wirkung des mutierten Gens su ₁ wurde durch das übrige Genom, in dem es sich befand, geändert. In dem einen genetischen Milieu verursachte su ₁ keine signifikante Erhöhung des Gehaltes irgend einer Aminosäure, während der Gehalt an Alanin und -Aminobuttersäure signifikant erniedrigt war. In einem anderen genetischen Milieu jedoch zeigte su ₁ eine signifikante Erhöhung der -Aminobuttersäure; Asparaginsäure und Glutaminsäure waren signifikant erniedrigt.Offensichtlich ist das übrige Genom zusätzlich zu der Wirkung der genannten Mutanten in der Lage, wesentliche Verschiebungen im Verteilungsmuster der Aminosäuren zu verursachen.Von den Fettsäuren wurden am häufigsten Palmitin- und Linolen-Säure mit einem Gehalt von 54,1 bzw. 34,4% gefunden. Die untersuchten Endosperm-Mutanten zeigten keinen Einfluß auf die Fettsäureverteilung im Pollen.

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Journal Series Paper No. 3468, Florida Agricultural Experiment Station.     

Ameliorative role of zinc on maize growth (Zea mays L.) under salt-affected soil conditions

A greenhouse experiment, growing maize for six weeks, was conducted to evaluate the ameliorative role of Zn (0 and 10 ppm Zn) under saline (ECe4, 8 and 12 mmhos/cm), Sodic (ESP 10, 20 and 30) and saline-sodic (all possible combinations of above salinity and sodicity levels), and normal soil conditions using a sandy loam (Typic Ustochrepts) soil sample.Zinc ameliorated plant growth under salt-affected soil conditions. Ameliorative effect was more under sodic than under saline or saline-sodic soil conditions. Shoot yield decreased with Salinity level of 12 mmhos/cm, and ESP 30 and adverse effects were accentuated with increasing level of ESP and Salinity, respectively.Shoot Zn increased with applied Zn. Increasing sodicity in soil under Zn deficient or low salinity conditions generally decreased shoot Zn, whereas the low level of soil salinization counteracted the adverse effect of high sodicity. Shoot Na increased but K decreased with increasing sodicity and salinity in soil. Shoot Na decreased but K increased with applied Zn. Shoot Ca increased with salinity levels of 4 and 8 mmhos/cm, but decreased with 12 mmhos/cm at 0 Zn level. Sodicity decreased shoot Ca, whereas Zn counteracted adverse effect of high sodicity. Shoot Mg generally increased with increasing salinity, but decreased with increasing sodicity. Zinc had no definite effect. Shoot Ca/Na and K/Na ratios were widened with Zn and narrowed down with high ESP.The effects of salinity, sodicity, and Zn on plant growth and its composition were generally associated with their respective roles in dry matter production, and inter-ionic relationships among Ca, Mg, K, Na and Zn in soils and plants.Contribution from the Department of Soils, Haryana Agricultural University, Hissar, 125004, Indiaformer Research Fellow, respectively.     

Effect of soil application of chlorinated insecticides on amino acid composition of maize (Zea mays)

Summary Chlorinated insecticidesviz p,p-DDT, aldrin, endrin and lindane stimulated the synthesis of arginine+histidine, leucine, lysine, proline, and tyrosine in maize but decreased the content of tryptophan. However, synthesis of methionine was stimulated by the application of aldrin, endrin, and lindane only. On the otherhand, synthesis of valine was inhibited by aldrin, endrin and DDT only.     

Zinc deficiency and pollen fertility in maize (Zea mays)

Zinc deficiency decreased pollen viability in maize (Zea mays L. cv. G2) grown in sand culture. On restoring normal zinc supply to zinc-deficient plants before the pollen mother cell stage of anther development, the vegetative yield of plants and pollen fertility could be recovered to a large extent, but the recovery treatment was not effective when given after the release of microspores from the tetrads. If zinc deficiency was induced prior to microsporogenesis it did not significantly affect vegetative yield and ovule fertility, but decreased the fertility of pollen grains, even of those which visibly appeared normal. If the deficiency was induced after the release of microspores from the tetrads, not only vegetative yield and ovule fertility but pollen fertility also remained unaffected.     

Genome-wide analysis of primary auxin-responsive Aux/IAA gene family in maize (Zea mays. L.)

The phytohormone auxin is important in various aspects of organism growth and development. Aux/IAA genes encoding short-lived nuclear proteins are responsive primarily to auxin induction. Despite their physiological importance, systematic analysis of Aux/IAA genes in maize have not yet been reported. In this paper, we presented the isolation and characterization of maize Aux/IAA genes in whole-genome scale. A total of 31 maize Aux/IAA genes (ZmIAA1 to ZmIAA31) were identified. ZmIAA genes are distributed in all the maize chromosomes except chromosome 2. Aux/IAA genes expand in the maize genome partly due to tandem and segmental duplication events. Multiple alignment and motif display results revealed major maize Aux/IAA proteins share all the four conserved domains. Phylogenetic analysis indicated Aux/IAA family can be divided into seven subfamilies. Putative cis-acting regulatory DNA elements involved in auxin response, light signaling transduction and abiotic stress adaption were observed in the promoters of ZmIAA genes. Expression data mining suggested maize Aux/IAA genes have temporal and spatial expression pattern. Collectively, these results will provide molecular insights into the auxin metabolism, transport and signaling research.     

Effects of some mineral nutrients on gibberellic acid levels in maize plants (Zea mays L.)

The effects of different concentrations of various macroelements on growth and endogenous GAs levels in root, stem, and leaf tissue of maize plants (Zea mays L.) were studied. Plants were cultivated in sand and supplied twice a week with a nutrient solution containing optimum, excessive, or deficient concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and iron. Plants were harvested from three different periods: vegetation (4–5 leaves), flowering, and fruiting. The levels of gibberellic acid-like substances (GA₃ equivalents ng g^-1 FW) were determined by using high-performance liquid chromatography (HPLC). In the first period (vegetative; 4–5 leaves), the levels of GAs in root, stem, and leaf of maize plants treated with excessive concentration of N, P, and Mg were increased between 6% and 27%. In the second period (flowering), significant increase was not observed in the levels of GAs, whereas a decrease was determined between 8% and 35%. In the third period (fruiting), the levels of GAs were lower (between 11% and 76%) than control plants in all applications.     

The response of maize (Zea mays) to Azospirillum inoculation in various types of soils in the field

Application of a peat-based powder inoculant of Azospirillum brasilense, as well as a granular inoculant (each containing 0.5–1.0×10⁷ Azospirillum/g moist peat), in the seed furrows of Zea mays resulted in significantly increased yields (11 to 14%) in light soils at low rates of N fertilization. In general, there was no effect of inoculation on plant yields in heavier soils nor when N fertilization was high. Pre-emergence application of granular inoculant and inoculation associated with irrigation were more efficient in increasing yield than inoculation post-emergence or seed coating.E. Fallik is with ARO-The Volcani Centre, Department of Postharvest Science of Fresh Produce, Bet-Dagan 50250, Israel. Y. Okon is with The Hebrew University of Jerusalem, Faculty of Agriculture, Department of Plant Pathology and Microbiology, Rehovot 76100, Israel     

Modeling the tertiary structure of a maize (Zea mays ssp. mays) non-symbiotic hemoglobin.

The tertiary structure of a maize (Zea mays ssp. mays) non-symbiotic hemoglobin (Hbm) was modeled using computer tools and the known tertiary structure of rice Hb1 as a template. This method was tested by predicting the tertiary structure of soybean leghemoglobin a (Lba) using rice Hb1 as a template. The tertiary structures of the predicted and native Lba were similar, indicating that our computer methods could reliably predict the tertiary structures of plant Hbs. We next predicted the tertiary structure of Hbm. Hbm appears to have a long pre-helix A and a large CD-loop. The positions of the distal and proximal His are identical in Hbm and rice Hb1, which suggests that heme-Fe is hexacoordinate in Hbm and that the kinetic properties of Hbm and rice Hb1 are expected to be very similar, i.e. that Hbm has a high O2-affinity. Thermostability analysis showed that Hbm CD-loop is unstable and may provide mobility to amino acids located at the heme pocket for both ligand binding and stabilization and heme-Fe coordination. Analysis of the C-terminal half of Hbm showed the existence of a pocket-like region (the N/C cavity) where interactions with organic molecules or proteins could be possible. Lys K94 protrudes into the N/C cavity, suggesting that K94 may sense the binding of molecules to the N/C cavity. Thus, it is likely that the instability of the CD-loop and the possibility of binding molecules to the N/C cavity are essential for positioning amino acids in the heme pocket and in regulating Hbm activity and function.     

Expression profile of maize (Zea mays) scutellar epithelium during imbibition

The scutellum is a shield-shaped structure surrounding the embryo axis in grass species. The scutellar epithelium (Sep) is a monolayer of cells in contact with the endosperm. The Sep plays an important role during seed germination in the secretion of gibberellins and hydrolytic enzymes and in the transport of the hydrolized products to the growing embryo. We identified 30 genes predominantly expressed after imbibition in the Sep as compared to other parts of the scutellum. A high proportion of these genes is involved in metabolic processes. Some other identified genes are involved in the synthesis or modification of cell walls, which may be reflected in the changes of cell shape and cell wall composition that can be observed during imbibition. One of the genes encodes a proteinase that belongs to a proteinase family typical of carnivorous plants. Almost nothing is known about their role in other plants or organs, but the scutellar presence may point to a "digestive" function during germination. Genes involved in the production of energy and the transport of peptides were also identified.     

Free and conjugated desmethylsterol composition of Zea mays hybrids exposed to mild osmotic stress

Five hybrids of Zea mays (A619 × H60, B73 × MO17, B73 × PA91, B73 × VA17. A632 × H96) were grown hydroponically at osmotic potentials of -0.1 (control), -0.4 and -0.6 MPa. Dry weights of hybrids B73 × VA17 and A632 × H96 decreased significantly at -0.4 and -0.6 MPa. Few changes were observed in the free sterol, steryl glycoside and steryl ester fractions. However, steryl esters of the roots and stems of osmotically treated plants declined in most of the hybrids. The stigmasterol to sitosterol ratio increased in all three steryl fractions in the roots of B73×VA17 and A632×H96 as a result of the osmotic treatments. B73×VA17 and A632×H96 also exhibited the greatest initial electrolyte leakage when leaf dises were subjected to osmotic stress. A632×H96 and possibly B73×VA17 were less tolerant to osmotic treatments than the other hybrids. Modification of sterols may reflect initial events that lead to the stabilization or destabilization of cellular membrances which in turn may affect the tolerance of plants to stressful environments.     

Phytoliths as indicators of prehistoric maize (Zea mays subsp.mays,Poaceae) cultivation

Maize (Zea mays L. subsp.mays) has been identified in archaeological contexts by a high proportion of large cross-shaped phytoliths. Given the numerous races of maize, this study was undertaken to determine if differences below the species level could be noted. It was also designed to see if phytoliths differed in various plant parts at various stages of growth. Several races were grown under experimental conditions. No significant differences were found. Furthermore, few phytoliths alleged to be diagnostic of maize were discovered. Systemic studies of maize and analyses of prehistoric cultivation by means of phytoliths seem not to be as promising as some researchers have argued.     

Role of growth regulators in differentiation processes of maize (Zea mays L.) organs

The following paper deals with the character of endogenous auxins and gibberellinlike substances in the maize tassel and ear primordia during differentiation. Using bioassay the character of substances extracted from tassel primordia, internodes below the tassel, ear primordia and stem base was determined and correlated with the course of morphogenesis and differentiation. A low level of auxins and a high content of gibberellin-like substances accompanies the differentiation of terminal tassel. The differentiation of an ear is associated with an increment in auxin content while the level of gibberellin-like substances decreases. The character of growth substances in primordia remains practically unchanged in the course of further differentiation. The inhibitions appear in the plant and probably start numerous morphological reductions in the pistillate inflorescence structure or inhibit the growth of lateral primordia on the stemetc. The treatment of plants with maleic hydrazide at the beginning of tassel differentiation shifts the normal levels of endogenous regulators and brings about the transformation of tassel primordia into an ear. This transformation is accompanied by a marked rise in gibberellin-like substances, by an increment in auxins and the appearance of inhibitors.     

Distribution of the glutamine synthetase isozyme GSp1 in maize (Zea mays)

In maize (Zea mays L.), GSp1, the predominant GS isozyme of the developing kernel, is abundant in the pedicel and pericarp, but absent from the endosperm and embryo. Determinations of GSp1 tissue distribution in vegetative tissues have been limited thus far to root and leaves, where the isozyme is absent. However, the promoter from the gene encoding GSp1 has been shown to drive reporter gene expression not only in the maternal seed-associated tissues in transgenic maize plants, but also in the anthers, husks and pollen (Muhitch et al. 2002, Plant Sci 163: 865-872). Here we report chromatographic evidence that GSp1 resides in immature tassels, dehiscing anthers, kernel glumes, ear husks, cobs and stalks of maize plants, but not in mature, shedding pollen grains. RNA blot analysis confirmed these biochemical data. In stalks, GSp1 increased in the later stages of ear development, suggesting that it plays a role in nitrogen remobilization during grain fill.     

Improving the mineral reserves and protein quality of maize (Zea mays L.) kernels using unique genes

The effects of the maize genes, o ₂ and Mal, on the concentrations of mineral nutrient cations and amino acid levels in mature maize (Zea mays L) kernels of various inbred lines were studied. Previously, the o ₂ gene has been used to improve the protein quality and increase the mineral nutrient content of kernels from some inbred lines. Genotypes possessing the Mal (multiple aleurone layer) gene, contain more than one row of aleurone cells in their kernels and this gene enhances the effect of the o ₂gene on improving kernel protein quality. Incorporating these genes into the maize genome increased accumulation of several mineral nutrients (including Ca, Mg, Zn, Fe, Mn, Zn and Cu) in some of the experimental lines studied. The physiological basis for this increase of mineral nutrients in the kernels is discussed. The effect of the Mal gene on the kernel amino acid composition and protein quality was also examined. Possibly, these genes could be used in combination in breeding programs to improve kernel quality and nutritional value of maize.     

Plant defense against fall armyworm in micro‐sympatric maize (Zea mays ssp. mays) and Balsas teosinte (Zea mays ssp. parviglumis)

Maize [Zea mays L. ssp. mays (Poaceae)] was domesticated from Balsas teosinte (Zea mays ssp. parviglumis Iltis & Doebley) in present‐day Mexico. Fall armyworm, Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), is among the most important pests of maize in Mexico and Central America. We compared the strength of plant defenses against fall armyworm between micro‐sympatric landrace maize and Balsas teosinte in the field and laboratory. The field comparison, conducted in Mexico, consisted of comparing the frequency of fall armyworm infestation between young maize and Balsas teosinte plants in dryland agricultural fields in which Balsas teosinte grew as a weed. The laboratory comparison contrasted the performance of fall armyworm larvae provided a diet of leaf tissue excised from maize or Balsas teosinte plants that were intact or had been primed by larval feeding. In the field, maize plants were more frequently infested with fall armyworm than Balsas teosinte plants: over 3 years and three fields, maize was infested at a ca. 1.8‐fold greater rate than Balsas teosinte. In the laboratory, larval growth, but not survivorship, was differently affected by feeding on maize vs. Balsas teosinte, and on primed vs. intact plants. Specifically, survivorship was ca. 98%, and did not differ between maize and Balsas teosinte, nor between primed and intact plants. Larvae grew less on intact vs. primed maize, and similarly on intact vs. primed Balsas teosinte; overall, growth was 1.2‐fold greater on maize compared to Balsas teosinte, and on primed compared to intact plants. Parallel observations showed that the differences in growth could not be attributed to the amount of leaf tissue consumed by larvae. We discuss our results in relation to differences in the strength of plant defenses between crops and their ancestors, the relevance of unmanaged Balsas teosinte introgression in the context of fall armyworm defenses in maize, and whether greater growth of larvae on primed vs. intact plants signifies herbivore offense.