Acid growth effects in maize roots: Evidence for a link between auxin-economy and proton extrusion in the control of root growth

The role of proton excretion in the growth of apical segments of maize roots has been examined. Growth is stimulated by acidic buffers and inhibited by neutral buffers. Organic buffers such as 2[N-morpholino] ethane sulphonic acid (MES) — 2-amino-2-(hydroxymethyl)propane-1,3 diol (Tris) are more effective than phosphate buffers in inhibiting growth. Fusicoccin(FC)-induced growth is also inhibited by neutral buffers. The antiauxins 4-chlorophenoxyisobutyric acid (PCIB) and 2-(naphthylmethylthio) propionic acid (NMSP) promote growth and H⁺-excretion over short time periods; this growth is also inhibited by neutral buffers. We conclude that growth of maize roots requires proton extrusion and that regulation of root growth by indol-3yl-acetic acid (IAA) may be mediated by control of this proton extrusion.Abbreviations IAA indol-3yl-acetic acid - ABA abscisic acid - FC fusicoccin - PCIB 4-chlorophenoxy-isobutyric acid - MES 2(N-morpholino)ethane sulphonic acid - Tris 2-amino-2-(hydroxymethyl) propane-1,3-diol - NMSP 2-(naphthylmethylthio)propionic acid     

High level accumulation of α-glucan in maize kernels by expressing the <Emphasis Type="Italic">gtfD</Emphasis> gene from <Emphasis Type="Italic">Streptococcus mutans</Emphasis>

Glucosyltransferases (GTFs, EC.2.4.1.5) are bacterial enzymes that catalyze the polymerization of glucose residues from sucrose, leading to the production of high molecular weight glucan with α-1,3 /α-1,6 linkages. Such glucans, with many potential food and industrial applications, do not normally exist in higher plants. We fused a mutant form of the gtfD gene from Sreptococcus mutans with the maize (Zea mays L.) chloroplastic Brittle 1 transit peptide for amyloplast targeting. This construct, driven by the ubiquitin promoter, was introduced into maize by Agrobacterium-mediated transformation. We developed a novel HPLC-based method that enabled us differentially to distinguish transgene glucan from other endogenous polysaccharides in maize kernels. Using this method, we screened over 100 transgenic plants for the presence of GTF-produced glucan whose content varied between 0.8 and 14% of dry weight in the mature transgenic seeds. The mature transgenic plants were indistinguishable from wildtype plants in growth rate and morphology. Furthermore, starch granule size in the transgenic maize kernel was unaffected by the accumulation of the foreign polysaccharide. Mutation in Sh2, which encodes a subunit of ADP-glucose pyrophosphorylase, had no effect on glucan accumulation caused by gtfD expression. Our results indicated that high levels of novel carbohydrate polymer can be accumulated in crop plants through transgene technology.     

Characterization of the safener-induced glutathione S-transferase isoform II from maize

The safener-induced maize (Zea mays L.) glutathione S-transferase, GST II (EC 2.5.1.18) and another predominant isoform, GST I, were purified from extracts of maize roots treated with the safeners R-25788 (N,N-diallyl-2-dichloroacetamide) or R-29148 (3-dichloroace-tyl-2,2,5-trimethyl-1,3-oxazolidone). The isoforms GST I and GST II are respectively a homodimer of 29-kDa (GST-29) subunits and a heterodimer of 29 and 27-kDa (GST-27) subunits, while GST I is twice as active with 1-chloro-2,4-dinitrobenzene as GST II, GST II is about seven times more active against the herbicide, alachlor. Western blotting using antisera raised against GST-29 and GST-27 showed that GST-29 is present throughout the maize plant prior to safener treatment. In contrast, GST-27 is only present in roots of untreated plants but is induced in all the major aerial organs of maize after root-drenching with safener. The amino-acid sequences of proteolytic fragments of GST-27 show that it is related to GST-29 and identical to the 27-kDa subunit of GST IV.Abbreviations CDNB 1-chloro-2,4-dinitrobenzene - DEAE di-ethylaminoethyl - FPLC fast protein liquid chromatography - GSH reduced glutathione - GST glutathione S-transferase - GST-26 26-kDa subunit of maize GST - GST-27 27-kDa subunit of maize GST - GST-29 29-kDa subunit of maize GST - R-25788 safener N,N-diallyl-2-dichloroacetamide - R-29148 safener 3-dichloroacetyl-2,2,5-trimethyl-1,3-oxazolidone - RPLC reverse phase liquid chromatography We are grateful to M-M. Lay, ZENECA AG Products (formerly ICI Americas), Richmond, Calif., USA for providing [¹⁴C] R-25788. ZENECA Seeds in the UK is part of ZENECA Limited.     

Characterization of diazotrophic bacteria associated with maize: effect of plant genotype, ontogeny and nitrogen-supply

Summary The population size of diazotrophic bacteria naturally associated with the maize rhizosphere can be affected by biotic and environmental factors. In this work we have evaluated the effect of two genotypes of maize, with and without nitrogen fertilization, on the population dynamics and distribution of diazotrophic bacteria associated with maize plants over different plant ontogenic stages. The study was carried out in a field experiment with and without nitrogen fertilization, using two maize cultivars (Santa Helena 8447 and Santa Rosa 3063) previously selected from 32 maize cultivars for the lowest and highest response to nitrogen fertilization, respectively. Microbiological and molecular approaches were used to characterize the diazotrophic bacterial population structure. Bacterial population was assessed by the most probable number using semi-solid N-free media, and by DNA isolation from soil and plant tissue followed by amplification of nifH gene fragments using nested PCR, and by RFLP analysis using the restriction endonucleases TaqI and HaeIII. The dynamics of the diazotrophic bacterial population were affected by the ontogenic stage of the maize plants, but not by the cultivar type. Roots were the preferred site of colonization, independent of cultivar type and growth stage. During the first stage of maize growth, addition of nitrogen fertilizer negatively affected the diazotrophic bacterial population.     

Spore production and mycorrhizal development in various tropical crop hosts infected with Glomus clarum

Plant growth, mycorrhizal development and vesicular arbuscular spore production were examined in five tropical crop host species inoculated with Glomus clarum and grown in a glasshouse. In one of the two experiments, sequential harvests of maize, sorghum and chickpea were made in order to study spore production in relation to plant growth and mycorrhizal development. Spore numbers in each of these hosts increased at a fairly constant rate until maximum plant dry weight, when spore production ceased. Sorghum and maize produced considerably more spores than chickpea, with spore numbers being closely correlated with mycorrhizal root length. In the second experiment, Glomus clarum was cultured on each of maize, millet, sorghum, groundnut and chickpea for three consecutive generations before cross-inoculation of the spores from each host onto all five hosts. Sporulation with respect to host size was generally greatest when the inoculum used to infect a host had been produced on that host. The growth-promoting effects of the fungus were not influenced by the source of the inoculum. More spores were produced on the cereals than the legumes. Differences in spore numbers amongst hosts and plant generations were apparently influenced mainly by infected root length and by the growth period.     

Overflow metabolism during anaerobic growth of Klebsiella aerogenes NCTC 418 on glycerol and dihydroxyacetone in chemostat culture

Klebsiella aerogenes NCTC 418 was grown anaerobically in chemostat culture with glycerol as source of carbon and energy. Glycerol-limited cultures did not ferment the carbon source with maximal efficiency but produced considerable amounts of 1,3-propanediol. The fraction of glycerol converted to this product depended on the growth rate and on the limitation: faster growing cells produced relatively more of this compound. Under glycerol excess conditions the energetic efficiency of fermentation was decreased due to the high 1,3-propanediol excretion rate. Evidence is presented that 1,3-propanediol accumulation exerts a profound effect on the cells' metabolic behaviour.When steady state glycerol-limited cultures were instantaneously relieved of the growth limitation a vastly enhanced glycerol uptake rate was observed, accompanied by a shift in the fermentation pattern towards 1,3-propanediol and acetate. This observation was consistent with the extremely high glycerol dehydrogenase activity that was measured in vitro. Some mechanisms that could be responsible for the energy dissipation during this response are discussed.     

Osmotic adjustment in Spirulina platensis

Unilateral irradiation of maize (Zea mays L.) seedlings results in a fluence-rate gradient, and hence below saturation, a gradient of the far-red-absorbing form of phytochrome (Pfr). The Pfr-gradients established by blue, red and far-red light were spectrophotometrically measured in the mesocotyl. Based on these Pfr-gradients and the fluence-response curves of phytochrome photoconversion the fluence-rate gradients were calculated. The fluence-rate gradient in the blue (460 nm) was steeper than that in the red (665 nm), which in turn was steeper than that in the far-red light (725 nm). The fluence-rate ratios front to rear were 1:0.06 (460 nm), 1:0.2 (665 nm), and 1:0.33 (725 nm). The assumption that phytochrome-mediated phototropism of maize mesocotyls is caused by local phytochrome-mediated growth inhibition was tested in the following manner. Firstly, the Pfr response curve for growth inhibition was calculated; these calculations were based on measurements of Pfr-gradients and data from red-light-induced phototropism. Secondly, the Pfr response curve for growth inhibition was used as a basis for calculating fluence-response curves for blue-and far-red-light-induced phototropism. Finally, these calculated results were compared with experimental data. It was concluded that the threshold for phytochrome-mediated phototropism of maize mesocotyls reflects the apparent photoconversion cross section of phytochrome whereas the maximal inducable curvature depends on the steepness of the light (Pfr) gradient across the mesocotyl.Abbreviations Pfr far-red-absorbing form of phytochrome - Ptot total phytochrome - Fr far-red light     

Gravitropic plant growth regulation and ethylene: an unsought cardinal coordinate for a disused model

According to the Cholodny-Went hypothesis, gravitropic differential growth is brought about by the redistribution of auxin (indolyl-3-acetic acid, IAA). We reinvestigated the relevance of different auxins and studied the role of ethylene in hypocotyls of sunflower and shoots and roots of rye and maize seedlings. Incubation of coleoptiles and of sunflower hypocotyls in solutions of IAA and dichlorophenoxyacetic acid as well as naphthylacetic acid resulted in a two- to threefold length increase compared to water controls. In spite of this pronounced general effect on elongation growth, gravi-curvature was similar to water controls. In contrast to this, inhibition of ethylene synthesis by aminoethoxyvinylglycine prevented differential growth of both hypocotyls and coleoptiles and of roots of maize. In horizontally stimulated maize roots growing on surfaces, inhibition of ethylene perception by methylcyclopropene inhibited roots to adapt growth to the surface, resulting in a lasting vertical orientation of the root tips. This effect is accompanied by up- and down-regulation of a number of proteins as detected by two-dimensional matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. Together the data query the regulatory relevance of IAA redistribution for gravitropic differential growth. They corroborate the crucial regulatory role of ethylene for gravitropic differential growth, both in roots and coleoptiles of maize as well as in hypocotyls.     

Antifungal and Root Surface Colonization Properties of GFP-Tagged Paenibacillus brasilensis PB177

Summary This study evaluates the potential of Paenibacillus brasilensis strain PB177 to inhibit phytopathogenic fungi commonly causing maize diseases and to colonize maize plants. In vitro assays demonstrated antagonistic activity against the fungal pathogens, Fusarium moniliforme and Diplodia macrospora. The PB177 strain was tagged with the gfp gene, encoding the green fluorescent protein (GFP) and GFP-tagged bacteria were detected attached to maize roots by stereo- and confocal microscopy. The GFP-tagged bacteria were also used to treat maize seeds before challenging the seeds with two phytopathogenic fungi. The results demonstrated that the bacterial cells are mobilized to the maize roots in the presence of the fungal pathogens. The ability of P. brasilensis PB177 to inhibit fungal growth in vitro and its capability of colonization of maize roots in vivo suggest a potential application of this strain as a biological control agent. This is the first report on the successful introduction of the GFP marker gene into a P. brasilensis strain, enabling the direct observation of these promising plant growth promoting bacteria on maize roots in situ.     

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.     

Maize and pigweed response to nitrogen supply and form

As nitrogen management practices change to achieve economic and environmental goals, effects on weed-crop competition must be examined. Two greenhouse experiments investigated the influence of N amount and form on growth of maize and redroot pigweed (Amaranthus retroflexus L.). In Experiment 1, maize and pigweed were grown together in a replacement series (maize: pigweed ratios of 0:4, 1:3, 2:2, 3:1, 4:0) under three NH₄NO₃-N supplies (0, 110, and 220 mg N kg^-1 soil). Maize was planted into established pigweed and plants were harvested 24 days after maize germination. Pigweed responded more to supplemental N than maize and accumulated 2.5 times as much N in shoots at the high N supply. Competition effects were not significant. Maize and pigweed were grown separately in Experiment 2 and supplied 220 mg N kg^-1 as either Ca(NO₃)₂ or (NH₄)₂SO₄ plus a nitrification inhibitor (enhanced ammonium supply, EAS). In maize, EAS treatment did not affect shoot growth and reduced root growth 25% relative to the NO₃-N treatment. In pigweed, shoot and root growth were restricted 23 and 86% by EAS treatment, respectively. Total plant N accumulation under EAS treatment was higher in maize, less in pigweed. Under EAS treatment, pigweed leaves were crinkled and chlorotic; leaf disks extracted in 70% ethanol, pH 3, contained less malate and oxalate but more NH₄ ⁺ compared to the NO₃-N treatment. Maize leaf disk malate levels were generally higher compared to pigweed but were less due to EAS treatment. Ammonium level in maize leaf disks was unaffected by N form and EAS treatment increased oxalate levels. Final bulk soil pH was generally lower in pots where pigweed were grown and tended to be lower due to EAS. Leaf disk malate levels and soil pH were positively associated. Results indicate that pigweed is more likely to compete with maize when high levels of NO₃-N are provided. Enhancing the proportion of N supplied as NH₄ ⁺ should restrict the growth of NH₄ ⁺-sensitive pigweed.     

Effect of Zero Tillage and Residues Conservation on Continuous Maize Cropping in a Subtropical Environment (Mexico)

The effects of zero tillage and residue conservation in continuous maize-cropping systems are poorly documented, especially in the tropics, and are expected to vary highly with climatic conditions and nitrogen availability. In the present study, maize was cultivated during the wet and dry seasons in central Mexico for three consecutive years, under different treatments combining tillage with residue management techniques and with nitrogen rates. In some treatments, maize was also intercropped with jackbean, Canavalia ensiformis L. (DC). Yield and yield components as well as physiological traits and soil characteristics were assessed during the wet and dry seasons for the third year of cultivation. During the wet season, zero tillage was associated with less biomass and grain yield. Leaf chlorophyll concentration was smaller under zero tillage, suggesting less nitrogen uptake. Both zero tillage and residue conservation reduced early growth and strongly increased ear rot. During the dry season, zero tillage was associated with greater root mass, as measured by electrical capacitance. Residue conservation decreased the anthesis-silking interval, suggesting better water uptake. There was, however, no significant effect of tillage or residue management practices on yield. Zero tillage was found to be associated with increased soil bulk density, nitrogen concentration and microbial biomass organic carbon. Residue conservation increased soil carbon concentration as well as microbial biomass organic carbon. Intercropping with jackbean and conservation of its residues in addition to maize residues increased soil nitrogen concentration. Further investigation may provide more information on the factors related to zero tillage and residue conservation that affect maize early growth, and determine to which extent the observed modifications of soil chemical and physical properties induced by conservation tillage will further affect maize yield.     

Nuclear DNA amount,growth, and yield parameters in maize

Extensive nuclear DNA content variation has been observed inZea mays. Of particular interest is the effect of this variation on the agronomic potential of maize. In the present study, yield and growth data were collected on 12 southwestern US maize open-pollinated populations. These populations, originally cultivated by the Indians of the southwestern US for both human and animal consumption and adapted to various altitudes, were grown in replicated plots at the University of Illinois Agronomy-Plant Pathology South Farm. All growth and yield parameters were found to be negatively correlated with nuclear DNA amount. The negative correlations of nuclear DNA amount and growth parameters were more pronounced at 60 days after planting (DAP) than 30 DAP. Agronomically-important yield parameters, such as ear or seed weight and seed number per plant, also exhibited a significant negative correlations with nuclear DNA amount. These correlations demonstrate how the nucleotype may exhibit a high degree of influence on the agronomic phenotype. Although the results presented here represent only three replications at one location in 1 year, the observations noted suggest that nucleotype plays an integral role in determining the agronomic performance of maize. Further studies are needed to fully document this role.     

Effect of a phosphate solubilizing bacteria on maize growth and root exudation over four levels of labile phosphorus

The influence of inoculation with phosphate-solubilizing bacteria (Enterobacter agglomerans) on maize growth, P uptake and root exudation was studied. Plants were grown in an axenic culture device where P was supplied as soluble phosphate at different contents (0, 5, 15 or 25 ppm) in the nutrient solution and as insoluble rock phosphate added to the culture sand. Experimental device was successfully used to obtain axenic root systems or good establishment of the inoculated strain in the rhizosphere of maize (10⁹ bact. g⁻¹ dry rhizospheric material). Plant growth was promoted by inoculation only for 5 or 15 ppm of soluble P in the nutrient medium without any significant effect on P uptake by the plant, suggesting that the quantities of P released by bacterial rhizospheric activity were very small. Amounts of organic compounds (total C and water-soluble C) exuded were relatively low (3.0 to 6.4% of the total plant biomass) and were reduced by bacterial inoculation when plant growth was largely promoted. Carbon balance modification and plant growth hormone production by the inoculated strain were suspected and discussed.     

Crossing maize with sorghum,Tripsacum and millet: the products and their level of development following pollination

Summary Maize was crossed with sorghum, Tripsacum and millet with the aim of introgressing desirable alien characteristics into maize. The products of crosses were analyzed as to their level of differentiation following pollination; their further development on artificial culture medium was compared. In spite of a stimulation rate close to 5%, no evidence of hybridization between maize and sorghum or millet could be obtained. The plants recovered proved to be of maternal origin. However, with an appreciable frequency, stimulation leading to hypertrophic growth of nucellar tissue was observed. This phenomenon is bound to pollination, never occurring in non-pollinated ears. In crosses involving Tripsacum, more than 140 true hybrids were isolated. The influence of the genotypes used as well as factors such as climatic conditions or in vitro techniques are discussed. Except for one haploid maize plant, all the plants recovered proved to be classical hybrids, most of them showing the expected complement of chromosomes from each parent (10 + 36 chromosomes), a few others being slightly hyperploid (2n = 47 to 50 chromosomes). No non-classical hybrids constituted by a nonreduced female gamete and a reduced male gamete were obtained.     

Genetic Analysis of Maize Root Characteristics in Response to Low Nitrogen Stress

Under low-input cropping systems, nitrogen (N) can be a limiting factor in plant growth and yield. Identifying genotypes that are more efficient at capturing limited N resources and the traits and mechanisms responsible for this ability is important. Root trait has a substantial influence on N acquisition from soils. Nevertheless, inconsistencies still exist as to the effect of low N on root length and its architecture in terms of lateral and axial roots. For maize, a crop utilizing heterosis, little is known about the relationship between parents and their crosses in the response of root architecture to N availability. Here 7 inbred maize lines and 21 of their crosses created by diallel mating were used to study the effect of N stress on root morphology as well as the relationship between the inbreds and their crosses. With large genotypic differences, low N generally suppresses shoot growth and increases the root to shoot ratio with or without increasing root biomass in maize. Maize plants responded to N deficiency by increasing total root length and altering root architecture by increasing the elongation of individual axial roots and enhancing lateral root growth, but with a reduction in the number of axial roots. Here, the inbreds showed weaker responses in root biomass and other root parameters than their crosses. Heterosis of root traits was significant at both N levels and was attributed to both the general combining ability (GCA) and special combining ability (SCA). Low N had substantial affects on the pattern of heterosis, GCA and SCA affects on root traits for each of the crosses suggesting that selection under N stress is necessary in generating low N-tolerant maize genotypes.     

Fumonisin B1, a toxin produced by <Emphasis Type="Italic">Fusarium verticillioides</Emphasis>, modulates maize β-1,3-glucanase activities involved in defense response

Fusarium verticillioides is an important pathogen in maize that causes various diseases affecting all stages of plant development worldwide. The fungal pathogen could be seed borne or survive in soil and penetrate the germinating seed. Most F. verticillioides strains produce fumonisins, which are of concern because of their toxicity to animals and possibly humans, and because they enhance virulence against seedlings of some maize genotypes. In this work, we studied the action of fumonisin B1 (FB1) on the activity of maize β-1,3-glucanases involved in plant defense response. In maize embryos, FB1 induced an acidic isoform while suppressing the activity of two basic isoforms. This acidic isoform was induced also with 2,6-dichloroisonicotinic acid, an analog of salicylic acid. Repression of the basic isoforms suggested a direct interaction of the enzymes with the mycotoxin as in vitro experiments showed that pure FB1 inhibited the basic β-1,3-glucanases with an IC₅₀ of 53 μM. When germinating maize embryos were inoculated with F. verticillioides the same dual effect on β-1,3-glucanase activities that we observed with the pure toxin was reproduced. Similar levels of FB1 were recovered at 24 h germination in maize tissue when they were treated with pure FB1 or inoculated with an FB1-producing strain. These results suggest that β-1,3-glucanases are a relevant physiological target and their modulation by FB1 might contribute to F. verticillioides colonization.     

Comparative responses of tetraploid wheats pollinated with Zea mays L. and Hordeum bulbosum L.

Ten different tetraploid wheat (Triticum turgidum) genotypes were pollinated with maize (Zea mays). Fertilization was achieved in all ten genotypes and no significant difference in fertilization frequency between the tetraploid wheat genotypes was detected. A mean of 41.1% of pollinated ovaries contained an embryo. All these crosses were characterized by the elimination of the maize chromosomes, and the resulting embryos were haploids. Six of the tetraploid wheat genotypes were also pollinated with Hordeum bulbosum. Fertilization frequencies with H. bulbosum were much lower (mean=13.4%), and significant differences between the tetraploid wheat genotypes were detected. Observation of pollen tube growth revealed that part of the incompatibility reaction between tetraploid wheats and H. bulbosum was due to an effect similar to that of the Kr genes, namely pollen tube growth inhibition. These results indicate that pollinations with maize may have potential as a broad spectrum haploid production system for tetraploid wheats. Present address: Agriculture Canada, Research Branch, Central Experimental Farm, Bldg 50, Ohawa, Ontario, Canada K1A OC6     

Induction of systemic acquired resistance in Zea mays L. by Aspergillus flavus and A. parasiticus derived elicitors

Host defence mechanisms can be elicited by using different elicitors produced from the pathogen/host. In this study, an effort has been made to study the effect of two fungal elicitors derived from Aspergillus flavus and A. parasiticus on induction of various defence-related enzymes in maize (Zea mays L.). Foliar application was done on 20-days-old maize plant with 10% A. flavus fungal culture filtrate (AFFCF) and A. parasiticus fungal culture filtrate (APFCF) as elicitors to trigger systemic acquired resistance (SAR). As a response of SAR, an increase in activities of phenylalanine ammonia lyase (PAL), peroxidase (POX), β-1,3-glucanase, nitrate reductase (NR) and nitrite reductase (NiR), total proteins were found highest on 4th day after treatment (DAT), whereas total carbohydrate and total chlorophyll on 2nd and 6th DAT, respectively, in comparison with the control plants. The SDS PAGE analysis revealed the induction of PR proteins, namely Chitinase (25, 29?kDa) and β-1,3-glucanase (33?kDa), in treated plants in comparison with untreated control plants. The treated plants showed enhanced growth and development as well as increase in yield. About 100% survival rate was found in maize seeds treated with AFFCF and APFCF and grown on respective fungal infested soil than control. The enhanced activities of defence enzymes and elevated protein, carbohydrate, chlorophyll content in treated maize plants suggest the induction of SAR against A. flavus and A. parasiticus by using the same fungal elicitors.     

Molecular cloning and heterologous expression of beta1,2-xylosyltransferase and core alpha1,3-fucosyltransferase from maize

Maize is considered a promising alternative production system for pharmaceutically relevant proteins. However, like in all other plant species asparagine-linked oligosaccharides of maize glycoproteins are modified with beta1,2-xylose and core alpha1,3-fucose sugar residues, which are considered to be immunogenic in mammals. This altered N-glycosylation when compared to mammalian cells may reduce the potential of maize as a production system for heterologous glycoproteins. Here we report the cloning and characterization of the cDNA sequences coding for the maize enzymes beta1,2-xylosyltransferase (XylT) and core alpha1,3-fucosyltransferase (FucT). The cloned XylT and FucT cDNAs were shown to encode enzymatically active proteins, which were independently able to convert a mammalian acceptor glycoprotein into an antigen binding anti-plant N-glycan antibodies. The complete sequence of the XylT gene was determined. Evidence for the presence of at least three XylT and FucT gene loci in the maize genome was obtained. The identification of the two enzymes and their genes will allow the targeted downregulation or even elimination of beta1,2-xylose and core alpha1,3-fucose addition to recombinant glycoproteins produced in maize.