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Maize Plants (maize + plant)
Kinds of Maize Plants Selected AbstractsThe effect of temperature on C4 -type leaf photosynthesis parametersPLANT CELL & ENVIRONMENT, Issue 9 2007RAIA-SILVIA MASSAD ABSTRACT C4 -type photosynthesis is known to vary with growth and measurement temperatures. In an attempt to quantify its variability with measurement temperature, the photosynthetic parameters , the maximum catalytic rate of the enzyme ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) (Vcmax), the maximum catalytic rate of the enzyme phosphoenolpyruvate carboxylase (PEPC) (Vpmax) and the maximum electron transport rate (Jmax) , were examined. Maize plants were grown in climatic-controlled phytotrons, and the curves of net photosynthesis (An) versus intercellular air space CO2 concentrations (Ci), and An versus photosynthetic photon flux density (PPFD) were determined over a temperature range of 15,40 °C. Values of Vcmax, Vpmax and Jmax were computed by inversion of the von Caemmerer & Furbank photosynthesis model. Values of Vpmax and Jmax obtained at 25 °C conform to values found in the literature. Parameters for an Arrhenius equation that best fits the calculated values of Vcmax, Vpmax and Jmax are then proposed. These parameters should be further tested with C4 plants for validation. Other model key parameters such as the mesophyll cell conductance to CO2 (gi), the bundle sheath cells conductance to CO2 (gbs) and Michaelis,Menten constants for CO2 and O2 (Kc, Kp and Ko) also vary with temperature and should be better parameterized. [source] Heritable targeted mutagenesis in maize using a designed endonucleaseTHE PLANT JOURNAL, Issue 1 2010Huirong Gao Summary The liguleless locus (liguleless1) was chosen for demonstration of targeted mutagenesis in maize using an engineered endonuclease derived from the I- CreI homing endonuclease. A single-chain endonuclease, comprising a pair of I- CreI monomers fused into a single polypeptide, was designed to recognize a target sequence adjacent to the LIGULELESS1 (LG1) gene promoter. The endonuclease gene was delivered to maize cells by Agrobacterium -mediated transformation of immature embryos, and transgenic T0 plants were screened for mutations introduced at the liguleless1 locus. We found mutations at the target locus in 3% of the T0 plants, each of which was regenerated from independently selected callus. Plants that were monoallelic, biallelic and chimeric for mutations at the liguleless1 locus were found. Relatively short deletions (shortest 2 bp, longest 220 bp) were most frequently identified at the expected cut site, although short insertions were also detected at this site. We show that rational re-design of an endonuclease can produce a functional enzyme capable of introducing double-strand breaks at selected chromosomal loci. In combination with DNA repair mechanisms, the system produces targeted mutations with sufficient frequency that dedicated selection for such mutations is not required. Re-designed homing endonucleases are a useful molecular tool for introducing targeted mutations in a living organism, specifically a maize plant. [source] Reprogramming a maize plant: transcriptional and metabolic changes induced by the fungal biotroph Ustilago maydisTHE PLANT JOURNAL, Issue 2 2008Gunther Doehlemann Summary The fungal pathogen Ustilago maydis establishes a biotrophic relationship with its host plant maize (Zea mays). Hallmarks of the disease are large plant tumours in which fungal proliferation occurs. Previous studies suggested that classical defence pathways are not activated. Confocal microscopy, global expression profiling and metabolic profiling now shows that U. maydis is recognized early and triggers defence responses. Many of these early response genes are downregulated at later time points, whereas several genes associated with suppression of cell death are induced. The interplay between fungus and host involves changes in hormone signalling, induction of antioxidant and secondary metabolism, as well as the prevention of source leaf establishment. Our data provide novel insights into the complexity of a biotrophic interaction. [source] Costs of cannibalism in the presence of an iridovirus pathogen of Spodoptera frugiperdaECOLOGICAL ENTOMOLOGY, Issue 2 2006Trevor Williams Abstract., 1.,The costs of cannibalism were examined in larvae of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in the presence of conspecifics infected by a lethal invertebrate iridescent virus (IIV). The hypothesis of a positive correlation between insect density and the likelihood of disease transmission by cannibalism was examined in laboratory microcosms and a field experiment. 2.,Transmission was negligible following peroral infection of early instars with purified virus suspensions or following coprophagy of virus-contaminated faeces excreted by infected insects. In contrast, 92% of the insects that predated infected conspecifics acquired the infection and died prior to adult emergence in the laboratory. Diseased larvae were more likely to be victims of cannibalism than healthy larvae. 3.,The prevalence of cannibalism was density dependent in laboratory microcosms with a low density (10 healthy insects + one infected insect) or high density (30 healthy insects + one infected insect) of insects, and field experiments performed on maize plants infested with one or four healthy insects + one infected insect. 4.,Cannibalism in the presence of virus-infected conspecifics was highly costly to S. frugiperda; in all cases, insect survival was reduced by between ,,50% (laboratory) and ,,30% (field) in the presence of the pathogen. Contrary to expectations, the prevalence of disease was not sensitive to density because cannibalism resulted in self-thinning. As infected individuals are consumed and disappear from the population, the prevalence of disease will be determined by the timescale over which transmission can be achieved, and the rate at which individuals that have acquired an infection become themselves infectious to conspecific predators. [source] Different portions of the maize root system host Burkholderia cepacia populations with different degrees of genetic polymorphismENVIRONMENTAL MICROBIOLOGY, Issue 1 2000Luigi Chiarini In order to acquire a better understanding of the spatial and temporal variations of genetic diversity of Burkholderia cepacia populations in the rhizosphere of Zea mays, 161 strains were isolated from three portions of the maize root system at different soil depths and at three distinct plant growth stages. The genetic diversity among B. cepacia isolates was analysed by means of the random amplified polymorphic DNA (RAPD) technique. A number of diversity indices (richness, Shannon diversity, evenness and mean genetic distance) were calculated for each bacterial population isolated from the different root system portions. Moreover, the analysis of molecular variance ( amova) method was applied to estimate the genetic differences among the various bacterial populations. Our results showed that, in young plants, B. cepacia colonized preferentially the upper part of the root system, whereas in mature plants, B. cepacia was mostly recovered from the terminal part of the root system. This uneven distribution of B. cepacia cells among different root system portions partially reflected marked genetic differences among the B. cepacia populations isolated along maize roots on three distinct sampling occasions. In fact, all the diversity indices calculated indicated that genetic diversity increased during plant development and that the highest diversity values were found in mature maize plants, in particular in the middle and terminal portions of the root system. Moreover, the analysis of RAPD patterns by means of the amova method revealed highly significant divergences in the degree of genetic polymorphism among the various B. cepacia populations. [source] Effect of Salt Stress on the Salicylic Acid Synthesis in Young Maize (Zea mays L.) PlantsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2009G. Szalai Abstract The effect of salt stress on salicylic acid (SA) synthesis was investigated parallel with the induction of antioxidant enzymes in young maize plants. Two-week-old maize plants grown in hydroponic solution were treated with 50 or 100 mm NaCl for 7 days. Antioxidant enzyme activities, and the SA and o -hydroxy-cinnamic acid (oHCA) levels were measured on the 3rd and 7th day of treatment and after 4 days of recovery. Ascorbate peroxidase activity increased in the leaves, but changes in guaiacol peroxidase activity only could be detected in the roots after 7 days. Glutathione reductase activity increased both in the leaves and in the roots after the 3rd day of 100 mm NaCl treatment. Free SA only increased during recovery in the leaves and roots. In the leaves of plants treated with 100 mm NaCl, a slight increase was observed in the free oHCA level, which rose dramatically after recovery, while in the roots an increase could only be seen after recovery. These results suggest that oHCA may serve not only as a precursor of SA but may also have an antioxidant role during salt stress and recovery. [source] Cadmium Enhances Generation of Hydrogen Peroxide and Amplifies Activities of Catalase, Peroxidases and Superoxide Dismutase in MaizeJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2008P. Kumar Abstract Maize (Zea mays L. cv. 777) plants grown in hydroponic culture were treated with 50 ,m CdSO4. Growth and metabolic parameters indicative of oxidative stress and antioxidant responses were studied in leaves of plants treated with Cd. Apart from increasing lipid peroxidation and H2O2 accumulation, supply of Cd suppressed growth, fresh and dry mass of plants and decreased the concentrations of chloroplastic pigments. The activities of catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), ascorbate peroxidase (APX; EC 1.11.1.11) and superoxide dismutase (SOD; EC 1.15.1.1) were increased in plants supplied 50 ,m Cd. Localization of activities of isoforms of these enzymes (POD, APX and SOD) on native gels also revealed increase in the intensities of pre-existing bands. Stimulated activities of CAT, POD, APX and SOD in maize plants supplied excess Cd do not appear to have relieved plants from excessive generation of reactive oxygen species (ROS). It is, therefore, concluded that supply of 50 ,m Cd induces oxidative stress by increasing production of ROS despite increased antioxidant protection in maize plants. [source] Biostimulant activity of two protein hydrolyzates in the growth and nitrogen metabolism of maize seedlingsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2009Andrea Ertani Abstract Two protein hydrolyzate,based fertilizers (PHFs), one from alfalfa (AH) and one from meat flour (MFH), were studied chemically and biologically. AH and MFH revealed a different degree of hydrolysis and a different amino acid composition. The biostimulant activity was investigated using two specific and sensitive bioassays of auxins and gibberellins. Extracts of AH and MFH elicited a gibberellin-like activity and a weak auxin-like one. To improve our understanding of the biostimulant activity, AH and MFH were supplied to maize plants and their effect on growth and nitrate metabolism was studied. Both PHFs increased root and leaf growth and induced morphological changes in root architecture. Besides, the treatments increased nitrate reductase (NR) and glutamine synthetase (GS) activities, suggesting a positive role of the two hydrolyzates in the induction of nitrate conversion into organic nitrogen. Moreover, treatments enhanced GS1 and GS2 isoforms in maize leaves. The latter isoform, amounting to 5- to 7-fold the level of the former, appears to be a superior form in the assimilation of ammonia. The high NR and GS activities together with the high induction of GS isoforms indicate a stimulatory effect of the two PHFs on the assimilation of nitrate. In addition, a role of amino acids and small peptides of the two PHFs is suggested in the regulation of the hormone-like activity and nitrogen pathway. [source] Effects of decreasing soil water content on seminal lateral roots of young maize plantsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2006Abstract Soil micropores that contain water at or below field capacity cannot be invaded by seminal or first-order lateral roots of maize plants because their root diameters are larger than 10 ,m. Hence, at soil-water levels below field capacity plant roots must establish a new pore system by displacement of soil particles in order to access soil water. We investigated how decreasing soil water content (SWC) influences growth and morphology of the root system of young maize plants. Plants were grown in rhizotrons 40,cm wide, 50,cm high, and approximately 0.7,cm thick. Five SWC treatments were established by addition of increasing amounts of water to soil and thorough mixing before filling the rhizotrons. No water was added to treatments 1,4 throughout the experiment. Treatment 5 was watered frequently throughout the experiment to serve as a control. Seminal-root length and SWC in soil layers 0,10, 10,20, 20,30, 30,40, and 40,50,cm were measured at intervals of 2,3 d on scanner images by image analysis. At 15 d after planting, for treatments 1,4 shoot dry weight and total root length were directly related to the amount of water added to the soil, and for treatments 4 and 5, total root length and shoot dry weights were similar. Length of seminal roots visible at the transparent surface of the rhizotron for all treatments was highest in the uppermost soil layer and decreased with distance from the soil surface. For all layers, seminal-root elongation rate was at maximum above a SWC of 0.17,cm3,cm,3, corresponding to a matric potential of ,30 kPa. With decreasing SWC, elongation rate decreased, and 20% of maximum seminal root elongation rate was observed below SWC of 0.05,cm3,cm,3. After destructive harvest for treatment 1,4, number of (root-) tips per unit length of seminal root was found uninfluenced over the range of initial SWC from 0.10 to 0.26,cm3,cm,3. However, initial SWC close to the permanent wilting point strongly increased number of tips. Average root length of first-order lateral (FOL) roots increased as initial SWC increased, and the highest length was found for the frequently watered treatment 5. The results of the study suggest that the ability to produce new FOL roots across a wide range of SWC may give maize an adaptive advantage, because FOL root growth can rapidly adapt to changing soil moisture conditions. [source] Does H+ pumping by plasmalemma ATPase limit leaf growth of maize (Zea mays) during the first phase of salt stress?JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2005Christian Zörb Abstract In the first phase of salt stress, growth of plants is impaired mainly by osmotic stress. To elucidate the effect of NaCl salinity on elongation growth of maize leaves in the first phase of salt stress, we investigated the effect of NaCl on gene expression and activity of the plasmalemma H+ ATPase of elongating leaves of maize (Zea mays L.). Treatment of maize plants with 125 mM NaCl for 3 d decreased leaf growth relative to control plants (1 mM NaCl). Whereas H+ ATPase hydrolytic activity was unaffected, the ability of the H+ ATPase to establish a pH gradient was strongly reduced. Total mRNA of plasmalemma H+ ATPase was slightly increased. However, mRNA of the ATPase isoform MHA1 was significantly reduced and ATPase isoform MHA4 was strongly increased at the mRNA level. Synthesis of total H+ ATPase protein was unchanged as revealed by western blot. The results indicate that reduced pumping of H+ ATPase in leaf plasmalemma under salt stress may be caused by a switch to gene expression of the specific isoform MHA4, which shows inferior H+ -pumping efficiency in comparison to isoforms expressed under control conditions. We propose that reduced H+ pumping of plasmalemma H+ ATPase is involved in the reduction of leaf growth of maize during the first phase of salt stress. Limitiert die H+ -Pumpaktivität der Plasmalemma-ATPase das Blattwachstum von Mais (Zea mays) während der ersten Phase eines Salzstresses? In der ersten Phase eines Salzstresses wird das Pflanzenwachstum hauptsächlich durch osmotischen Stress beeinträchtigt. Zur Klärung des Einflusses der NaCl-Salinität auf das Streckungswachstum von Maisblättern in der ersten Phase eines Salzstresses wurde der Einfluss von NaCl auf die Genexpression und die Aktivität der H+ -ATPase im Plasmalemma von unter Salzstress wachsenden Maisblättern (Zea mays L.) untersucht. Dreitägige Behandlung von Maispflanzen mit 125 mM NaCl verminderte im Vergleich zu Kontrollpflanzen (1 mM NaCl) das Blattwachstum. Während die hydrolytische H+ -ATPase-Aktivität unbeeinflusst blieb, wurde die Fähigkeit, einen pH-Gradienten aufzubauen, stark reduziert. Die Gesamt-mRNA der H+ -ATPase war unverändert. Während jedoch die ATPase-Isoform MHA1 signifikant vermindert war, wurde die Isoform MHA4 auf dem mRNA-Niveau stark erhöht. Die Western-Blot-Analyse zeigte keine Veränderung der Menge des Gesamtproteins der H+ -ATPase. Unsere Ergebnisse sprechen dafür, dass die reduzierte Fähigkeit der H+ -ATPase im Plasmalemma von unter Salzstress gewachsenen Blättern einen pH-Gradienten aufzubauen, durch Genexpression der spezifischen Isoform MHA4 verursacht wird. Diese Isoform weist eine geringere H+ -Pumpeffizienz im Vergleich zu Isoformen auf, die unter Kontrollbedingungen gebildet werden. Wir schlagen daher vor, dass die reduzierte Fähigkeit der H+ -ATPase einen pH-Gradienten aufzubauen, an der Verminderung des Blattwachstums von Mais in der ersten Phase des Salzstresses beteiligt ist. [source] Effects of soil bulk density on seminal and lateral roots of young maize plants (Zea mays L.)JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2004Rolf O. Kuchenbuch Abstract It is well established that increasing soil bulk density (SBD) above some threshold value reduces plant root growth and thus may reduce water and nutrient acquisition. However, formation and elongation of maize seminal roots and first order lateral (FOL) roots in various soil layers under the influence of SBD has not been documented. Two studies were conducted on a loamy sand soil at SBD ranging from 1.25 g,cm,3 to 1.66 g,cm,3. Rhizotrons with a soil layer 7 mm thick were used and pre-germinated plants were grown for 15 days. Over the range of SBD tested, the shoot growth was not influenced whereas total root length was reduced by 30,% with increasing SBD. Absolute growth rate of seminal roots was highest in the top soil layer and decreased with increasing distance from the surface. Increasing SBD amplified this effect by 20,% and 50,% for the top soil layer and lower soil layers, respectively. At the end of the experiment, total seminal roots attributed to approximately 15,% of the total plant root length. Increasing SBD reduced seminal root growth in the lowest soil layer only, whereas FOL root length decreased with SBD in all but the uppermost soil layer. For FOL, there was a positive interaction of SBD with distance from the soil surface. Both, increasing SBD and soil depth reduced root length by a reduction of number of FOL roots formed while the length of individual FOL roots was not influenced. Hence, increasing SBD may reduce spatial access to nutrients and water by (i) reducing seminal root development in deeper soil layers, aggravated by (ii) the reduction of the number of FOL roots that originate from these seminal roots. Einfluss der Bodendichte auf Seminal- und Lateralwurzeln von jungen Maispflanzen (Zea mays L.) Es ist bekannt, dass zunehmende Bodendichte (SBD) oberhalb eines Grenzwertes das Wurzelwachstum von Pflanzen und die Wasser- und Nährstoffaufnahme reduziert. Bildung und Wachstum der Seminal- und der Lateralwurzeln erster Ordnung (FOL) von Mais in Bodenschichten verschiedenen Abstands von der Bodenoberfläche unter dem Einfluss verschiedener Bodendichten wurde bisher nicht beschrieben. Zwei unabhängige Versuche wurden mit einem lehmigen Sandboden durchgeführt. Vorgekeimte Maiskörner wurden in Rhizotrone mit einer etwa 7,mm dicken Bodenschicht eingesetzt, die Bodendichten lagen im Mittel der Rhizotrone zwischen 1,25 g,cm,3 und 1,66 g,cm,3. Die Versuchsdauer betrug 15 Tage. Über den Bereich der geprüften SBD wurde das Sprosswachstum nicht beeinflusst, während die Gesamtwurzellänge mit zunehmender SBD um bis zu 30,% abnahm. Die absolute Wachstumsrate der Seminalwurzeln war in der obersten Bodenschicht am höchsten und nahm mit zunehmendem Abstand von der Bodenoberfläche ab. Seminalwurzeln trugen zu ca. 15,% zur Gesamtwurzellänge bei. Zunehmende SBD reduzierte das Wachstum der Seminalwurzeln nur in der untersten Bodenschicht. Demgegenüber wurden die Längen der FOL in allen außer der obersten Schicht bei zunehmender SBD verringert. Bei den FOL wurde eine positive Interaktion zwischen SBD und Abstand von der Bodenoberfläche festgestellt. Sowohl zunehmende SBD als auch zunehmende Tiefe reduzierte die Wurzellänge durch eine Verringerung der Anzahl an FOL, während deren Länge nicht beeinflusst wurde. Folglich kann zunehmende SBD die räumliche Zugänglichkeit zu Wasser und Nährstoffen für die Pflanzen dadurch beeinflussen, dass (i) die Entwicklung von Seminalwurzeln in tieferen Bodenschichten reduziert wird und dass dieser Effekt verstärkt wird durch (ii) die verringerte Bildung von FOL an Seminalwurzeln. [source] Comparison of different phosphorus-fertiliser matrices to induce the recovery of phosphorus-deficient maize plantsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2009Javier Erro Abstract BACKGROUND: Previous studies have demonstrated the capacity of a new type of mineral fertiliser, known as rhizosphere-controlled fertiliser (RCF), to supply adequate nutrition to plants while minimising nutrient losses. This fertiliser family is based on the presence a phosphoric matrix composed of metal,humic,phosphates, soluble not in water but in the rhizospheric acids released by plant roots as an expression of nutritional needs, principally citric acid. The aim of this study is to investigate the capacity of the RCF matrix and other phosphorus-containing products to induce the recovery of phosphorus-deficient maize plants. RESULTS: The results showed that RCF-based P fertilisers were able to facilitate plant recovery, measured by the dry root and shoot weights, to the same extent as a water-soluble P fertiliser (monopotassium phosphate). This fact was well correlated to both the variation pattern of citric and trans -aconitic acids in the shoot and roots during the treatment, and P shoot and root contents. Likewise the analysis of the variation of P concentration in the nutrient solution during the treatment indicates that plant recovery is associated with the capacity of the plant to mobilise P from the different fertiliser matrices studied. CONCLUSION: These results confirm the findings obtained in previous in vitro studies and indicate the suitability of RCF strategy for the preparation of mineral fertilisers with a nutrient release pattern more sensitive to plant nutritional needs. Copyright © 2009 Society of Chemical Industry [source] Bacterial diversity in maize rhizospheres: conclusions on the use of genetic profiles based on PCR-amplified partial small subunit rRNA genes in ecological studiesMOLECULAR ECOLOGY, Issue 1 2003Achim Schmalenberger Abstract A cultivation-independent approach based on polymerase chain reaction (PCR)-amplified partial small subunit rRNA genes and genetic profiling by single-strand conformation polymorphism (SSCP) was used to characterize the bacterial diversity inhabiting the rhizosphere of maize plants grown on an agricultural field. The community structures of two cultivars, a genetically engineered and a nonengineered variety, different herbicide regimes and soil tillage were compared with each other at two sampling dates. SSCP-profiles were generated with DNA from bacterial cell consortia with primers hybridizing to evolutionarily highly conserved rRNA gene regions. On silver-stained gels, each profile consisted of approx. 50 distinguishable bands. Similarity analyses of patterns recorded by digital image analyses could not detect any difference between cultivars or treatments that was greater than the variability between replicates. A total of 54 sequences recovered from different bands were identified and grouped into operational taxonomical units (OTUs). Surprisingly, only five of 40 OTUs contained sequences of both samplings. Three different bands from a profile were selected to test whether this small overlap was due to an incomplete recovery of sequences. From a faint band, two different OTUs were found when 12 clones were analysed, and from two strong bands 24 and 22 OTUs were detected from a total of 26 and 36 clones, respectively. The OTUs belonged to phylogenetically different groups of bacteria. Gene probes that were developed to target different bands of the profiles, however, indicated in Southern blot analyses that patterns between treatments, replicates and samplings, and even from two different growing seasons were highly conserved. Our study demonstrates that community profiles can consist of more sequences than detectable by staining and that gene probes in Southern blot can be a useful control to investigate the composition of microbial communities by genetic profiles. [source] Distribution and metabolism of D/L -, L - and D -glufosinate in transgenic, glufosinate-tolerant crops of maize (Zea mays L ssp mays) and oilseed rape (Brassica napus L var napus),PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2004Monika Ruhland Abstract The aim of the present study was to determine whether post-emergence application of glufosinate to transgenic crops could lead to an increase in residues or to the formation of new, hitherto unknown metabolites. Transgenic oilseed rape and maize plants were treated separately with L -glufosinate, D -glufosinate or the racemic mixture. Whereas about 90% of the applied D -glufosinate was washed off by rain and only 5,6% was metabolised, 13,35% of the applied L -glufosinate remained in the form of metabolites and unchanged herbicide in both transgenic maize and oilseed rape. The main metabolite was N -acetyl- L -glufosinate with total residues of 91% in oilseed rape and 67% in maize, together with small amounts, of 5% in oilseed rape and 28% in maize, of different methylphosphinyl fatty acids. These metabolites were probably formed from L -glufosinate by deamination and subsequent decarboxylation. The residues were distributed in all fractions of the plants, with the highest contents in treated leaves and the lowest in the grains (0.07,0.3% in maize and 0.4,0.6% in oilseed rape). There was no indication of an accumulation of total residues or of residue levels above the official tolerances for glufosinate. Copyright © 2004 Society of Chemical Industry [source] Transgenic maize lines with cell-type specific expression of fluorescent proteins in plastidsPLANT BIOTECHNOLOGY JOURNAL, Issue 2 2010Amir Sattarzadeh Summary Plastid number and morphology vary dramatically between cell types and at different developmental stages. Furthermore, in C4 plants such as maize, chloroplast ultrastructure and biochemical functions are specialized in mesophyll and bundle sheath cells, which differentiate acropetally from the proplastid form in the leaf base. To develop visible markers for maize plastids, we have created a series of stable transgenics expressing fluorescent proteins fused to either the maize ubiquitin promoter, the mesophyll-specific phosphoenolpyruvate carboxylase (PepC) promoter, or the bundle sheath-specific Rubisco small subunit 1 (RbcS) promoter. Multiple independent events were examined and revealed that maize codon-optimized versions of YFP and GFP were particularly well expressed, and that expression was stably inherited. Plants carrying PepC promoter constructs exhibit YFP expression in mesophyll plastids and the RbcS promoter mediated expression in bundle sheath plastids. The PepC and RbcS promoter fusions also proved useful for identifying plastids in organs such as epidermis, silks, roots and trichomes. These tools will inform future plastid-related studies of wild-type and mutant maize plants and provide material from which different plastid types may be isolated. [source] A Cre::FLP fusion protein recombines FRT or loxP sites in transgenic maize plants,PLANT BIOTECHNOLOGY JOURNAL, Issue 8 2008Vesna Djukanovic Summary The coding sequences of Cre (site-specific recombinase from bacteriophage P1) and FLP (yeast 2-µm plasmid site-specific recombinase) were fused in frame to produce a novel, dual-function, site-specific recombinase gene. Transgenic maize plants containing the Cre::FLP fusion expression vector were crossed to transgenic plants containing either the loxP or FRT excision substrate. Complete and precise excisions of chromosomal fragments flanked by the respective target sites were observed in the F1 and F2 progeny plants. The episomal DNA recombination products were frequently lost. Non-recombined FRT substrates found in the F1 plants were recovered in the F2 generation after the Cre::FLP gene segregated out. They produced the recombination products in the F3 generation when crossed back to the FLP-expressing plants. These observations may indicate that the efficiency of site-specific recombination is affected by the plant developmental stage, with site-specific recombination being more prevalent in developing embryos. The Cre::FLP fusion protein was also tested for excisions catalysed by Cre. Excisions were identified in the F1 plants and verified in the F2 plants by polymerase chain reaction and Southern blotting. Both components of the fusion protein (FLP and Cre) were functional and acted with similar efficiency. The crossing strategy proved to be suitable for the genetic engineering of maize using the FLP or Cre site-specific recombination system. [source] Leaf senescence is delayed in maize expressing the Agrobacterium IPT gene under the control of a novel maize senescence-enhanced promoterPLANT BIOTECHNOLOGY JOURNAL, Issue 2 2004Paul R. H. Robson Summary We have genetically modified maize plants to delay leaf senescence. A senescence-enhanced promoter from maize (PSEE1) was used to drive expression of the Agrobacterium cytokinin biosynthesis gene IPT in senescing leaf tissue. Three maize lines expressing IPT from PSEE1, Sg1, Sg2 and Sg3, were analysed in detail, representing mild, intermediate and extreme expression, respectively, of the delayed-senescence phenotype. Backcross populations segregating for the presence or absence of the PSEE1XbaIPTNOS transgene also simultaneously segregated for the senescence phenotype. At the time of ear leaf emergence, individuals of lines Sg1 and Sg2 segregating for the presence of the transgene carried about three fewer senescing leaves than control (transgene-minus) segregants, and IPT transcript levels were higher in leaves at incipient senescence than in young leaves. Leaves of transgenic Sg3 plants were significantly greener than controls and progressed directly from fully green to bleached and dead without an intervening yellowing phase. IPT transcript abundance in this line was not related to the initiation of senescence. Extended greenness was accompanied by a delay in the loss of photosynthetic capacity with leaf age. The delayed-senescence trait was associated with relatively minor changes in morphology and development. The phenotype was particularly emphasized in plants grown in low soil nitrogen. The reduced ability of the extreme transgenic line Sg3 to recycle internal nitrogen from senescing lower leaves accounted for significant chlorosis in emerging younger leaves when plants were grown in low nutrient conditions. This study demonstrates that the agronomically important delayed-senescence (,stay-green') trait can be engineered into a monocot crop, and is the first example outside Arabidopsis of senescence modification using a homologous senescence-enhanced promoter. [source] Leaf growth and turgor in growing cells of maize (Zea mays L.) respond to evaporative demand under moderate irrigation but not in water-saturated soilPLANT CELL & ENVIRONMENT, Issue 6 2006OUMAYA BOUCHABKÉ ABSTRACT To test whether the inhibition of leaf expansion by high evaporative demand is a result of hydraulic processes, we have followed both leaf elongation rate (LER) and cell turgor in leaves of maize plants either normally watered or in water-saturated soil in which hydraulic resistance at the soil,root interface was abolished. Cell turgor was measured in situ with a pressure probe in the elongating zone of the first and sixth leaves, and LERs of the same leaves were measured continuously with transducers or by following displacements of marks along the growing leaves. Both variables displayed spatial variations along the leaf and positively correlated within the elongating zone. Values peaked at mid-distance of this zone, where the response of turgor to evaporative demand was further dissected. High evaporative demand decreased both LER and turgor for at least 5 h, with dose-effect linear relations. This was observed in five genotypes with appreciable differences in turgor maintenance among genotypes. In contrast, the depressing effects of evaporative demand on both turgor and LER disappeared when the soil was saturated, thereby opposing a negligible resistance to water flow at the soil,root interface. These results suggest that the response of LER to evaporative demand has a hydraulic origin, enhanced by the resistance to water flux at the soil,root interface. They also suggest that turgor is not completely maintained under high evaporative demand, and may therefore contribute to the reductions in LER observed in non-saturated soils. [source] Seed transmission of maize downy mildew (Peronosclerospora sorghi) in NigeriaPLANT PATHOLOGY, Issue 5 2000V. O. Adenle In an area of Nigeria where downy mildew of maize is present, histological assessment of maize seed revealed the presence of mycelium and oospores of Peronosclerospora sorghi in the kernels. Seed transmission of downy mildew of maize was demonstrated when grain purchased at local markets gave mean seedling infection rates of 12·3% (untreated seeds) and 10·0% (in metalaxyl-treated seeds) within 7 days of emergence, after storage in a desiccator for 30 days. When untreated seeds taken from nubbin ears of systemically infected plants from four states in southern Nigeria were planted at 9 days (17,22% moisture content) and 27 days (9,22% moisture content) after harvest, 20·0% infected seedlings resulted in both trials. Seeds from Borno state in northern Nigeria had 26·6% systemic seedling infection after 9 months of storage at 11% moisture content. When seeds harvested from maize plants inoculated with P. sorghi through silks were examined histologically, hyphae of P. sorghi were observed mostly in the scutellum of the embryo. Transmission of disease to seedlings was observed when the silk-inoculated seeds (9% moisture content) were planted in pots in a greenhouse; however, no disease transmission was observed when such seeds were planted in the field. The epidemiological significance of seed transmission is discussed with particular reference to survival of inoculum and development of epidemics. Also noteworthy is the overall significance of seed transmission in Nigeria, where the major source of seed is that saved by farmers from their grain crop, occasionally supplemented by seed bought from the local market. [source] | ||||||||||||||||