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At least 343 records · Page 19Linked to original sources
PubMed1996

[Construction and analysis of transgenic plants of Nicotiana tabacum L. expressing a bacterial gene for beta-1,3-glucanase. II. Transgenic tobacco plants expressing the bacterial beta-glucanase gene from Clostridium thermocellum,--a model for studying the differential expression of stress response-related genes].

The modified hybrid beta-1,3-glucanase gene (glc) of Clostridium thermocellum was expressed in tobacco Nicotiana tabacum. The glc gene was cloned into two plasmids, pC27-glc and pC29-glc, in which its expression was controlled by the TR2' promoter of the 2' gene of T-DNA and the rbcS promoter of Arabidopsis, respectively. These constructions were used for transformation of agrobacteria followed by transfer into plants. In transformed plants, each plasmid caused a high level of activity of thermostable bacterial glucanase not observed in reference plants. The plants obtained were used to study activation of some defense-related genes induced by their interaction with either tobacco mosaic virus (TMV) or a pathogenic fungus.

Cloning, Molecular↗
PubMed1996

Plant hormones and plant virus diseases. The auxins.

Systemic virus infection impairs the steady state of auxin hormone in plant with consequent morphogenetic alterations. Most reports indicate a reduction of auxin activity in diseased plants, generally associated with stunting, but a substantial increase in auxin activity has sometimes been observed in cases of severe symptomatology. Treatments of virus-diseased plants with exogenous auxins may inhibit virus replication and reduce symptom severity, although results have been obtained by empirical application and must therefore be considered with caution. There is no information on how virus infection alters auxin metabolism or how this alteration affects both plant growth and development. The considerable progress reached in auxin biochemistry now allows more accurate re-investigations of this important relationship.

Indoleacetic Acids↗
PubMed1997

[Transfer of bacterial genes for proline synthesis in plants and their expression by various plant promotors].

Accumulation of free proline (Pro) by bacteria and plants serves as a mechanism protecting these organisms from abiotic stress. We introduced two E. coli genes, proBosm, encoding a mutant variant of the first enzyme of the Pro biosynthetic pathway, gamma-glutamyl kinase, and proA, encoding the second enzyme of the Pro pathway, glutamyl-gamma-semialdehyde dehydrogenase, into tobacco plants. The spontaneous proBosm mutation was selected for Pro overproduction and mapped to the N-terminus of a polypeptide chain; it was found to result from one amino-acid substitution. Two E. coli genes were simultaneously introduced into tobacco plants, each under the control of a strong constitutive CaMV 35S promoter, which contained a duplicated sequence of enhancer, or the root-specific Pmas promoter sequence. Transgenic plants were characterized by Pro overproduction, increased resistance to L-azetidine-2-carboxylic acid (a toxic analog of Pro), and tolerance to salt stress.

Agrobacterium tumefaciens↗
PubMed2000

Plant Species and Plant Incubation Conditions Influence Variability in Epiphytic Bacterial Population Size.

The influences of plant species and plant incubation conditions on the variability in bacterial population sizes among leaves were investigated in field and growth chamber studies. Pseudomonas syringae strains TLP2 and Cit7 were inoculated onto plants and population sizes were measured at intervals after inoculation. Total bacterial population sizes were also assessed in field studies. Levels of leaf-to-leaf variability in both P. syringae population size and bacterial community size differed significantly among plant species. For all plant species, variability among leaves in population sizes of inoculated bacteria was consistently greater than the leaf-to-leaf variability in numbers of total bacteria. Considering levels of variability in population size immediately prior to and following incubation under either wet or dry physical conditions, leaf-to-leaf variability in the population sizes of inoculated P. syringae strains increased significantly following incubation under dry, but not under wet, conditions. Measurements of leaf-to-leaf variability immediately prior to and following incubation were positively correlated regardless of whether the incubation was under wet or dry conditions, though the correlation was greater following dry incubation. These data provide insight into the biological and physical factors that may be important in generating variability in bacterial population sizes among leaves, and they have important implications for the design of appropriate strategies for sampling leaf surface microbial populations. </hea

Journal Article↗
PubMed2002

Elicitor-like effects of low-energy ultrasound on plant (Panax ginseng) cells: induction of plant defense responses and secondary metabolite production.

In this work we examined the elicitor-like effects of low-energy ultrasound (US) on plant cells with respect to the induction of plant defense responses and secondary metabolite production. Panax ginseng cells in suspension culture were exposed to US (power <or=0.1 W/cm(3) at 38.5 kHz fixed frequency) for short periods of time (30 s-6 min). Two early events in plant defense metabolism and signal transduction pathways, the increased cross-membrane ion fluxes (Ca(2+) influx and K(+) efflux/H(+) influx) and the production of active oxygen species (AOS), were detected in sonicated cultures within 2 min after US exposure. These responses could be induced with small doses of US energy, 0.6-0.8 J/cm(3), and enhanced by increasing US energy within a non-inhibitory range. US treatment stimulated the synthesis of useful secondary metabolites, saponins of ginseng cells, without causing any net loss of the biomass yield of ginseng cell cultures. These results suggest that US can act as a potent abiotic elicitor to induce the defense responses of plant cells and to stimulate secondary metabolite production in plant cell cultures.

Cell Membrane↗
PubMed1994

Plant growth and gas balance in a plant and mushroom cultivation system.

In order to obtain basic data for construction of a plant cultivation system incorporating a mushroom cultivation subsystem in the CELSS, plant growth and atmospheric CO2 balance in the system were investigated. The plant growth was promoted by a high level of CO2 which resulted from the respiration of the mushroom mycelium in the system. The atmospheric CO2 concentration inside the system changed significantly due to the slight change in the net photosynthetic rate of plants and/or the respiration rate of the mushroom when the plant cultivation system combined directly with the mushroom cultivation subsystem.

Basidiomycota↗
PubMed2006

Revisiting the plant hyperaccumulation criteria to rare plants and earth abundant elements.

The several established criteria to define a hyperaccumulator plant were applied to a rare and endangered species, Plantago almogravensis, and to the 3rd most abundant element in the earth crust, Al. Using the most common criteria, P. almogravensis undoubtedly is an Al hyperaccumulator plant. If the recent proposed requirements were considered, most of them matching those for a plant to be used in phytoextraction, it can only be considered an unusual accumulator of Al. A discussion is made concerning the several criteria of a hyperaccumulator plant in order to include rare and endemic ones and abundant elements. In ecological terms, the enrichment in Al and Fe observed may account for the differences in the vegetation pattern. Due to the rarity and endangered nature of this plant, the contribution of this work is also relevant for the ecological understanding and the development of conservation options of this endemic species.

Adsorption↗
PubMed2004

Temperature step changes: a novel approach to control biofilms of Streptococcus thermophilus in a pilot plant-scale cheese-milk pasteurisation plant.

A pilot plant-scale cheese-milk pasteurisation plant was designed and constructed to study the development of biofilms of Streptococcus thermophilus during pasteurisation of milk, and to investigate methods for preventing this growth from occurring. Under base run conditions, S. thermophilus grew on surfaces in the cool-down sections of the pilot plant, between 50 and 35 degrees C (bulk milk temperature), and could be detected in the product stream after 8-10 h production, reaching levels of 10(6) CFU ml-1 after 16 h. Thermoduric bacteria also grew in the heating sections of the pilot plant, although to a lesser extent, as did non-thermoduric bacteria that originated in the raw milk. The novel application of temperature step changes, implemented periodically to the growth region of S. thermophilus, successfully controlled the development of biofilms of these organisms. The growth of bacteria on the heating side of the pilot plant was also prevented by the implementation of these same step changes. The optimum step change conditions required to achieve a 20-h production run without detectable growth of S. thermophilus comprised a step change to 55 degrees C, applied for 10 min, with a 60-min interval between step changes.

Animals↗
PubMed2004

Purification of a plant cell wall fibronectin-like adhesion protein involved in plant response to salt stress.

The structural role of extracellular-matrix (ECM) has been recognized in both plants and animals as a support and anchorage-inducing cell behavior. Unlike the animal ECM proteins, the proteins that have been identified in plant ECM have not yet been purified from whole plants and cell wall. As several immunological data indicate the presence of animal ECM-like proteins in plants cell wall, especially under salt stress or water deficit, we propose a protocol to purify a fibronectin-like protein from the cell wall of epicotyls of young germinating peas. The process consists of a combination of gelatin and heparin affinity chromatography, close to the classical one used for human blood plasma fibronectin purification. Proteins with affinity for gelatin and heparin, immunologically related to human fibronectin, are found in the cell wall of epicotyls grown under salt stress or not. Total amount of purified proteins is 3-4 times more enriched in salt stressed epicotyls. SDS-PAGE and Western blot with antibodies directed against human blood plasma fibronectin give evidence that the cell wall proteins purified by gelatin/heparin affinity chromatography are closely related to human fibronectin. The present protocol leads us to purify 17 (control) or 65 (salt stress) micrograms of protein per g of fresh starting material. Our results suggest that plant cell wall proteins can provide better anchorage of the cell to its cell-wall during salt stress or water deficit and could be considered not only as cell adhesion but also as signaling molecules.

Cell Adhesion↗
PubMed2006

Characterization of plant phenotypes associated with loss-of-function of AtCNGC1, a plant cyclic nucleotide gated cation channel.

Of the 57 cation channel genes in the Arabidopsis genome, over a third encode cyclic nucleotide gated cation channels (CNGCs). CNGCs are ion channels regulated by cytosolic signaling molecules (cyclic nucleotides, calmodulin, and Ca(2+)), and which conduct Ca(2+) as well as K(+) and in some cases Na(+). Little is currently known about the role CNGCs may play in plant growth and development. Here, we examined the hypothesis that an Arabidopsis thaliana genotype containing a null mutation in one of the CGNC genes (AtCNGC1) would display cation uptake-related growth phenotype differences from wild type (WT) plants. We determined that AtCNGC1 protein is primarily expressed in the roots of Arabidopsis seedlings. Seedlings lacking this protein had slightly (6-22%) lower shoot Ca(2+) than WT plants. Primary roots of Atcngc1 mutant seedlings grew faster than roots of WT plants, and had larger angles of gravicurvature and less nitric oxide generation upon gravistimulation. We conclude that channels formed (at least in part) by AtCNGC1 contribute (along with other channels) to Ca(2+) uptake into plants, and that Ca(2+) uptake into roots through AtCNGC1 affects some aspects of growth in the primary root of Arabidopsis seedlings.

Arabidopsis↗
PubMed2002

Non-invasive determination of plant-associated bacteria in the phyllosphere of plants.

Epiphytic living Pseudomonas strains isolated from different Malus domestica cultivars were transformed with two reporter genes [green fluorescent protein (gfp) and luciferase (luxAB)]. The establishment and distribution of these bacteria on sterile, in vitro-propagated, and thus genetically identical, Malus domestica plants were continuously analysed with a cooled, back-illuminated, charge-coupled-device (CCD) camera system. The combination of the assessment of bioluminescence and the use of a CCD camera offer an intriguing method to study, non-invasively and in real time, plant-microbe interactions as well as the colonization of the phyllosphere by microorganisms. Here we report on the applicability and sensitivity of the method with the goal to investigate quantitatively the interaction of symbiotic and pathogenic microorganisms with the corresponding host plant. It will be shown that the three bacterial isolates of the genus Pseudomonas studied, differ considerably with respect to their establishment on the host plants. It will also be shown that the chosen host apple variety has an impact on the activity of the bacterial cultivars. Analysis by a laser scanning fluorescence microscope provides the first evidence for the mode by which the epiphytic microorganisms interact with the plant.

Luminescent Measurements↗
PubMed2003

Examination of plant performance and filter ripening with particle counters at full-scale water treatment plants.

Filter performance has traditionally been assessed using turbidity as the main water quality parameter. However interest in process optimization and the ability to accurately monitor filtration and particle removal has led to particle counting becoming increasingly more popular. The objective of this research was to evaluate filtration performance and filter ripening at four full-scale water treatment plants. Most of the plants investigated in this study were capable of achieving 2 log total particle removal as well as an effluent turbidity of 0.1 NTU. In some cases 2 log removal was achieved in the lower particle size ranges of 2-5 and 5-10 microm. Log removals in this study compare particle counts in the filtered and raw water. For water treatment plants that do not filter to waste, the ripening period following a filter backwash represents a time where the plant may be most vulnerable to breakthrough of waterborne pathogens. For the plants studied, the ripening period which was defined as the time required to reach peak particle removal and a turbidity of 0.1 NTU, were very similar in duration. The ripening period generally lasted for one hour after the backwash event had been completed. Because the times to reach 2 log total particle removal and 0.1 NTU are similar, the practice of using 0.1 NTU turbidity as a measure of filter ripening may be a useful benchmark for utilities that do not have particle counters.

Environmental Monitoring↗
PubMed1988

Planting stress in newly planted jack pine and white spruce. 2. Changes in tissue water potential components.

Water relations of bare-root jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) planted in a greenhouse and on a boreal cut-over site were examined during the first growing season. In field-planted trees, maximum stomatal conductances (g(wv)) were initially low (< 0.10 cm s(-1)). Base and minimum xylem pressure potentials (Psi(x(base)) and Psi(x(min))) were less than -1.5 and -1.7 MPa for jack pine and -2.0 and -2.6 MPa for white spruce, respectively. During the growing season, maximum g(wv) increased in both species to around 0.2 cm s(-1). Base and minimum xylem pressure potentials also increased in both species to around -0.5 and -1.0 MPa in jack pine and -1.0 and -1.5 MPa in white spruce, respectively. Minimum xylem pressure potentials in white spruce fell below the turgor loss point during the first half of the growing season. Osmotic potential at the turgor loss point Psi(pi(TLP)) decreased after field planting to around -2.7 and -2.3 MPa in jack pine and white spruce, respectively. In the greenhouse, minimum values of Psi(pi(TLP)) were -2.2 and -2.3 MPa in jack pine and white spruce, respectively. Maximum bulk modulus of elasticity was greater in white spruce and underwent greater seasonal change than in jack pine. Relative water content (RWC) at turgor loss ranged between 71 and 74% in jack pine and 80 and 87% in white spruce. Available turgor (T(avail)), defined as the integral of turgor over the range of RWC between Psi(x(base)) and xylem pressure potential at the turgor loss point, was similar in jack pine and white spruce just after field planting. For the rest of the growing season, however, T(avail) in jack pine was two to three times that in white spruce. Diurnal turgor (T(diurnal)), defined as the integral of turgor over the range of RWC between Psi(x(base)) and Psi(x(min)), as a percent of T(avail) was higher in field-planted white spruce than jack pine until the end of the season. Dynamics of tissue water potential components are discussed in relation to plantation establishment.

Journal Article↗
PubMed1997

Transgenic Tobacco Plants Expressing Pea Chloroplast Nmdh cDNA in Sense and Antisense Orientation (Effects on NADP-Malate Dehydrogenase Level, Stability of Transformants, and Plant Growth).

A full-length cDNA encoding light-activated chloroplast NADP-malate dehydrogenase (NADP-MDH) (EC 1.1.1.82) from pea (Pisum sativum L.) was introduced in the sense and antisense orientation into tobacco (Nicotiana tabacum L.). Transgenic plants with decreased or increased expression levels were obtained. Because of substantial age-dependent differences in individual leaves of a single plant, standardization of NADP-MDH levels was required first. Then, extent and stability of over- or under-expression of Nmdh, the gene encoding NADP-MDH, was characterized in the various transformants. Frequently, cosuppression effects were observed, indicating sufficient homology between the endogenous tobacco and the heterologous pea gene. Analysis of the T1 and T2 progeny of a series of independent transgenic lines revealed that NADP-MDH capacity ranged between 10% and [greater than or equal to]10-fold compared with the wild type. Under ambient conditions whole-plant development, growth period, and fertility were unaffected by NADP-MDH reduction to 20% of the wild-type level; below this threshold plant growth was retarded. A positive growth effect was registered in young plants with stably enhanced NADP-MDH levels within a defined developmental window.

Journal Article↗
PubMed1979

Cell Surfaces in Plant-Microorganism Interactions: I. A Structural Investigation of Cell Wall Hydroxyproline-rich Glycoproteins Which Accumulate in Fungus-infected Plants.

Infection of muskmelon Cucumis melo seedlings by the fungus Colletotrichum lagenarium causes a 10-fold increase in the amount of cell wall hydroxyproline-rich glycoprotein. Evidence for this increase was provided by studying two specific markers of this glycoprotein, namely hydroxyproline and glycosylated serine. The lability of the O-glycosidic linkage of wall-bound glycosylated serine in the presence of hydrazine, was used to determine the amount of serine which is glycosylated.A large increase in the hydroxyproline content of infected plants is shown, but the ratios of glycosylated serine to hydroxyproline are similar in healthy and infected plants. As far as these markers are concerned, the hydroxyproline-rich glycoproteins secreted into the wall as a result of the disease are similar to those of healthy plants. In addition, the extent of glycosylation of the wall serine, in both healthy and infected plants, decreases as the plant ages.Serine- and hydroxyproline-rich (glyco)peptides were also isolated after trypsinolysis of the wall. These (glyco)peptides include the galactosyl-containing pentapeptide, serine-hydroxyproline(4). This pentapeptide is characteristic of cell wall protein.

Journal Article↗
PubMed2005

Polar localizing class V myosin chitin synthases are essential during early plant infection in the plant pathogenic fungus Ustilago maydis.

Fungal chitin synthases (CHSs) form fibers of the cell wall and are crucial for substrate invasion and pathogenicity. Filamentous fungi contain up to 10 CHSs, which might reflect redundant functions or the complex biology of these fungi. Here, we investigate the complete repertoire of eight CHSs in the dimorphic plant pathogen Ustilago maydis. We demonstrate that all CHSs are expressed in yeast cells and hyphae. Green fluorescent protein (GFP) fusions to all CHSs localize to septa, whereas Chs5-GFP, Chs6-GFP, Chs7-yellow fluorescent protein (YFP), and Myosin chitin synthase1 (Mcs1)-YFP were found at growth regions of yeast-like cells and hyphae, indicating that they participate in tip growth. However, only the class IV CHS genes chs7 and chs5 are crucial for shaping yeast cells and hyphae ex planta. Although most CHS mutants were attenuated in plant pathogenicity, Deltachs6, Deltachs7, and Deltamcs1 mutants were drastically reduced in virulence. Deltamcs1 showed no morphological defects in hyphae, but Mcs1 became essential during invasion of the plant epidermis. Deltamcs1 hyphae entered the plant but immediately lost growth polarity and formed large aggregates of spherical cells. Our data show that the polar class IV CHSs are essential for morphogenesis ex planta, whereas the class V myosin-CHS is essential during plant infection.

Aminoglycosides↗
PubMed2005

Arabidopsis AtSPL14, a plant-specific SBP-domain transcription factor, participates in plant development and sensitivity to fumonisin B1.

The recessive Arabidopsis thalianafumonisin B1-resistant (fbr6) mutant was identified by its ability to survive in the presence of a programmed cell death (PCD)-inducing fungal toxin FB1. The fbr6 mutant also displays altered plant architecture in the absence of FB1, most notably elongated petioles and enhanced leaf margin serration. These phenotypes are a result of a T-DNA insertion in the SQUAMOSA promoter binding protein (SBP) domain gene, AtSPL14. AtSPL14 encodes a plant-specific protein with features characteristic of a transcriptional regulator, including a nuclear localization signal sequence, a plant-specific DNA binding domain (the SBP box), and a protein interaction motif (ankyrin repeats). A transiently expressed fusion of the AtSPL14 protein to green fluorescent protein is directed to the plant nucleus. DNA sequences immediately upstream of the translation start site direct expression of the beta-glucuronidase reporter gene primarily in the vascular tissues, consistent with the phenotypes of the fbr6 mutant. AtSPL14 activates transcription in yeast, with a transactivation domain residing within the N-terminal region of the protein. Recombinant AtSPL14 protein binds A. thaliana genomic DNA in vitro in the absence of other proteins. These results indicate that FBR6/SPL14 functions as a transcriptional regulator that plays a role not only in sensitivity to FB1, but also in the development of normal plant architecture.

Arabidopsis↗
PubMed1980

Mortality of workers on an isopropyl alcohol plant and two MEK dewaxing plants.

An historical prospective study was undertaken of 262 men who had worked on an isopropyl alcohol plant and 446 men who had worked on two MEK dewaxing plants. All of the former have been traced, and only one man from the latter group was lost to follow-up. These studies linked occupational records with cause of death data for those who had died; the average follow-up was 15.5 years for the IPA plant workers and 13.9 years for those on the MEK dewaxing plants. For the IPA workers the observed deaths (26) were slightly above the expected (23.6), and there was a non-significant excess of deaths from neoplasms (0 = 9, E = 6.19). One person died from nasal cancer (E = 0.02, p = 0.017); though based on small numbers this finding is unlikely to be due to chance and agrees with the original hazard. For those who had worked on the MEK dewaxing plants the observed deaths (46) were below the expected (55.51) and there was also a slight deficiency of deaths from neoplasms (0 = 13, E = 14.26). When the seven sites of malignancy, which had been examined in a recent American study, were compared there were significantly more deaths from buccal cavity and pharynx cancers (0 = 2; E = 0.13; p = 0.008) and significantly fewer from lung cancer (0 = 1; E = 6.02; p less than 0.045). After reviewing the American and present results, it was concluded that there is no clear evidence of a cancer hazard in these workers, though further follow-up of larger numbers is necessary for a more precise estimate of the confidence limits of these findings.

1-Propanol↗