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At least 199 records · Page 11Linked to original sources
PubMed1996

Molecular recognition of pathogen attack occurs inside of plant cells in plant disease resistance specified by the Arabidopsis genes RPS2 and RPM1.

The Arabidopsis thaliana disease resistance genes RPS2 and RPM1 belong to a class of plant disease resistance genes that encode proteins that contain an N-terminal tripartite nucleotide binding site (NBS) and a C-terminal tandem array of leucine-rich repeats. RPS2 and RPM1 confer resistance to strains of the bacterial phytopathogen Pseudomonas syringae carrying the avirulence genes avrRpt2 and avrB, respectively. In these gene-for-gene relationships, it has been proposed that pathogen avirulence genes generate specific ligands that are recognized by cognate receptors encoded by the corresponding plant resistance genes. To test this hypothesis, it is crucial to know the site of the potential molecular recognition. Mutational analysis of RPS2 protein and in vitro translation/translocation studies indicated that RPS2 protein is localized in the plant cytoplasm. To determine whether avirulence gene products themselves are the ligands for resistance proteins, we expressed the avrRpt2 and avrB genes directly in plant cell using a novel quantitative transient expression assay, and found that expression of avrRpt2 and avrB elicited a resistance response in plants carrying the corresponding resistance genes. This observation indicates that no bacterial factors other than the avirulence gene products are required for the specific resistance response as long as the avirulence gene products are correctly localized. We propose that molecular recognition of P. syringae in RPS2- and RPM1-specified resistance occurs inside of plant cells.

Amino Acid Sequence↗
PubMed2001

The plant pathogen Rhodococcus fascians colonizes the exterior and interior of the aerial parts of plants.

Rhodococcus fascians is a plant-pathogenic bacterium that causes malformations on aerial plant parts, whereby leafy galls occur at axillary meristems. The colonization behavior on Nicotiana tabacum and Arabidopsis thaliana plants was examined. Independent of the infection methods, R. fascians extensively colonized the plant surface where the bacteria were surrounded by a slime layer. R. fascians caused the collapse of epidermal cells and penetrated intercellularly into the plant tissues. The onset of symptom development preceded the extensive colonization of the interior. The meristematic regions induced by pathogenic strain D188 were surrounded by bacteria. The nonpathogenic strain, D188-5, colonized the exterior of the plant equally well, but the linear plasmid (pFiD188) seemed to be involved in the penetration efficiency and colonization of tobacco tissues.

Arabidopsis↗
PubMed2004

Production of 2-hydroxy-4-methoxybenzaldehyde in roots of tissue culture raised and acclimatized plants of Decalepis hamiltonii Wight & Arn., an endangered shrub endemic to Southern India and evaluation of its performance vis-a-vis plants from natural habitat.

Axillary buds obtained from field grown plants of D. hamiltonii were used to initiate multiple shoots on Murashige and Skoog's medium (MS) supplemented with 2 mg L(-1) 6-benzyl aminopurine (BA) and 0.5 mg L(-1) indole-3-acetic acid (IAA). Profuse rooting was achieved when the actively growing shoots were cultured on MS medium supplemented with 1.0 mg l(-1) indole-3-butyric acid (IBA). Regenerated plants were grown successfully in the plains, in contrast to wild growth in high altitudes and rocky crevices of hilly regions. Roots of different sizes from one-year-old tissue culture raised field grown plants had the same profile of 2-hydroxy-4-methoxybenzaldehyde as that of wild plants. A maximum of 0.14% and 0.12% 2-hydroxy-4-methoxybenzaldehyde was produced in roots of one year old tissue culture derived plants and greenhouse grown plants respectively.

Benzaldehydes↗
PubMed2001

Expression of a plant gene with sequence similarity to animal TGF-beta receptor interacting protein is regulated by brassinosteroids and required for normal plant development.

Brassinosteroids (BRs) regulate the expression of numerous genes associated with plant development, and require the activity of a Ser/Thr receptor kinase to realize their effects. In animals, the transforming growth factor-beta (TGF-beta) family of peptides acts via Ser/Thr receptor kinases to have a major impact on several pathways involved in animal development and adult homeostasis. TGF-beta receptor-interacting protein (TRIP-1) was previously shown by others to be an intracellular substrate of the TGF-beta type II receptor kinase which plays an important role in TGF-beta signaling. TRIP-1 is a WD-repeat protein that also has a dual role as an essential subunit of the eukaryotic translation initiation factor eIF3 in animals, yeast and plants, thereby revealing a putative link between a developmental signaling pathway and the control of protein translation. In yeast, expression of a TRIP-1 homolog has also been closely associated with cell proliferation and progression through the cell cycle. We report here the novel observation that transcript levels of TRIP-1 homologs in plants are regulated by BR treatment under a variety of conditions, and that transgenic plants expressing antisense TRIP-1 RNA exhibit a broad range of developmental defects, including some that resemble the phenotype of BR-deficient and -insensitive mutants. This correlative evidence suggests that a WD-domain protein with reported dual functions in vertebrates and fungi might mediate some of the molecular mechanisms underlying the regulation of plant growth and development by BRs.

Amino Acid Sequence↗
PubMed2005

[Expression of two plant agglutinin genes in transgenic tobacco plants].

A plant expression vector pBACG containing the DNA sequence coding for Amaranthus caudatus agglutinin (ACA) and a modified Glanthus nivalis agglutinin (GNA) gene was constructed. Leaf explants of Nicotiana tobacum cv. SRI were transformed with A. tumefaciens LBA4404 harbouring the above expression vector. Results from PCR and Southern blotting analysis showed that both the ACA and GNA gene were inserted into the genome of transformed tobacco plants. Western blottingting analysis of soluble protein isolated from transgenic plants showed that ACA and GNA were synthesized. The results from insect bioassay with peach aphids ( Myzus persicae) revealed that the transgenic plants of pBACG had acquired high resistance against peach aphids. The average aphid-inhibition rate reached up to 83.9% and 85.3% for transgenic plants (T0) and their selfed progenies (T1) respectively,indicating that the functions of these two genes were inheritable.

Agrobacterium tumefaciens↗
PubMed1987

Absence in monocotyledonous plants of the diffusible plant factors inducing T-DNA circularization and vir gene expression in Agrobacterium.

T-DNA circularization is one of the molecular events specifically induced in agrobacterial cells upon their infection of dicotyledonous plant cells. We developed a seedling co-cultivation procedure to determine whether or not monocotyledonous plants have the ability to induce T-DNA circularization and vir gene expression. Co-cultivation of Agrobacterium tumefaciens with seedlings of dicotyledonous plants showed that the circularization event takes place efficiently. The exudates and extracts of the seedlings also effectively induced T-DNA circularization and vir gene expression, indicating that dicotyledonous seedlings contain diffusible factors capable of inducing these molecular events. In contrast, neither T-DNA circularization nor vir gene expression was detectable when Agrobacterium was incubated with seedlings of monocotyledonous plants. Supplementing with acetosyringone, a known inducer of vir gene expression and T-DNA circularization, resulted in the induction of circularization during co-cultivation with moncotyledonous seedlings. These results indicate that the seedlings of monocotyledonous plants have no detectable amounts of diffusible inducers, unlike dicotyledonous seedlings. Therefore, it is unlikely that the vir genes are expressed in Agrobacterium inoculated in monocotyledonous plants. This may be one of the blocks in tumorigenesis of monocotyledonous plant by Agrobacterium.

DNA, Bacterial↗
PubMed1992

Monitoring and assessment of mercury pollution in the vicinity of a chloralkali plant. II Plant-availability, tissue-concentration and genotoxicity of mercury from agricultural soil contaminated with solid waste assessed in barley (Hordeum vulgare L.).

Barley (Hordeum vulgare L.) was used to assess plant-availability, tissue-concentration and genotoxicity of mercury from the solid waste deposits of a chloralkali plant. Seeds of H. vulgare, presoaked in distilled water, were allowed to germinate and grow on agricultural soil mixed with solid waste containing 2550+/-339 mg Hg kg(-1) at different proportions (0.75, 1.5, 2.5 and 5%). Plants raised from germinating seeds on uncontaminated agricultural soil served as controls. On day 7, germination counts and seedling heights were recorded. The concentration of mercury in soil, and plant tissue (dry weight) were determined at different stages of plant growth from day 7 till maturity and harvest. The availability of mercury from the soil was assessed by extracting mercury at a range of pH values (2-6) and by chemical methods. The embryonic shoots excised at 36 h of germination were subjected to cytological analysis to determine mitotic index and frequency of mitoses with chromosomal aberrations. The pollen mother cells from anthers of young M1-spikes were analysed to score meiotic aberrations. Subsequently, the pollen fertility and seed set were determined. Furthermore, M2-seedlings were analysed for chlorophyll-deficient mutations. The cytogenetic analysis revealed the effects of mercury on the mitotic and meiotic chromosomes which were significantly correlated with soil-mercury. The bioconcentration of mercury in aerial tissues decreased with the age of the plant. Roots, in particular, were found to concentrate most of the mercury taken up by the plant. At the time of harvest, the bioconcentration of mercury in straw was at a minimum. The accumulation of mercury in grain, which was significant, did not increase with the increase in concentration of mercury in soil but maintained a plateau, indicating a restriction of transport of mercury through the phloem. The unique advantage with the use of Hordeum assay is that, besides assessing the germline toxicity, the assay takes into account the possible contamination of the agricultural food-chain.

Journal Article↗
PubMed2006

Removal of bacteria by filtration in planted and non-planted sand columns.

In order to diminish hygienic hazards from pathogens, the elimination of pathogenic bacteria in a pre-treatment step is important for the use of domestic wastewater for irrigation purposes. Therefore, we analysed the removal of bacteria in laboratory-scale model sand filters simulating vertical flow systems of constructed wetlands (CW). Sand-filled glass columns were planted with Juncus effusus or Phragmites australis and non-planted columns were used as controls. Processes of bacteria removal such as adsorption, lysis, and the biotic effects caused by plants, protozoa, and Bdellovibrio were studied with E. coli as a model bacterium. E. coli suspensions (10(8) cellsml(-1)) were trickled on the columns by intermittent loading under non-water-saturated operation conditions. In non-planted and sterilized sand columns, an initial removal of cells was observed in the range as expected by the adsorption capacity of the sand columns. After loading of the sand with cells, an increasing reduction of the cell concentrations by 3-4 orders of magnitude in the effluent was registered up to volumetric loads of more than 548mll(-1) day(-1) (230mm day(-1)). In planted columns, no higher levels of removal were observed. Predation by protozoa, which were found in concentrations up to 10(4)ml(-1) in the effluent, is considered to be the main reason for the elimination. However, Bdellovibrio bacteriovorus was also found in plaque-forming units of about 10(4)g(-1) sand, suggesting that this bacteriovorous bacterium plays an additional role in the removal process. In a second series of experiments, domestic wastewater was applied and removal efficiencies up to four orders of magnitude of the cfu's of coliform bacteria, faecal streptococci, and salmonellae were observed. Considering the transpiration of the plants, higher removal efficiencies were found in the planted variants. Protozoa and Bdellovibrio were detected in the domestic wastewater in varying concentrations, suggesting that predation and lysis were the major removal mechanisms.

Bacteria↗
PubMed2001

Novel components of the plant cytoskeleton: a beginning to plant 'cytomics'

The bulk of our knowledge concerning the plant cytoskeleton has come primarily from the use of techniques and probes derived from animal research. However, in comparison with animal tissues, relatively few plant cytoskeleton proteins have been identified. We presume this is not because the plant cytoskeleton is really made up of such few proteins, but rather that only rarely have attempts been made to identify plant-specific cytoskeleton proteins, using plant-specific methods. Here we outline methods that we have developed both for the isolation and identification of novel cytoskeleton proteins as well as for the visualization of novel filamentous structures in plant cells, and we describe several novel cytoskeleton proteins and two novel cytoskeleton structures, 'nanofilaments' and 'nanotubules'. We postulate that use of such approaches will lead to a rapid expansion of our knowledge of the plant cytoskeleton.

Journal Article↗
PubMed2003

Monitoring the effects of atmospheric ethylene near polyethylene manufacturing plants with two sensitive plant species.

Data of a multi-year (1977-1983) biomonitoring programme with marigold and petunia around polyethylene manufacturing plants was analysed to assess plant responses to atmospheric ethylene and to determine the area at risk for the phytotoxic effects of this pollutant. In both species, flower formation and growth were severely reduced close to the emission sources and plant performance improved with increasing distance. Plants exposed near the border of the research area had more flowers than the unexposed control while their growth was normal. Measurements of ethylene concentrations at a border site revealed that the growing season mean was 61.5 g m(-3) in 1982 and 15.6 g m(-3) in 1983. In terms of number of flowers, petunia was more sensitive than marigold and adverse effects were observed within ca. 400 m distance from the sources for marigold and within ca. 460 m for petunia. The area at risk (ca. 870 m) for ethylene-induced growth reduction was also limited to the industrial zone. Plants were more sensitive to ethylene in terms of growth reduction than in terms of inhibition of flowering. In the Netherlands, maximum permissible levels of ethylene are currently based on information from laboratory and greenhouse studies. Our results indicate that these levels are rather conservative in protecting field-grown plants against ethylene-induced injury near polyethylene manufacturing plants.

Air Pollutants↗
PubMed2002

Plant biotechnology--genetic engineering to enhance plant salt tolerance.

Plants not only provide food to humans and animals, but also provide a large number of non-food products of industrial and chemical importance. Moreover, they have the ability to purify the air, soil and water on the earth. Various trials to genetically improve the potential of plants are actively in progress. Salt-tolerance would be an especially important ability to bestow upon plants for agricultural and industrial purposes, because high salinity conditions are ubiquitous on earth and represent major barriers to growth. Enhancement of resistance against both hyper-osmotic stress and Na+ toxity is necessary for successful molecular breeding of salt tolerant plants. Introduction of genes for osmolyte bio-synthesis is useful to increase hyperosmotic tolerance of plant cells. It is introduced in this review that genetically engineered ectoine synthesis results in increased hyperosmotic tolerance of tobacco cells. High concentrations of Na+ reduce cellular activity by interfering with vital Na+-sensitive enzymes and by affecting K+ transport. Understanding the regulation of K+ and Na+ homeostasis is thus indispensable for enhancement of plant Na+ tolerance. My research group is investigating the Na+ efflux activity of the yeast Na+-ATPase (Ena1) when installed in the plasma membrane of plant cells, and the rice K+-Na+ co-transporters (HKT) that contribute to the regulation of K+ and Na+ uptake in root cells.

Journal Article↗
PubMed2001

A domain unique to plant RanGAP is responsible for its targeting to the plant nuclear rim.

Ran is a small signaling GTPase that is involved in nucleocytoplasmic transport. Two additional functions of animal Ran in the formation of spindle asters and the reassembly of the nuclear envelope in mitotic cells have been recently reported. In contrast to Ras or Rho, Ran is not associated with membranes. Instead, the spatial sequestering of its accessory proteins, the Ran GTPase-activating protein RanGAP and the nucleotide exchange factor RCC1, appears to define the local concentration of RanGTP vs. RanGDP involved in signaling. Mammalian RanGAP is bound to the nuclear pore by a mechanism involving the attachment of small ubiquitin-related modifier protein (SUMO) to its C terminus and the subsequent binding of the SUMOylated domain to the nucleoporin Nup358. Here we show that plant RanGAP utilizes a different mechanism for nuclear envelope association, involving a novel targeting domain that appears to be unique to plants. The N-terminal WPP domain is highly conserved among plant RanGAPs and the small, plant-specific nuclear envelope-associated protein MAF1, but not present in yeast or animal RanGAP. Confocal laser scanning microscopy of green fluorescent protein (GFP) fusion proteins showed that it is necessary for RanGAP targeting and sufficient to target the heterologous protein GFP to the plant nuclear rim. The highly conserved tryptophan and proline residues of the WPP motif are necessary for its function. The 110-aa WPP domain is the first nuclear-envelope targeting domain identified in plants. Its fundamental difference to its mammalian counterpart implies that different mechanisms have evolved in plants and animals to anchor RanGAP at the nuclear surface.

Amino Acid Sequence↗
PubMed2004

Tomato psyllid behavioral responses to tomato plant lines and interactions of plant lines with insecticides.

Adult tomato psyllid, Bactericerca (Paratrioza) cockerelli (Sulc) (Homoptera: Psyllidae), behavioral responses were evaluated for five tomato plant lines and for the interactions of insecticides with four commercial cultivars. Plant lines tested included the commercial 'Shady Lady', 'Yellow Pear', '7718 VFN', 'QualiT 21', and the plant introduction line PI 134417. Insecticides included a kaolin particle film, pymetrozine, pyriproxyfen, spinosad, and imidacloprid. Psyllids spent significantly more time feeding on 'Yellow Pear' than all other plant lines except '7718 VFN'. In comparisons among plant lines, psyllids exposed to the wild accession PI 1.34417 showed a 98% reduction in feeding, a significant increase in jumping behavior, and a significant tendency to abandon the leaves, thereby demonstrating repellency, not just an antixenosis response. Interactions between plant lines and insecticides influenced behavioral responses. All insecticides tested significantly reduced feeding durations on all cultivars except the preferred 'Yellow Pear'. However, nonfeeding activities such as walking, probing, resting, and jumping varied substantially with chemical and cultivar combination. The behavior assay results offered insight into host resistance mechanisms, provided a useful technique for measuring effects of interaction of plant lines with insecticides, and generated information for selecting insecticides for specific cultivars used in integrated pest management program for the tomato psyllid.

Animals↗
PubMed1977

Floral induction of vegetative plants supplied a purified fraction of deoxyribonucleic Acid from stems of flowering plants.

It has been found that floral induced stems of flowering tobacco (Nicotiana tabacum cv. Wis. 38) plants contain large amounts of rapidly renaturing DNA, whereas noninduced stems of vegetative plants contain only small amounts. In addition, it has been shown that the striking qualitative difference in DNA between stems of flowering and vegetative plants mimics the over-all quantitative difference in DNA content (on a fresh weight basis). Therefore, the extra DNA in stems of flowering plants seems, at least in part, to represent preferential synthesis of rapidly renaturing DNA.Rapidly renatured DNA (flowering plants) has been purified (cesium chloride gradients) from heated-cooled DNA solution and under noninductive conditions has been tested for floral activity. It has been found that when rapidly renatured DNA in buffer solution is supplied to axillary vegetative buds of vegetative plants and then the axillary buds are defoliated every 4th day for 12 days, the treated buds change into flower buds. On the other hand, control axillary buds supplied buffer solution alone remain vegetative.In stem segments from flowering plants, the concept, discussed in previous reports, that indole-3-acetic acid may modify in vitro bud expression by directly affecting DNA synthesis has been reviewed. On the basis of this report, the concept is elaborated by proposing here that indole-3-acetic acid may act partially in bud expression by directly suppressing synthesis of rapidly renaturing DNA.

Journal Article↗
PubMed2005

Plant-derived mouse IgG monoclonal antibody fused to KDEL endoplasmic reticulum-retention signal is N-glycosylated homogeneously throughout the plant with mostly high-mannose-type N-glycans.

Plants are potential hosts for the expression of recombinant glycoproteins intended for therapeutic purposes. However, N-glycans of mammalian glycoproteins produced in transgenic plants differ from their natural counterparts. The use of the endoplasmic reticulum (ER)-retention signal has been proposed to restrict glycosylation of plantibodies to only high-mannose-type N-glycans. Furthermore, little is known about the influence of plant development and growth conditions on N-linked glycosylation. Here, we report a detailed N-glycosylation profiling study of CB.Hep1, a mouse IgG2b monoclonal antibody (mAb) against hepatitis B surface antigen (HBsAg) currently expressed in tobacco plants (Nicotiana tabacum L.). The KDEL ER-retention signal was fused to the C-terminal of both light and heavy chains. The structures of the N-linked glycans of this mAb produced in transgenic tobacco plants at various growth stages were analysed by high-performance liquid chromatography (HPLC) profiling techniques and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and compared with those of murine origin. The high-mannose-type oligosaccharides accounted for more than 80% of the total N-glycans, with Man7GlcNAc2 being the most abundant species. Some complex N-glycans bearing xylose and small amounts of oligosaccharides with both xylose and fucose were identified. No appreciable differences were detected when comparing glycosylation at different leaf ages, e.g. from seedling leaves up to 8 weeks old and top or basal leaves of mature plants, or between leaves, stems and whole plants. A strict retention of glycoproteins to ER by the use of the tetrapeptide KDEL was not sufficient, even though the majority of the resulting N-glycosylation was of the high-mannose type. It is highly likely to be dependent on other factors, which are most probably protein specific.

Journal Article↗
PubMed2006

Symbiotic bacteria as a determinant of plant community structure and plant productivity in dune grassland.

Symbiotic interactions are thought to play a key role in ecosystems. Empirical evidence for the impact of symbiotic bacteria on plant communities is, however, extremely scarce because of experimental constraints. Here, in three complementary experiments, we show that nitrogen-fixing rhizobia bacteria act as a determinant of plant community structure and diversity. Grassland microcosms inoculated with a mixture of rhizobia had a higher above-ground plant productivity (+35%), contained more nitrogen (+85%) and had significant higher community evenness (+34%) than control microcosms without rhizobia. Moreover, three of the four studied legume species required rhizobia to successfully coexist with other plant species. In contrast, the growth and survival of three grass and five forb species were not affected by the presence or absence of rhizobia. Finally, our results also showed that the legume species largely relied on symbiotically fixed nitrogen, both in the field and in the microcosms. This indicates that results in the microcosms are indicative for processes occurring in the field. It is concluded that symbiotic interactions between plants and prokaryotes can contribute to plant productivity, plant community structure and acquisition of limiting resources in legume-rich grassland communities.

Asteraceae↗
PubMed2006

Reliable DNA ploidy determination in dehydrated tissues of vascular plants by DAPI flow cytometry--new prospects for plant research.

BACKGROUND: Only fresh plant material is generally used for rapid DNA ploidy estimation by flow cytometry (FCM). This requirement, however, substantially limits convenient FCM application in plant biosystematics, population biology, and ecology. As desiccation is a routine way for sample preservation in field botany, potential utilization of dehydrated tissues of vascular plants in FCM research was examined. METHODS: Standard DAPI protocol was employed to evaluate the performance of 60 air-dried species, spanning more than 100-fold range of nuclear DNA amounts. Multiploid Vaccinium subg. Oxycoccus was selected as model taxon for detailed investigation and cytotype comparison. RESULTS: A majority of analyzed plants yielded distinct peaks with reasonable coefficients of variation after several months of storage at room temperature. Fluorescence intensity of nuclei isolated from desiccated tissues was highly comparable with that for fresh material, allowing reliable DNA ploidy estimation. Deep-freezer preservation substantially extended Vaccinium samples lifetime (at least to 3 years) and maintained high histogram resolution. CONCLUSIONS: The introduced approach eliminates the need for fresh material in many vascular plants and thus opens new prospects for plant FCM. Convenient cytotype investigation in field research and retrospective ploidy determination in already herbarized samples are among the principal advantages.

DNA, Plant↗
PubMed2004

Antimalarial activity of Bidens pilosa L. (Asteraceae) ethanol extracts from wild plants collected in various localities or plants cultivated in humus soil.

Bidens pilosa (Asteraceae), a medicinal plant used worldwide, has antimalarial activity as shown in previous work. This study tested ethanol extracts from wild plants collected in three different regions of Brazil and from plants cultivated in various soil conditions. The extracts were active in mice infected with P. berghei: doses of < or =500 mg/kg administered by oral route reduced malaria parasitaemia and mouse mortality; higher doses were found to be less effective. Tested in vitro against three P. falciparum isolates, two chloroquine resistant and one mefloquine resistant, the plants cultivated under standard conditions, and in humus enriched soil, were active; but the wild plants were the most active. Analysis using thin layer chromatography demonstrated the presence of flavonoids (compounds considered responsible for the antimalarial activity) in all plants tested, even though at different profiles. Because B. pilosa is proven to be active against P. falciparum drug-resistant parasites in vitro, and in rodent malaria in vivo, it is a good candidate for pre-clinical tests as a phytotherapeutic agent or for chemical isolation of the active compounds with the aim of finding new antimalarial drugs.

Animals↗