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At least 163 records · Page 9Linked to original sources
PubMed2005

Local infiltration of high- and low-molecular-weight RNA from silenced sunflower (Helianthus annuus L.) plants triggers post-transcriptional gene silencing in non-silenced plants.

Using grafting procedures, we have characterized post-transcriptional gene silencing (PTGS) in transgenic sunflower expressing beta-glucuronidase (GUS) activity. Silencing was observed as early as 2 weeks after grafting of non-silenced scions on to silenced rootstock. Transmission of the systemic signal occurs solely from stock to scion, is independent of the physiological age of the rootstock and is not heritable. Furthermore, we report, for the first time in plants, an easy and low-cost method of activating RNA silencing by infiltration of purified RNA from silenced plants. Local application of total RNA derived from silenced sunflower plants to leaves of non-silenced plants induces PTGS in newly developed leaves above the point of infiltration, as shown by reduced GUS activity and mRNA levels. Silenced plants contain 21-23-nucleotide RNAs hybridizing to transgene target sequences, in contrast with leaves of non-silenced plants. However, de novo production of GUS-specific short RNA in non-silenced plants can be activated by leaf infiltration of low-molecular-weight RNAs isolated from leaves of silenced plants. Significant levels were detected as early as 2 weeks after infiltration, peaked at 3 weeks and declined 5 weeks after infiltration. Our results provide evidence that RNA infiltration in sunflower induces transient silencing and is not transmitted to offspring. This approach could be of major use in dissecting the mechanisms involved in PTGS.

Journal Article↗
PubMedDate not supplied

Variations of tetrahydrocannabinol content in cannabis plants to distinguish the fibre-type from drug-type plants.

There are many different species of cannabis plants, but their psychoactive properties mainly depend on the concentration of tetrahydrocannabinol (THC), which may vary according to genetic factors and environmental influences. On the basis of the THC content all cannabis plants are divided into fibre-type and drug-type plants. The fibre-type plant does not exceed 0.4 per cent of THC while the drug-type plant usually contains up to 5 per cent of THC, though higher percentages (up to 10 per cent) have been reported. A study of the characteristics of cannabis seeds and the influence of environmental conditions on the content of THC in cannabis plants grown in northern, southern and insular Italy has shown that the fibre-type plants contain mean values of THC in a range from 0.058 to 0.299 per cent. The content of THC in the drug-type plants grown in Sicily and Tuscany ranged from 0.82 to 1.31 per cent +/- 0.49 per cent. In 1984, the Commission of the European Communities prepared a regulation to prevent diffusion of the drug-type cannabis, providing that raw material could not be imported if its THC content exceeded 0.5 per cent from 1984 to 1987 and after that period the maximum limit would be set up to 0.3 per cent.

Cannabis↗
PubMed2002

[Molecular biological studies on diversity of secondary metabolism in medicinal plants and application to the production in transgenic plants].

A molecular biological approach was applied to the study of diversity and regulation of secondary metabolism in medicinal plants at various levels. For the inter-species diversity, RFLP (restriction fragment length polymorphism) and RAPD (random amplified polymorphic DNA) analyses of genomic DNA were performed on the plants, belonging to the same genus or family and containing related compounds. Phylogenetic trees of lupin alkaloid containing plants and other medicinal plants, based on RFLP and/or RAPD profiles, showed the relationship between the diversities in genomes and secondary metabolisms. The chemotypes regarding anthocyanin production in Perilla frutescens var. crispa, were subjected to the study on intra-species diversity. The structural genes and the regulatory genes involved in anthocyanin biosynthesis were isolated and their expression in red and green forms was determined by Northern blot analysis. The expression of all structural genes examined was co-ordinately regulated in form-specific manner and by light illumination. The anthocyanin production was enhanced in transgenic plants over-expressing Myc homologue genes from perilla. These results suggested that a protein complex including bHLH factors might regulate the expression of a series of structural genes. Additionally, cDNAs coding anthocyanin 5-O-glucosyltransferase and anthocyanidin synthase were isolated and characterized using recombinant proteins for the time. In conclusion, it was indicated that the molecular biological techniques are powerful tools for the investigation of diversity and regulation of and for the genetic engineering of secondary metabolism in medicinal plants.

Anthocyanins↗
PubMed1988

Concentrations of Co, Cd, Cr, Ni, and Zn in crop plants cultivated in the vicinity of coal-fired power plants.

In order to determine the effect of airborne emissions of trace elements (Co, Cd, Cr, Ni and Zn) from coal-fired power plants on the environment, concentrations were determined in different species of agricultural plants from the local environment (1-15 km radius) and compared with the corresponding concentrations in soils and fallout. The spatial distribution of trace elements in the soil over 7 years did not indicate any significant increased exposure to plants. In agricultural soils exposed to particle fallout produced by the combustion of brown coal, the trace element content changes slowly; it may decrease owing to its removal with the harvesting of crop plants and due to an insufficient supply of fertilizers. Particle fallout from local power plants is too small to change significantly the natural distribution pattern of trace elements in soils and in plant tissues. For monitoring purposes attention should be paid to the leaves and roots of sugar beet and oat seeds in the vicinity of coal-fired power plants.

Cadmium↗
PubMed2005

Screening plant species native to Taiwan for remediation of 137Cs-contaminated soil and the effects of K addition and soil amendment on the transfer of 137Cs from soil to plants.

This study aims to screen plant species native to Taiwan that could be used to eliminate (137)Cs radionuclides from contaminated soil. Four kinds of vegetables and two kinds of plants known as green manures were used for the screening. The test plants were cultivated in (137)Cs-contaminated soil and amended soil which is a mixture of the contaminated one with a horticultural soil. The plant with the highest (137)Cs transfer factor was used for further examination on the effects of K addition on the transfer of (137)Cs from the soils to the plant. Experimental results revealed that plants cultivated in the amended soil produced more biomass than those in the contaminated soil. Rape exhibited the highest production of aboveground parts, and had the highest (137)Cs transfer factor among all the tested plants. The transfer of (137)Cs to the rape grown in the soil to which 100 ppm KCl commonly used in local fertilizers had been added, were restrained. Results of this study indicated that rape, a popular green manure in Taiwan, could remedy (137)Cs-contaminated soil.

Biodegradation, Environmental↗
PubMed2006

Ghrelin in plants: what is the function of an appetite hormone in plants?

In the present work, we provide compelling evidence for the expression of a ghrelin-like peptide hormone that has only been associated with animals, in various plant tissues. Ghrelin, the appetite stimulating hormone, has been identified from a number of different species including humans, rat, pig, mouse, gerbil, eel, goldfish, bullfrog and chicken. The study here was conducted using an immunohistochemistry assay to screen whether plants have any ghrelin immunoreactivity. In this respect, Prunus x domestica L. and Marus alba were examined. Immunohistochemistry results showed that there is a strong human ghrelin immunoreactivity substance in the parenchyma cells of these plants. This was entirely unexpected since this hormone was considered to be present solely in animals. Thus, this study is the first to report the presence of a peptide with ghrelin-like activity in plants, a finding that has only been observed in the animal kingdom. RIA analysis confirmed that these plants contain significant amounts of this substance. Furthermore, reverse-phase HPLC analyses of plant extracts showed an elution characteristic of the peptide identical to that of human ghrelin. In general, fruit from both plants had higher levels of the peptide than the vegetative parts.

Chromatography, High Pressure Liquid↗
PubMed2003

Soil availability, plant uptake and soil to plant transfer of 99Tc--a review.

The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the potential for phytoextraction of radionuclides from contaminated effluent and soil. Vascular plants have a high 99Tc uptake capacity, a strong tendency to transport it to shoot material and accumulate it in vegetative rather than reproductive structures. The mechanisms that control 99Tc entry to plants have not been identified and there has been little discussion of the potential for phytoextraction of 99Tc contaminated effluents or soil. Here we review soil availability, plant uptake mechanisms and soil to plant transfer of 99Tc in the light of recent advances in soil science, plant molecular biology and phytoextraction technologies. We conclude that 99Tc might not be highly available in the long term from up to 50% of soils worldwide, and that no single mechanism that might be easily targeted by recombinant DNA technologies controls 99Tc uptake by plants. Overall, we suggest that Tc might be less available in terrestrial ecosystems than is often assumed but that nevertheless the potential of phytoextraction as a decontamination strategy is probably greater for 99Tc than for any other nuclide of radioecological interest.

Biological Availability↗
PubMed1996

Phosphorylation of phosphoenolpyruvate carboxykinase in plants. Studies in plants with C4 photosynthesis and Crassulacean acid metabolism and in germinating seeds.

We have previously shown that phosphoenolpyruvate carboxykinase (PEPCK) is phosphorylated in vivo in the cotyledons of darkened cucumber seedlings and that phosphorylation is reversed by light [Walker and Leegood (1995) FEBS Lett. 362, 70-74]. In this study the molecular mass of PEPCK was estimated in a range of gluconeogenic seedlings and in leaves of C4 plants and plants with Crassulacean acid metabolism (CAM). Phosphorylation of PEPCK was studied in these plants by feeding tissues with [32P]Pi and assessing phosphorylation by SDS/PAGE and autoradiography of either total proteins or of immunoprecipitated protein. In gluconeogenic seedlings and most CAM plants PEPCK had a molecular mass of 74 kDa, whereas in C4 grasses the molecular mass of PEPCK was always smaller and varied from 67-71 kDa. In all gluconeogenic seedlings and leaves of CAM plants PEPCK was phosphorylated, but it was not phosphorylated in all species of C4 grasses studied. In CAM plants, phosphorylation of PEPCK occurred at night and dephosphorylation occurred during the day. In C4 grasses phosphorylation occurred when leaves were darkened and the enzyme was dephosphorylated following illumination, but it was only phosphorylated in those plants with larger (71 kDa) molecular mass forms of PEPCK.

Carboxylic Acids↗
PubMed1996

Reduction of the cytosolic fructose-1,6-bisphosphatase in transgenic potato plants limits photosynthetic sucrose biosynthesis with no impact on plant growth and tuber yield.

Sucrose produced in source leaves is the predominant carbon source for developing sink tissues in most higher plants. Consequently the rate of sucrose synthesis is likely to be important for sink development and final crop yield. Two sucrose biosynthetic enzymes are believed to possess regulatory properties with respect to the rate of sucrose synthesis: (i) cytosolic FBPase and (ii) sucrose phosphate synthase. To study the impact of reduced photosynthetic sucrose biosynthesis on plant growth and crop yield a cDNA clone encoding cytosolic FBPase was isolated from a potato leaf cDNA library and used for antisense experiments in transgenic potato plants. The cDNA clone cy-F1, containing an open reading frame of 1020 bp highly homologous (85%) to other known sequences of plant cytosolic FBPases, was cloned in reversed orientation between the 35S CaMV promoter and the octopine synthase polyadenylation signal. Out of 75 independent transformants five transgenic lines having 9 to 55% of the wild-type FBPase activity were chosen for further analysis. A 45% reduction of the cytosolic FBPase activity did not cause any measurable change in metabolite concentrations, growth behaviour or photosynthetic parameters of the transgenic plants. Inhibition of cytosolic FBPase activity below 20% of the wild-type activity led to an accumulation of 3-PGA, triose-phosphates and fructose-1,6-biphosphate in source leaves. This resulted in a reduced light-saturated rate of assimilation measured via gas exchange and a decreased photosynthetic rate under conditions of the leaf disc electrode with saturating light and CO2. Measuring photosynthetic carbon fluxes by labelling leaf discs with 14CO2 revealed a 53-65% reduction of sucrose synthesis whereas starch synthesis decreased only by 18-24%. The flux into the anionic and cationic fraction was not altered. Despite these changes steady-state sucrose concentrations were not effected in source leaves from transgenic plants. Starch accumulated by more than a factor of 3 compared with wild-type leaves and was degraded during the night. This provides strong evidence for the hypothesis that hexoses and/or hexosephosphates are exported out of the chloroplasts, thereby circumventing the limitation of sucrose biosynthesis caused by the inhibition of cytosolic FBPase in the dark. Accordingly, plant growth and potato tuber yield remained unaltered. From these data it can be concluded that a reduced photosynthetic sucrose biosynthetic capacity can be efficiently compensated without any reduction in crop yield under greenhouse or growth chamber conditions by changing carbon export strategy. Whether the same holds true for field conditions remains to be elucidated.

Agrobacterium tumefaciens↗
PubMed2004

Hydraulic architecture of plants of Helianthus annuus L. cv. Margot: evidence for plant segmentation in herbs.

The hydraulic architecture of sunflower (Helianthus annuus L. cv. Margot) was studied in terms of the partitioning of the hydraulic conductance (Kleaf) of leaves inserted at progressively more apical nodes both in growing plants (GP) and in plants at full anthesis (mature plants, MP). Leaf conductance to water vapour (gL), leaf water potential (PsiL), leaf water potential at zero turgor (Psi tlp), and leaf osmotic potential at full turgor (pi0) were also measured. Sunflower plants showed gL and Kleaf values significantly increasing in the acropetal direction, while PsiL of basal leaves was significantly more negative than that of distal leaves; Psi tlp markedly decreased in the acropetal direction in MP so that leaves of MP retained increasingly more turgor the more apical they were. This hydraulic pattern, already present in very young plants (GP), strongly favours apical leaves. These data suggest that the progressive leaf dieback starting from the stem base, as observed when the inflorescence of sunflower reached maturity, might be due to time-dependent loss of hydraulic conductance. In fact, Kleaf loss was correlated with PsiL drop and stomatal closure. Leaf dehydration was aggravated by solute exportation from the basal towards the apical leaves, as revealed by the acropetal decrease of pi0. Kleaf was shown to be linearly and positively related to the prevailing ambient irradiance during plant growth, thus suggesting that leaf hydraulics is very sensitive to environmental conditions. It was concluded that the pronounced apical dominance of some sunflower cultivars is determined, among other factors, by plant hydraulic architecture.

Helianthus↗
PubMed2006

SHR5: a novel plant receptor kinase involved in plant-N2-fixing endophytic bacteria association.

Endophytic nitrogen-fixing bacteria have been isolated from graminaceous plants such as maize, rice, and sugarcane. They are thought to promote plant growth, not only by fixing nitrogen, but also by the production of plant hormones. The molecular mechanisms involved in this interaction are not yet clear. In this work, the identification of a receptor-like kinase (RLK), named SHR5, which may participate in signal transduction involved in the establishment of plant-endophytic bacteria interaction is described for the first time. SHR5 seems to be part of a novel subclass of RLKs present in a wide range of plant species. The expression of this gene is down-regulated in sugarcane plants associated exclusively with beneficial endophytic bacteria and is not a general response caused by micro-organisms or abiotic stress. In addition, more successful sugarcane-endophytic bacteria associations have a more pronounced decrease in SHR5 expression, suggesting that SHR5 mRNA levels in plant cells are inversely related to the efficiency of the association.

Actinobacteria↗
PubMed2000

Plant growth-promoting bacteria that decrease heavy metal toxicity in plants.

Kluyvera ascorbata SUD165 and a siderophore-overproducing mutant of this bacterium, K. ascorbata SUD165/26, were used to inoculate tomato, canola, and Indian mustard seeds which were then grown in soil for 25-42 days in the presence of either nickel, lead, or zinc. The parameters that were monitored included plant wet and dry weight, protein and chlorophyll content in the plant leaves, and concentration of heavy metal in the plant roots and shoots. As indicated by a decrease in the measured values of these parameters, in all instances, plant growth was inhibited by the presence of the added metal. Both bacterial strains were effective, although not always to a statistically significant extent, at relieving a portion of the growth inhibition caused by the metals. In most cases, the siderophore overproducing mutant K. ascorbata 165/26 exerted a more pronounced effect on plant growth than did the wild-type bacterium K. ascorbata SUD165. The data suggest that the ability of these bacteria to protect plants against the inhibitory effects of high concentrations of nickel, lead, and zinc is related to the bacteria providing the plants with sufficient iron.

Biodegradation, Environmental↗
PubMed2003

Field survey of Glycyrrhiza plants in central Asia (2). Characterization of phenolics and their variation in the leaves of Glycyrrhiza plants collected in Kazakhstan.

A new prenylated flavanone, licoleafol, and a new prenylated dihydrostilbene, uralstilbene, together with four known compounds, 8-dimethylallyleriodictyol, sophoraflavanone B, gancaonin R, and 6-dimethylallyleriodictyol, were isolated from the leaves of Glycyrrhiza uralensis collected in Kazakhstan. HPLC analysis of the leaves of Glycyrrhiza plants collected in Kazakhstan showed that both G. uralensis-specific and Glycyrrhiza glabra-specific compounds were detected in the leaves of the morphologically intermediate-type plants, suggesting that the intermediate-type plant is a hybrid of G. glabra and G. uralensis. In addition, HPLC profiles of leaf extracts from offspring of intermediate-type plants were divided into the three types: the G. uralensis type, G. glabra type, and the intermediate type. From these results, it appears likely that the intermediate-type plant back-crosses with G. glabra and G. uralensis to generate a G. glabra-type plant and a G. uralensis-type plant, respectively.

Glycyrrhiza↗
PubMed1999

[Studies on the plant hormones produced by 5 species of endophytic fungi isolated from medicinal plants (Orchidacea)].

OBJECTIVE: To study the plant hormones produced by 5 species of endophytic fungi isolated from medicinal plants and to illustrate the mechanism on endophytic fungi stimulating the growth of plants. METHODS: Extracting plant hormones from mycelia and its culture solution with organic solvent, and detecting them by HPLC. RESULTS: One or more plant hormones [GA3 (Gibberellin), IAA (Indoleacetic acid), ABA (Abscisic acid), Z (Zeatin), ZR (Zeatin riboside)] were detected from the mycelia and its culture solution. CONCLUSIONS: The plant hormones produced by the endophytic fungi are important materials that may be used to reveal the mechanism of endophytic fungi stimulating the growth of medicinal plants (Orchidacea).

Abscisic Acid↗
PubMed1992

Plant nurseries: a reliable resource for plant identification?

Poison Centers frequently rely on the assistance of local plant nurseries to identify unknown plants involved in exposures. The reliability and accuracy of utilizing this method has never been studied; therefore, our objective was to evaluate this primary resource of plant identification. A study was done in which callers were instructed to take plant samples to a local nursery for visual identification. Once the patient was treated according to our normal protocol, the plant specimen was sent to a botanist for a second identification. The botanist provided his identification results through a blinded process. The collected data was gathered from 68 cases that completed the necessary study criteria. In 58% of the cases, plant nurseries were an unreliable source for plant identification. These incorrect identifications resulted in the "undertreatment" in 24% of the exposures.

Animals↗
PubMed2006

Effects of potato plants expressing a barley cystatin on the predatory bug Podisus maculiventris via herbivorous prey feeding on the plant.

The aim of this study was to assess the effects of potato plants expressing a barley cystatin on a potentially cystatin-susceptible natural enemy by predation on susceptible and non-susceptible preys feeding on the plant. We have focussed on the impact of the variant HvCPI-1 C68 --> G, in which the only cysteine residue was changed by a glycine, on the growth and digestive physiology of the Colorado potato beetle (CPB), Leptinotarsa decemlineata, and the Egyptian cotton leafworm (ECW), Spodoptera littoralis. Moreover, we have studied the prey-mediated effects of the barley cystatin at the third trophic level, using the predatory spined soldier bug (SSB), Podisus maculiventris, as a model. Feeding trials conducted with CPB larvae reared on transgenic potato plants expressing the C68 --> G variant resulted in significantly lower weight gains compared to those fed on non-transformed (NT) plants. On the contrary, larger weight gains were obtained when ECW larvae, that lack digestive cysteine proteases, were reared on transgenic potato expressing the cystatin, as compared to larvae fed on NT plants. No negative effects on survival and growth were observed when SSB nymphs were exposed to HvCPI-1 C68 --> G by predation on either CPB or ECW larvae reared on transgenic potato plants expressing the barley cystatin, despite the fact that the inhibitor suppressed in vitro gut proteolysis of the predatory bug. To investigate the physiological background, biochemical analysis were carried out on guts of insects dissected at the end of the feeding assays.

Amino Acid Substitution↗
PubMed2006

Microbial endoxylanases: effective weapons to breach the plant cell-wall barrier or, rather, triggers of plant defense systems?

Endo-beta-1,4-xylanases (EC 3.2.1.8) are key enzymes in the degradation of xylan, the predominant hemicellulose in the cell walls of plants and the second most abundant polysaccharide on earth. A number of endoxylanases are produced by microbial phytopathogens responsible for severe crop losses. These enzymes are considered to play an important role in phytopathogenesis, as they provide essential means to the attacking organism to break through the plant cell wall. Plants have evolved numerous defense mechanisms to protect themselves against invading pathogens, amongst which are proteinaceous inhibitors of cell wall-degrading enzymes. These defense mechanisms are triggered when a pathogen-derived elicitor is recognized by the plant. In this review, the diverse aspects of endoxylanases in promoting virulence and in eliciting plant defense systems are highlighted. Furthermore, the role of the relatively recently discovered cereal endoxylanase inhibitor families TAXI (Triticum aestivum xylanase inhibitor) and XIP (xylanase inhibitor protein) in plant defense is discussed.

Bacteria↗
PubMed2006

Volatile signaling in plant-plant interactions: "talking trees" in the genomics era.

Plants may "eavesdrop" on volatile organic compounds (VOCs) released by herbivore-attacked neighbors to activate defenses before being attacked themselves. Transcriptome and signal cascade analyses of VOC-exposed plants suggest that plants eavesdrop to prime direct and indirect defenses and to hone competitive abilities. Advances in research on VOC biosynthesis and perception have facilitated the production of plants that are genetically "deaf" to particular VOCs or "mute" in elements of their volatile vocabulary. Such plants, together with advances in VOC analytical instrumentation, will allow researchers to determine whether fluency enhances the fitness of plants in natural communities.

Adaptation, Physiological↗