| ectomycorrhizal communities associated with populus tremula growing on a heavy metal contaminated site. | european aspen is one of the most widely distributed trees in central europe and is a typical early colonizer of poor and disturbed soils. however, little is known about ectomycorrhizal (ecm) fungi in these ecosystems. we examined the ecm community of european aspen growing on a heavily contaminated site in southern austria by analysing ecm roots, sorting them into morphotypes, subjecting them to dna extraction, pcr, and dna sequencing. ecm root symbionts were sampled two times in 2004. during t ... | 2008 | 18692376 |
| antifeedants and feeding stimulants in bark extracts of ten woody non-host species of the pine weevil, hylobius abietis. | bark of ten woody species, known to be rejected as a food source by the pine weevil, hylobius abietis, were sequentially extracted by a soxhlet apparatus with pentane followed by methanol. species were alder (alnus glutinosa), aspen (populus tremula), beech (fagus sylvatica), guelder rose (viburnum opulus), holly (ilex aquifolium), horse chestnut (aesculus hippocastanum), lilac (syringa vulgaris), spindle tree (evonymus europaeus), walnut (juglans regia), and yew (taxus baccata). bark of each sp ... | 2008 | 18719963 |
| evaluating ascorbate oxidase as a plant defense against leaf-chewing insects using transgenic poplar. | ascorbate is the major water-soluble antioxidant in plants and animals, and it is an essential nutrient for most insect herbivores. therefore, ascorbate oxidase (ao) has been proposed to function as a plant defense that decreases the availability of ascorbate to insects. this hypothesis was tested by producing transgenic poplar (populus tremula x populus alba; salicaceae) with 14- to 37-fold higher foliar ao activities than control (wild type) leaves and feeding these leaves to lymantria dispar ... | 2008 | 18773241 |
| ozone-induced changes in photosynthesis and photorespiration of hybrid poplar in relation to the developmental stage of the leaves. | young poplar trees (populus tremula michx. x populus alba l. clone inra 717-1b4) were subjected to 120 ppb of ozone for 35 days in phytotronic chambers. treated trees displayed precocious leaf senescence and visible symptoms of injury (dark brown/black upper surface stippling) exclusively observed on fully expanded leaves. in these leaves, ozone reduced parameters related to photochemistry (chl content and maximum rate of photosynthetic electron transport) and photosynthetic co(2) fixation [net ... | 2008 | 18823329 |
| bioremediation of 2,4,6-trinitrotoluene by bacterial nitroreductase expressing transgenic aspen. | trees belonging to the genus populus are often used for phytoremediation due to their deep root formation, fast growth and high transpiration rates. here, we study the capacity of transgenic hybrid aspen (populus tremula x tremuloides var. etropole) which expresses the bacterial nitroreductase gene, pnra, to tolerate and take-up greater amounts of the toxic and recalcitrant explosive, 2,4,6-trinitrotoluene (tnt) from contaminated waters and soil. transgenic aspen tolerate up to 57 mg tnt/l in hy ... | 2008 | 18939578 |
| analysis of nasturtium tmnxg1 complexes by crystallography and molecular dynamics provides detailed insight into substrate recognition by family gh16 xyloglucan endo-transglycosylases and endo-hydrolases. | reorganization and degradation of the wall crosslinking and seed storage polysaccharide xyloglucan by glycoside hydrolase family 16 (gh16) endo-transglycosylases and hydrolases are crucial to the growth of the majority of land plants, affecting processes as diverse as germination, morphogenesis, and fruit ripening. a high-resolution, three-dimensional structure of a nasturtium (tropaeolum majus) endo-xyloglucanase loop mutant, tmnxg1-deltayniig, with an oligosaccharide product bound in the negat ... | 2009 | 19004021 |
| postillumination isoprene emission: in vivo measurements of dimethylallyldiphosphate pool size and isoprene synthase kinetics in aspen leaves. | the control of foliar isoprene emission is shared between the activity of isoprene synthase, the terminal enzyme catalyzing isoprene formation from dimethylallyldiphosphate (dmadp), and the pool size of dmadp. due to limited in vivo information of isoprene synthase kinetic characteristics and dmadp pool sizes, the relative importance of these controls is under debate. in this study, the phenomenon of postillumination isoprene release was employed to develop an in vivo method for estimation of th ... | 2009 | 19129417 |
| steam explosion lignins; their extraction, structure and potential as feedstock for biodiesel and chemicals. | in the present study, a steam explosion wood pre-treatment process, optimized earlier with respect to ethanol production, has been applied to both softwoods (picea abies and pinus sylvestris) and hardwoods (betula verrucosa and populus tremula). the alkaline extractable lignins have then been isolated to investigate lignin separation efficiency and lignin structure and to evaluate their potential for producing value-added products, such as biodiesel components or chemicals, in terms of the purit ... | 2009 | 19157871 |
| a unique program for cell death in xylem fibers of populus stem. | maturation of the xylem elements involves extensive deposition of secondary cell-wall material and autolytic processes resulting in cell death. we describe here a unique type of cell-death program in xylem fibers of hybrid aspen (populus tremula x p. tremuloides) stems, including gradual degradative processes in both the nucleus and cytoplasm concurrently with the phase of active cell-wall deposition. nuclear dna integrity, as determined by tunel (terminal deoxynucleotidyl transferase-mediated d ... | 2009 | 19175765 |
| the control of autumn senescence in european aspen. | the initiation, progression, and natural variation of autumn senescence in european aspen (populus tremula) was investigated by monitoring chlorophyll degradation in (1) trees growing in natural stands and (2) cloned trees growing in a greenhouse under various light regimes. the main trigger for the initiation of autumn senescence in aspen is the shortening photoperiod, but there was a large degree of variation in the onset of senescence, both within local populations and among trees originating ... | 2009 | 19201914 |
| differences in leaf characteristics between ozone-sensitive and ozone-tolerant hybrid aspen (populus tremula x populus tremuloides) clones. | the authors analyzed a suite of leaf characteristics that might help to explain the difference between ozone-sensitive and ozone-tolerant hybrid aspen (populus tremula l. x populus tremuloides michx.) clones. an open-field experiment comprising ambient ozone and 1.5x ambient ozone concentration (about 35 ppb) and two soil nitrogen regimes (60 and 140 kg n ha(-1) year(-1)) was conducted over two growing seasons on potted plants of eight hybrid aspen clones. four of the clones had previously been ... | 2009 | 19203932 |
| plasma membrane microdomains from hybrid aspen cells are involved in cell wall polysaccharide biosynthesis. | detergent-resistant plasma membrane microdomains [drms (detergent-resistant membranes)] were isolated recently from several plant species. as for animal cells, a large range of cellular functions, such as signal transduction, endocytosis and protein trafficking, have been attributed to plant lipid rafts and drms. the data available are essentially based on proteomics and more approaches need to be undertaken to elucidate the precise function of individual populations of drms in plants. we report ... | 2009 | 19216717 |
| nucleotide diversity among natural populations of a north american poplar (populus balsamifera, salicaceae). | poplars (populus spp.) comprise an important component of circumpolar boreal forest ecosystems and are the model species for tree genomics. in this study, we surveyed genetic variation and population differentiation in three nuclear genes among populations of balsam poplar (populus balsamifera) in north america. we examined nucleotide sequence variation in alcohol dehydrogenase 1 (adh1) and glyceraldehyde 3-phosphate dehydrogenase (g3pdh), two well-studied nuclear loci in plants, and abscisic ac ... | 2009 | 19228296 |
| the effects on lignin structure of overexpression of ferulate 5-hydroxylase in hybrid poplar. | poplar (populus tremula x alba) lignins with exceedingly high syringyl monomer levels are produced by overexpression of the ferulate 5-hydroxylase (f5h) gene driven by a cinnamate 4-hydroxylase (c4h) promoter. compositional data derived from both standard degradative methods and nmr analyses of the entire lignin component (as well as isolated lignin fraction) indicated that the c4hf5h transgenic's lignin was comprised of as much as 97.5% syringyl units (derived from sinapyl alcohol), the remaind ... | 2009 | 19386808 |
| the cytokinin type-b response regulator ptrr13 is a negative regulator of adventitious root development in populus. | adventitious root formation at the base of plant cuttings is an innate de novo organogenesis process that allows massive vegetative propagation of many economically and ecologically important species. the early molecular events following shoot excision are not well understood. using whole-genome microarrays, we detected significant transcriptome remodeling during 48 h following shoot removal in populus tremula x populus alba softwood cuttings in the absence of exogenous auxin, with 27% and 36% o ... | 2009 | 19395410 |
| korrigan1 and its aspen homolog pttcel9a1 decrease cellulose crystallinity in arabidopsis stems. | korrigan1 (kor1) is a membrane-bound cellulase implicated in cellulose biosynthesis. pttcel9a1 from hybrid aspen (populus tremula l. x tremuloides michx.) has high sequence similarity to kor1 and we demonstrate here that it complements kor1-1 mutants, indicating that it is a kor1 ortholog. we investigated the function of pttcel9a1/kor1 in arabidopsis secondary growth using transgenic lines expressing 35s::pttcel9a1 and the kor1 mutant line irx2-2. the presence of elevated levels of pttcel9a1/kor ... | 2009 | 19398462 |
| the ectomycorrhizal morphotype pinirhiza sclerotia is formed by acephala macrosclerotiorum sp. nov., a close relative of phialocephala fortinii. | relatively few ectomycorrhizal fungal species are known to form sclerotia. usually, sclerotia are initiated at the extraradical mycelium. in this study, we present anatomical and ultrastructural evidence for the formation of sclerotia directly in the hyphal mantle of the mycorrhizal morphotype pinirhiza sclerotia. a dark-pigmented fungal strain was isolated from pinirhiza sclerotia and identified by molecular tools as acephala macrosclerotiorum sp. nov., a close relative of phialocephala fortini ... | 2009 | 19415343 |
| performance and secondary chemistry of two hybrid aspen (populus tremula l. x populus tremuloides michx.) clones in long-term elevated ozone exposure. | the effects of moderately elevated ozone (ca. 35 ppb) on the growth and secondary chemistry of the leaves of two soil-grown finnish hybrid aspen (populus tremula l. x populus tremuloides michx.) clones with different ozone sensitivities were studied at an open-air exposure field in kuopio, finland. stomatal conductance, photosynthetic rate, and chlorophyll fluorescence were measured during the third growing season. foliar phenolic concentrations, ergosterol concentration of fine roots, and final ... | 2009 | 19462207 |
| stable expression of the chlorocatechol dioxygenase gene from ralstonia eutropha nh9 in hybrid poplar cells. | the cbna gene encoding chlorocatechol dioxygenase from the soil bacterium ralstonia eutropha nh9 under the control of a modified cauliflower mosaic virus 35s promoter was introduced into a hybrid poplar (populus tremula x p. tremuloides). integration of the cbna gene in transgenic poplar was confirmed by pcr and genomic southern blot analysis. expression of the cbna gene was analyzed by western blot analysis. transgenic poplar calli efficiently converted 3-chlorocatechol to 2-chloro-cis,cis-muco ... | 2009 | 19502754 |
| chloroplast parameters differ in wild type and transgenic poplars overexpressing gsh1 in the cytosol. | poplar mutants overexpressing the bacterial genes gsh1 or gsh2 encoding the enzymes of glutathione biosynthesis are among the best-characterised transgenic plants. however, this characterisation originates exclusively from laboratory studies, and the performance of these mutants under field conditions is largely unknown. here, we report a field experiment in which the wild-type poplar hybrid populus tremula x p. alba and a transgenic line overexpressing the bacterial gene gsh1 encoding gamma-glu ... | 2009 | 19538400 |
| selective histories of poplar protease inhibitors: elevated polymorphism, purifying selection, and positive selection driving divergence of recent duplicates. | to further our understanding of plant defense evolution and the consistency of selection at the nucleotide level we analysed polymorphism data from five protease inhibitor (pi) genes in populus balsamifera. we compared diversity at the five pi genes to diversity at nondefense loci in both range-wide samples as well as in two subpopulations, one from the northern edge of the species range and one from the southern edge of the range. we also compared our data with previously reported diversity in ... | 2009 | 19566812 |
| uv-b-responsive micrornas in populus tremula. | micrornas (mirnas) play vital roles in down-regulating gene expression at the post-transcriptional level. a set of 24 uv-b stress-responsive mirnas (13 up-regulated and 11 down-regulated) was identified in populus tremula plantlet by expression profiling with our in-house mirna filter array. six of the uv-b-responsive mirna and their corresponding target genes were verified for their expressions by rna blotting and quantitative reverse transcription pcr (qrt-pcr), respectively. the predicted tar ... | 2009 | 19628301 |
| natural selection on synonymous and nonsynonymous mutations shapes patterns of polymorphism in populus tremula. | one important goal of population genetics is to understand the relative importance of different evolutionary processes for shaping variation in natural populations. here, i use multilocus data to show that natural selection on both synonymous and nonsynonymous mutations plays an important role in shaping levels of synonymous polymorphism in european aspen (populus tremula). previous studies have documented a preferential fixation of synonymous mutations encoding preferred codons in p. tremula. t ... | 2010 | 19837657 |
| the ectomycorrhizal fungus laccaria bicolor stimulates lateral root formation in poplar and arabidopsis through auxin transport and signaling. | the early phase of the interaction between tree roots and ectomycorrhizal fungi, prior to symbiosis establishment, is accompanied by a stimulation of lateral root (lr) development. we aimed to identify gene networks that regulate lr development during the early signal exchanges between poplar (populus tremula x populus alba) and the ectomycorrhizal fungus laccaria bicolor with a focus on auxin transport and signaling pathways. our data demonstrated that increased lr development in poplar and ara ... | 2009 | 19854859 |
| genome scale transcriptome analysis of shoot organogenesis in populus. | our aim is to improve knowledge of gene regulatory circuits important to dedifferentiation, redifferentiation, and adventitious meristem organization during in vitro regeneration of plants. regeneration of transgenic cells remains a major obstacle to research and commercial deployment of most taxa of transgenic plants, and woody species are particularly recalcitrant. the model woody species populus, due to its genome sequence and amenability to in vitro manipulation, is an excellent species for ... | 2009 | 19919717 |
| structure and vascular tissue expression of duplicated terminal ear1-like paralogues in poplar. | terminal ear1-like (tel) genes encode putative rna-binding proteins only found in land plants. previous studies suggested that they may regulate tissue and organ initiation in poaceae. two tel genes were identified in both populus trichocarpa and the hybrid aspen populus tremula x p. alba, named, respectively, poptrtel1-2 and ptatel1-2. the analysis of the organisation around the poptrtel genes in the p. trichocarpa genome and the estimation of the synonymous substitution rate for ptatel1-2 gene ... | 2010 | 19943172 |
| isolation and characterization of osmotic stress-induced genes in poplar cells by suppression subtractive hybridization and cdna microarray analysis. | osmotic stress induces changes in the expression of various genes including those associated with drought tolerance, cell wall metabolism and defense. we isolated 852 cdna clones, the expression of which is induced by osmotic stress, from cells of a hybrid poplar (populus alba x populus tremula var. glandulosa) by suppression subtractive hybridization after mannitol treatment. we examined how stress affected their expression using cdna microarray analysis, which identified 104 genes significantl ... | 2010 | 19962907 |
| characterization of a saccharide-binding protein from talisia esculenta seeds with trypsin inhibitory activity. | some proteins exhibit characteristics that suggest they have a primary, if not an exclusive role in nutrient reserve storage. the best studied examples are the storage proteins that accumulate specifically in developing seeds. some of these protein demonstrate biological activities that could contribute to resistance to pest, pathogens or abiotic stresses. in this study we present the biochemical characterization and cloning of the major protein from seeds of t. esculenta (talisin), a member of ... | 2009 | 20001918 |
| real-time monitoring of herbivore induced volatile emissions in the field. | when plants are damaged by herbivorous insects they emit a blend of volatile organic compounds (vocs) which include a range or terpenoids and green leaf volatiles (glvs) formed via different metabolic pathways. the precise timing of these emissions upon the onset of herbivore feeding has not been fully elucidated, and the information that is available has been mainly obtained through laboratory based studies. we investigated emissions of vocs from populus tremula l. xp. tremuloides michx. during ... | 2010 | 20002328 |
| redox states of glutathione and ascorbate in root tips of poplar (populus tremula x p. alba) depend on phloem transport from the shoot to the roots. | glutathione (gsh) and ascorbate (asc) are important antioxidants that are involved in stress defence and cell proliferation of meristematic root cells. in principle, synthesis of asc and gsh in the roots as well as asc and gsh transport from the shoot to the roots by phloem mass flow is possible. however, it is not yet known whether the asc and/or the gsh level in roots depends on the supply from the shoot. this was analysed by feeding mature leaves with [(14)c]asc or [(35)s]gsh and subsequent d ... | 2010 | 20022923 |
| seasonal and cell type specific expression of sulfate transporters in the phloem of populus reveals tree specific characteristics for so(4)(2-) storage and mobilization. | the storage and mobilization of nutrients in wood and bark tissues is a typical feature of trees. sulfur can be stored as sulfate, which is transported from source to sink tissues through the phloem. in the present study two transcripts encoding sulfate transporters (sultr) were identified in the phloem of grey poplar (populus tremula x p. alba). their cell-specific expression was analyzed throughout poplar in source tissues, such as mature leaves, and in sink tissues, such as the wood and bark ... | 2010 | 20087755 |
| nucleotide diversity and linkage disequilibrium in balsam poplar (populus balsamifera). | *current perceptions that poplars have high levels of nucleotide variation, large effective population sizes, and rapid decay of linkage disequilibrium are based primarily on studies from one poplar species, populus tremula. *we analysed 590 gene fragments (average length 565 bp) from each of 15 individuals from different populations from throughout the range of populus balsamifera. *nucleotide diversity (theta(total) = 0.0028, pi = 0.0027) was low compared with other trees and model agricultura ... | 2010 | 20122131 |
| acute metal stress in populus tremula x p. alba (717-1b4 genotype): leaf and cambial proteome changes induced by cadmium 2+. | the comprehension of metal homeostasis in plants requires the identification of molecular markers linked to stress tolerance. proteomic changes in leaves and cambial zone of populus tremula x p. alba (717-1b4 genotype) were analyzed after 61 days of exposure to cadmium (cd) 360 mg/kg soil dry weight in pot-soil cultures. the treatment led to an acute cd stress with a reduction of growth and photosynthesis. cd stress induced changes in the display of 120 spots for leaf tissue and 153 spots for th ... | 2010 | 20148406 |
| near-ambient ozone concentrations reduce the vigor of betula and populus species in finland. | in this review the main growth responses of finnish birch (betula pendula, b. pubescens) and aspen species (populus tremula and p. tremuloides x p. tremula) are correlated with ozone exposure, indicated as the aot40 value. data are derived from 23 different laboratory, open-top chamber, and free-air fumigation experiments. our results indicate that these tree species are sensitive to increasing ozone concentrations, though high intraspecific variation exists. the roots are the most vulnerable ta ... | 2009 | 20175439 |
| elevation of night-time temperature increases terpenoid emissions from betula pendula and populus tremula. | volatile organic compounds (vocs) are expected to have an important role in plant adaptation to high temperatures. the impacts of increasing night-time temperature on daytime terpenoid emissions and related gene expression in silver birch (betula pendula) and european aspen (populus tremula) clones were studied. the plants were grown under five different night-time temperatures (6, 10, 14, 18, and 22 degrees c) while daytime temperature was kept at a constant 22 degrees c. voc emissions were col ... | 2010 | 20181662 |
| over-expression of bacterial gamma-glutamylcysteine synthetase (gsh1) in plastids affects photosynthesis, growth and sulphur metabolism in poplar (populus tremula x populus alba) dependent on the resulting gamma-glutamylcysteine and glutathione levels. | we compared three transgenic poplar lines over-expressing the bacterial gamma-glutamylcysteine synthetase (gsh1) targeted to plastids. lines lggs6 and lggs12 have two copies, while line lggs20 has three copies of the transgene. the three lines differ in their expression levels of the transgene and in the accumulation of gamma-glutamylcysteine (gamma-ec) and glutathione (gsh) in leaves, roots and phloem exudates. the lowest transgene expression level was observed in line lggs6 which showed an inc ... | 2010 | 20199621 |
| poplar vulnerability to xylem cavitation acclimates to drier soil conditions. | xylem vulnerability to cavitation differs between tree species according to their drought resistance, more xerophilous species being more resistant to xylem cavitation. variability in xylem vulnerability to cavitation is also found within species, especially between in situ populations. the origin of this variability has not been clearly identified. here we analyzed the response of xylem hydraulic traits of populus tremula x populus alba trees to three different soil water regimes. stem xylem vu ... | 2010 | 20210873 |
| alteration of phya expression change circadian rhythms and timing of bud set in populus. | in many temperate woody species, dormancy is induced by short photoperiods. earlier studies have shown that the photoreceptor phytochrome a (phya) promotes growth. specifically, populus plants that over-express the oat phya gene (oatphyaox) show daylength-independent growth and do not become dormant. however, we show that oatphyaox plants could be induced to set bud and become cold hardy by exposure to a shorter, non-24 h diurnal cycle that significantly alters the relative position between endo ... | 2010 | 20229130 |
| changes in diurnal patterns within the populus transcriptome and metabolome in response to photoperiod variation. | changes in seasonal photoperiod provides an important environmental signal that affects the timing of winter dormancy in perennial, deciduous, temperate tree species, such as hybrid aspen (populus tremula x populus tremuloides). in this species, growth cessation, cold acclimation and dormancy are induced in the autumn by the detection of day-length shortening that occurs at a given critical day length. important components in the detection of such day-length changes are photoreceptors and the ci ... | 2010 | 20302601 |
| conserved ca-rich motifs in gene promoters of pt x tmyb021-responsive secondary cell wall carbohydrate-active enzymes in populus. | in order to understand gene regulation during wood formation, we cloned a myb46-like gene in hybrid aspen, populus tremula x tremuloides, called pt x tmyb021. phylogenetic and paired identity analysis of myb46-like genes in populus and arabidopsis reveals relationships between paralogous pairs of populus myb46-like proteins and their arabidopsis counterparts myb46 and myb83, and suggest that pt x tmyb021 is the ortholog of myb46. pt x tmyb021 is expressed mainly in xylem tissues, and transiently ... | 2010 | 20307500 |
| urbanization-related changes in european aspen (populus tremula l.): leaf traits and litter decomposition. | we investigated foliar and litter responses of european aspen (populus tremula l.) to urbanization, including factors such as increased temperature, moisture stress and nitrogen (n) deposition. leaf samples were collected in 2006-2008 from three urban and three rural forest stands in the helsinki metropolitan area, southern finland, and reciprocal litter transplantations were established between urban and rural sites. urban leaves exhibited a higher amount of epicuticular waxes and n concentrati ... | 2010 | 20338678 |
| admixture facilitates adaptation from standing variation in the european aspen (populus tremula l.), a widespread forest tree. | adaptation to new environments can start from new mutations or from standing variation already present in natural populations. whether admixture constrains or facilitates adaptation from standing variation is largely unknown, especially in ecological keystone or foundation species. we examined patterns of neutral and adaptive population divergence in populus tremula l., a widespread forest tree, using mapped molecular genetic markers. we detected the genetic signature of postglacial admixture be ... | 2010 | 20345678 |
| acclimation kinetics of physiological and molecular responses of plants to multiple mechanical loadings. | during their development, plants are subjected to repeated and fluctuating wind loads, an environmental factor predicted to increase in importance by scenarios of global climatic change. notwithstanding the importance of wind stress on plant growth and development, little is known about plant acclimation to the bending stresses imposed by repeated winds. the time-course of acclimation of young poplars (populus tremula l.xp. alba l.) to multiple stem bendings is studied here by following diameter ... | 2010 | 20363866 |
| targeted integration and removal of transgenes in hybrid aspen (populus tremula l. x p. tremuloides michx.) using site-specific recombination systems. | two site-specific recombination systems, cre/lox and flp/frt, were tested for marker gene removal and targeted gene transfer in a model tree system. a hybrid aspen clone (populus tremula x populus tremuloides) was co-transformed with plasmids containing either the flp or the cre recombinase, both under control of a heat-inducible promoter (hsp, gmhsp17.5-e from soybean) flanked by the two recognition sites (frt or lox). molecular investigations of heat-shock treated cre or flp transgenic lines i ... | 2010 | 20398239 |
| compartmentation of metals in foliage of populus tremula grown on soils with mixed contamination. ii. zinc binding inside leaf cell organelles. | the phytoextraction potential of plants for removing heavy metals from polluted soils is determined by their capacity to store contaminants in aboveground organs and complex them safely. in this study, the metal compartmentation, elemental composition of zinc deposits and zinc complexation within leaves from poplars grown on soil with mixed metal contamination was analysed combining several histochemical and microanalytical approaches. zinc was the only heavy metal detected and was stored in sev ... | 2011 | 20427108 |
| forage quantity, quality and depletion as scale-dependent mechanisms driving habitat selection of a large browsing herbivore. | 1. mechanisms that affect the spatial distribution of animals are typically scale-dependent and may involve forage distribution. forage quality and quantity are often inversely correlated and a much discussed trade-off is whether or not to select for high-quality forage at the expense of forage abundance. this discussion has rarely involved scale-dependence or been applied to northern browsing herbivores. at small spatial scales, browsers are assumed to select for the best quality forage. but, a ... | 2010 | 20443990 |
| flooding induced emissions of volatile signalling compounds in three tree species with differing waterlogging tolerance. | to gain insight into variations in waterlogging responsiveness, net assimilation rate, stomatal conductance, emissions of isoprene and marker compounds of anoxic metabolism ethanol and acetaldehyde, and stress marker compounds nitric oxide (no), volatile products of lipoxygenase (lox) pathway and methanol were studied in seedlings of temperate deciduous tree species alnus glutinosa, populus tremula and quercus rubra (from highest to lowest waterlogging tolerance) throughout sustained root zone w ... | 2010 | 20444211 |
| vascular-related nac-domain6 and vascular-related nac-domain7 effectively induce transdifferentiation into xylem vessel elements under control of an induction system. | we previously showed that the vascular-related nac-domain6 (vnd6) and vnd7 genes, which encode nam/ataf/cuc domain protein transcription factors, act as key regulators of xylem vessel differentiation. here, we report a glucocorticoid-mediated posttranslational induction system of vnd6 and vnd7. in this system, vnd6 or vnd7 is expressed as a fused protein with the activation domain of the herpes virus vp16 protein and hormone-binding domain of the animal glucocorticoid receptor, and the protein's ... | 2010 | 20488898 |
| changes in sulphur metabolism of grey poplar (populus x canescens) leaves during salt stress: a metabolic link to photorespiration. | the poplar hybrid populus x canescens (syn. populus tremula x populus alba) was subjected to salt stress by applying 75 mm nacl for 2 weeks in hydroponic cultures. decreasing maximum quantum yield (fv/fm) indicated damage of photosystem ii (ps ii), which was more pronounced under nitrate compared with ammonium nutrition. in vivo staining with diaminobenzidine showed no accumulation of h(2)o(2) in the leaf lamina; moreover, staining intensity even decreased. but at the leaf margins, development o ... | 2010 | 20516486 |
| circadian clock components regulate entry and affect exit of seasonal dormancy as well as winter hardiness in populus trees. | this study addresses the role of the circadian clock in the seasonal growth cycle of trees: growth cessation, bud set, freezing tolerance, and bud burst. populus tremula x populus tremuloides (ptt) late elongated hypocotyl1 (pttlhy1), pttlhy2, and timing of cab expression1 constitute regulatory clock components because down-regulation by rna interference of these genes leads to altered phase and period of clock-controlled gene expression as compared to the wild type. also, both rna interference ... | 2010 | 20530613 |
| mass spectrometry-based sequencing of lignin oligomers. | although the primary structure of proteins, nucleic acids, and carbohydrates can be readily determined, no sequencing method has been described yet for the second most abundant biopolymer on earth (i.e. lignin). within secondary-thickened plant cell walls, lignin forms an aromatic mesh arising from the combinatorial radical-radical coupling of monolignols and many other less abundant monomers. this polymerization process leads to a plethora of units and linkage types that affect the physicochemi ... | 2010 | 20554692 |
| gibberellin-associated cisgenes modify growth, stature and wood properties in populus. | we studied the effects on plant growth from insertion of five cisgenes that encode proteins involved in gibberellin metabolism or signalling. intact genomic copies of ptga20ox7, ptga2ox2,pt rgl1_1, ptrgl1_2 and ptgai1 genes from the genome-sequenced populus trichocarpa clone nisqually-1 were transformed into populus tremula × alba (clone inra 717-1b4), and growth, morphology and xylem cell size characterized in the greenhouse. each cisgene encompassed 1-2 kb of 5' and 1 kb of 3' flanking dna, as ... | 2011 | 20573046 |
| tyloses and phenolic deposits in xylem vessels impede water transport in low-lignin transgenic poplars: a study by cryo-fluorescence microscopy. | of 14 transgenic poplar genotypes (populus tremula × populus alba) with antisense 4-coumarate:coenzyme a ligase that were grown in the field for 2 years, five that had substantial lignin reductions also had greatly reduced xylem-specific conductivity compared with that of control trees and those transgenic events with small reductions in lignin. for the two events with the lowest xylem lignin contents (greater than 40% reduction), we used light microscopy methods and acid fuchsin dye ascent stud ... | 2010 | 20639405 |
| feeding on poplar leaves by caterpillars potentiates foliar peroxidase action in their guts and increases plant resistance. | peroxidases (pods) are believed to act as induced and constitutive defenses in plants against leaf-feeding insects. however, little work has examined the mode of action of pods against insects. putative mechanisms include the production of potentially antinutritive and/or toxic semiquinone free radicals and quinones (from the oxidation of phenolics), as well as increased leaf toughness. in this study, transgenic hybrid poplar saplings (populus tremula × populus alba) overexpressing horseradish p ... | 2010 | 20680646 |
| transcriptome responses to aluminum stress in roots of aspen (populus tremula). | ionic aluminum (mainly al3+) is rhizotoxic and can be present in acid soils at concentrations high enough to inhibit root growth. many forest tree species grow naturally in acid soils and often tolerate high concentrations of al. previously, we have shown that aspen (populus tremula) releases citrate and oxalate from roots in response to al exposure. to obtain further insights into the root responses of aspen to al, we investigated root gene expression at al conditions that inhibit root growth. | 2010 | 20727216 |
| antisense down-regulation of 4cl expression alters lignification, tree growth, and saccharification potential of field-grown poplar. | transgenic down-regulation of the pt4cl1 gene family encoding 4-coumarate:coenzyme a ligase (4cl) has been reported as a means for reducing lignin content in cell walls and increasing overall growth rates, thereby improving feedstock quality for paper and bioethanol production. using hybrid poplar (populus tremula × populus alba), we applied this strategy and examined field-grown transformants for both effects on wood biochemistry and tree productivity. the reductions in lignin contents obtained ... | 2010 | 20729393 |
| expression of the phytochelatin synthase tapcs1 in transgenic aspen, insight into the problems and qualities in phytoremediation of pb. | the response of populus tremula x tremuloides cv. etrepole transgenic lines expressing the phytochelatin synthase tapcs1 for pb tolerance and accumulation was studied. in a hydroponic experiment, the concentrations of pb in plants did not differ significantly between any of the transgenic lines assayed and the wild type (wt) plants, with any of the pb solutions tested. however, total biomass and pb accumulation were significantly higher in transgenic lines (pta3, pta5, pta10) than in the control ... | 2010 | 20734913 |
| genetic differentiation, clinal variation and phenotypic associations with growth cessation across the populus tremula photoperiodic pathway. | perennial plants monitor seasonal changes through changes in environmental conditions such as the quantity and quality of light. to ensure a correct initiation of critical developmental processes, such as the initiation and cessation of growth, plants have adapted to a spatially variable light regime and genes in the photoperiodic pathway have been implicated as likely sources for these adaptations. here we examine genetic variation in genes from the photoperiodic pathway in populus tremula (sal ... | 2010 | 20805554 |
| endogenous overexpression of populus myb186 increases trichome density, improves insect pest resistance, and impacts plant growth. | trichomes are specialized epidermal cells that generally play a role in reducing transpiration and act as a deterrent to herbivory. in a screen of activation-tagged populus tremula × populus alba 717-1b4 trees, we identified a mutant line, fuzzy, with increased foliar trichome density. this mutant also had a 35% increase in growth rate and a 200% increase in the rate of photosynthesis as compared with wild-type poplar. the fuzzy mutant had significant resistance to feeding by larvae of the white ... | 2010 | 20807210 |
| compartmentation of metals in foliage of populus tremula grown on soils with mixed contamination. i. from the tree crown to leaf cell level. | in order to achieve efficient phytoextraction of heavy metals using trees, the metal allocation to aboveground tissues needs to be characterised. in his study, the distribution of heavy metals, macro- and micronutrients and the metal micro-localisation as a function of the leaf position and heavy metal treatment were analysed in poplars grown on soil with mixed metal contamination. zinc was the most abundant contaminant in both soil and foliage and, together with cadmium, was preferentially accu ... | 2011 | 20822838 |
| transfer rna modifications and genes for modifying enzymes in arabidopsis thaliana. | in all domains of life, transfer rna (trna) molecules contain modified nucleosides. modifications to trnas affect their coding capacity and influence codon-anticodon interactions. nucleoside modification deficiencies have a diverse range of effects, from decreased virulence in bacteria, neural system disease in human, and gene expression and stress response changes in plants. the purpose of this study was to identify genes involved in trna modification in the model plant arabidopsis thaliana, to ... | 2010 | 20836892 |
| temperature response of isoprene emission in vivo reflects a combined effect of substrate limitations and isoprene synthase activity: a kinetic analysis. | the responses of isoprene emission rate to temperature are characterized by complex time-dependent behaviors that are currently not entirely understood. to gain insight into the temperature dependencies of isoprene emission, we studied steady-state and transient responses of isoprene emission from hybrid aspen (populus tremula × populus tremuloides) leaves using a fast-response gas-exchange system coupled to a proton-transfer reaction mass spectrometer. a method based on postillumination isopren ... | 2010 | 20837700 |
| growth regulators in populus tremula i. distribution of auxin and growth inhibitors. | the content of acid ether-soluble auxins and inhibitors in vegetative tissues of aspen (populus tremula l.) was determined with the avena coleoptile straightgrowth assay. a growth promotor, tentativety identified as indol-3-yl-acetic acid, occurred in highest concentration in the growing stem parts. it was also detected in various parts of the roots. large amounts of inhibitors (inhihitor β) were found in growing stem tissue and in upper mature stem parts. considerably lower content of inhibitor ... | 1969 | 20925679 |
| the triploid progeny of the cross diploid x tetraploid populus tremula. | | 1945 | 21021077 |
| chromosome numbers of the progeny from the cross triploid x tetraploid populus tremula. | | 1945 | 21021084 |
| differential impact of chronic ozone exposure on expanding and fully expanded poplar leaves. | populus tremula l. × populus alba l. (populus ×c anescens (aiton) smith) - clone inra 717-1-b4 saplings (50 cm apex to base and carrying 19 leaves on average) - were followed for 28 days. half of the trees were grown in charcoal-filtered air while the other half were exposed to 120 ppb ozone for 11 h a day during the light period. the expanding leaf number 4 was tagged at the beginning of the experiment and finished expansion between 7 and 14 days. these leaves were harvested weekly for biochemi ... | 2010 | 21030406 |
| xyloglucan endo-transglycosylase-mediated xyloglucan rearrangements in developing wood of hybrid aspen. | xyloglucan endo-transglycosylases (xets) encoded by xyloglucan endo-transglycosylases/hydrolase (xth) genes modify the xyloglucan-cellulose framework of plant cell walls, thereby regulating their expansion and strength. to evaluate the importance of xet in wood development, we studied xyloglucan dynamics and xth gene expression in developing wood and modified xet activity in hybrid aspen (populus tremula × tremuloides) by overexpressing ptxtxet16-34. we show that developmental modifications duri ... | 2010 | 21057113 |
| re-engineering specificity in 1,3-1, 4-β-glucanase to accept branched xyloglucan substrates. | family 16 carbohydrate active enzyme members bacillus licheniformis 1,3-1,4-β-glucanase and populus tremula x tremuloides xyloglucan endotransglycosylase (xet16-34) are highly structurally related but display different substrate specificities. although the first binds linear gluco-oligosaccharides, the second binds branched xylogluco-oligosaccharides. prior engineered nucleophile mutants of both enzymes are glycosynthases that catalyze the condensation between a glycosyl fluoride donor and a gly ... | 2011 | 21069723 |
| 1h, 13c, and 15n resonance assignments of reduced grxs14 from populus tremula × tremuloides. | grxs14 is a monothiol glutaredoxin (grx) from populus tremula × tremuloides, which has a cgfs active site. grxs14 is located in the chloroplasts and has been found to occur ether as an apo form or as a holo form with a [2fe-2s] cluster. the holo form contains two monomers of apo grxs14 bridged by the iron sulphur center, in the presence of two external glutathione molecules (bandyopadhyay et al. 2008). the nmr assignments of the grxs14 are essential for its solution structure determination. | 2010 | 21086077 |
| members of the lateral organ boundaries domain transcription factor family are involved in the regulation of secondary growth in populus. | regulation of secondary (woody) growth is of substantial economic and environmental interest but is poorly understood. we identified and subsequently characterized an activation-tagged poplar (populus tremula × populus alba) mutant with enhanced woody growth and changes in bark texture caused primarily by increased secondary phloem production. molecular characterization of the mutation through positioning of the tag and retransformation experiments shows that the phenotype is conditioned by acti ... | 2010 | 21097711 |
| successful hybridisation of normally incompatible hybrid aspen (populus tremula × p. tremuloides) and eastern cottonwood (p. deltoides). | hybrid aspen (populus tremula × p. tremuloides) belong to the section populus. eastern cottonwood (p. deltoides) is a member of the section aigeiros within the genus populus. these poplar sections are generally considered to be incompatible. here, we describe successful hybridisation between these parents, producing an offspring family with 27 individuals. the hybrid character of individuals was proven by genotypes at 16 nuclear microsatellite loci. one individual was suspected to have more than ... | 2010 | 21107610 |
| a single european aspen (populus tremula) tree individual may potentially harbour dozens of cenococcum geophilum its genotypes and hundreds of species of ectomycorrhizal fungi. | ectomycorrhizal fungi (ecmf) form diverse communities and link different host plants into mycorrhizal networks, yet little is known about the magnitude of mycobiont diversity of a single tree individual. this study addresses species richness and spatial structure of ecmf in the root system of a single european aspen (populus tremula) individual in an old-growth boreal mixed forest ecosystem in estonia. combining morphological and molecular identification methods for both plant and fungi, 122 spe ... | 2010 | 21114502 |
| photobiont association and genetic diversity of the optionally lichenized fungus schizoxylon albescens. | the fungus schizoxylon albescens occurs both as lichen and as saprobe. lichenized colonies grow on the bark of populus tremula; saprotrophic morphs grow on dead populus branches. we wanted to (1) test whether lichenized and saprotrophic s. albescens are genetically distinct, (2) investigate photobiont association and diversity, (3) investigate the interactions between fungi and algae that occur during co-cultivation and (4) test whether schizoxylon shows algal selectivity during lichenization. f ... | 2010 | 21133956 |
| trade-offs between biomass growth and inducible biosynthesis of polyhydroxybutyrate in transgenic poplar. | polyhydroxybutyrate (phb) is a bioplastic that can be produced in transgenic plants by the coexpression of three bacterial genes for its biosynthesis. phb yields from plants have been constrained by the negative impacts on plant health that result from diversion of resources into phb production; thus, we employed an ecdysone analogue-based system for induced gene expression. we characterized 49 insertion events in hybrid transgenic poplar (populus tremula x alba) that were produced using agrobac ... | 2011 | 21265995 |
| adaptive evolution of the populus tremula photoperiod pathway. | perennial plants monitor seasonal changes through changes in environmental conditions such as the quantity and quality of light and genes in the photoperiodic pathway are known to be involved in controlling these processes. here, we examine 25 of genes from the photoperiod pathway in populus tremula (salicaceae) for signatures of adaptive evolution. overall, levels of synonymous polymorphism in the 25 genes are lower than at control loci selected randomly from the genome. this appears primarily ... | 2011 | 21309875 |
| cell-specific chemotyping and multivariate imaging by combined ft-ir microspectroscopy and orthogonal projections to latent structures (opls) analysis reveals the chemical landscape of secondary xylem. | fourier-transform infrared (ft-ir) spectroscopy combined with microscopy enables chemical information to be acquired from native plant cell walls with high spatial resolution. combined with a 64 × 64 focal plane array (fpa) detector, 4096 spectra can be simultaneously obtained from a 0.3 × 0.3 mm image; each spectrum represents a compositional and structural 'fingerprint' of all cell wall components. for optimal use and analysis of such a large amount of information, multivariate approaches are ... | 2011 | 21332846 |
| ultra-structural organisation of cell wall polymers in normal and tension wood of aspen revealed by polarisation ftir microspectroscopy. | polarisation fourier transform infra-red (ftir) microspectroscopy was used to characterize the organisation and orientation of wood polymers in normal wood and tension wood from hybrid aspen (populus tremula × populus tremuloides). it is shown that both xylan and lignin in normal wood are highly oriented in the fibre wall. their orientation is parallel with the cellulose microfibrils and hence in the direction of the fibre axis. in tension wood a similar orientation of lignin was found. however, ... | 2011 | 21340698 |
| cellulose and lignin biosynthesis is altered by ozone in wood of hybrid poplar (populus tremula × alba). | wood formation in trees is a dynamic process that is strongly affected by environmental factors. however, the impact of ozone on wood is poorly documented. the objective of this study was to assess the effects of ozone on wood formation by focusing on the two major wood components, cellulose and lignin, and analysing any anatomical modifications. young hybrid poplars (populus tremula × alba) were cultivated under different ozone concentrations (50, 100, 200, and 300 l l(-1)). as upright poplars ... | 2011 | 21357770 |
| growth, leaf traits and litter decomposition of roadside hybrid aspen (populus tremula l.×p. tremuloides michx.) clones. | road traffic contributes considerably to ground-level air pollution and is therefore likely to affect roadside ecosystems. differences in growth and leaf traits among 13 hybrid aspen (populus tremula×p. tremuloides) clones were studied in relation to distance from a motorway. the trees sampled were growing 15 and 30m from a motorway and at a background rural site in southern finland. litter decomposition was also measured at both the roadside and rural sites. height and diameter growth rate and ... | 2011 | 21501910 |
| induction of a longer term component of isoprene release in darkened aspen leaves: origin and regulation under different environmental conditions. | after darkening, isoprene emission continues for 20 to 30 min following biphasic kinetics. the initial dark release of isoprene (postillumination emission), for 200 to 300 s, occurs mainly at the expense of its immediate substrate, dimethylallyldiphosphate (dmadp), but the origin and controls of the secondary burst of isoprene release (dark-induced emission) between approximately 300 and 1,500 s, are not entirely understood. we used a fast-response gas-exchange system to characterize the control ... | 2011 | 21502186 |
| a difference gel electrophoresis study on thylakoids isolated from poplar leaves reveals a negative impact of ozone exposure on membrane proteins. | populus tremula l. x p. alba l. (populus x canescens (aiton) smith), clone inra 717-1-b4, saplings were subjected to 120 ppb ozone exposure for 28 days. chloroplasts were isolated, and the membrane proteins, solubilized using the detergent 1,2-diheptanoyl-sn-glycero-3-phosphocholine (dhpc), were analyzed in a difference gel electrophoresis (dige) experiment comparing control versus ozone-exposed plants. extrinsic photosystem (ps) proteins and adenosine triphosphatase (atpase) subunits were detec ... | 2011 | 21520910 |
| can the capacity for isoprene emission acclimate to environmental modifications during autumn senescence in temperate deciduous tree species populus tremula? | changes in isoprene emission (φ(isoprene)), and foliage photosynthetic (a) rates, isoprene precursor dimethylallyldiphosphate (dmadp), and nitrogen and carbon contents were studied from late summer to intensive leaf fall in populus tremula to gain insight into the emission controls by temperature and endogenous, senescence-induced, modifications. methanol emissions, characterizing degradation of cell wall pectins, were also measured. a rapid reduction in φ(isoprene) and a of 60-70% of the initia ... | 2011 | 21584787 |
| genetic analysis of post-mating reproductive barriers in hybridizing european populus species. | molecular genetic analyses of experimental crosses provide important information on the strength and nature of post-mating barriers to gene exchange between divergent populations, which are topics of great interest to evolutionary geneticists and breeders. although not a trivial task in long-lived organisms such as trees, experimental interspecific recombinants can sometimes be created through controlled crosses involving natural f(1)'s. here, we used this approach to understand the genetics of ... | 2011 | 21587301 |
| functional and expressional analyses of pmdam genes associated with endodormancy in japanese apricot (prunus mume). | bud endodormancy in woody plants plays an important role in their perennial growth cycles. we previously identified a mads-box gene, prunus mume dormancy associated mads6 (pmdam6), expressed in the endodormant lateral buds of japanese apricot (p. mume) as a candidate for the dormancy-controlling gene. in this study, we demonstrated the growth inhibitory functions of pmdam6 by overexpressing it in transgenic poplar (populus tremula x tremuloides). transgenic poplar plants constitutively expressin ... | 2011 | 21795580 |
| uhplc-esi/tofms determination of salicylate-like phenolic gycosides in populus tremula leaves. | associations of salicylate-like phenolic glycosides (pgs) with biological activity have been reported in salix and populus trees, but only for a few compounds, and in relation to a limited number of herbivores. by considering the full diversity of pgs, we may improve our ability to recognize genotypes or chemotype groups and enhance our understanding of their ecological function. here, we present a fast and efficient general method for salicylate determination in leaves of eurasian aspen that us ... | 2011 | 21748301 |
| Overexpression of constitutively active Arabidopsis RabG3b promotes xylem development in transgenic poplars. | An Arabidopsis small GTPase, RabG3b, was previously characterized as a component of autophagy and as a positive regulator for xylem development in Arabidopsis. In this work, we assessed whether RabG3b modulates xylem-associated traits in poplar in a similar way as in Arabidopsis. We generated transgenic poplars (Populus alba × Populus tremula var. glandulosa) overexpressing a constitutively active form of RabG3b (RabG3bCA) and performed a range of morphological, histochemical and molecular analy ... | 2011 | 21895694 |
| temperature responses of dark respiration in relation to leaf sugar concentration. | changes in leaf sugar concentrations are a possible mechanism of short-term adaptation to temperature changes, with natural fluctuations in sugar concentrations in the field expected to modify the heat sensitivity of respiration. we studied temperature response curves of leaf dark respiration in the temperate tree populus tremula in relation to leaf sugar concentration i) under natural conditions, or ii) leaves with artificially enhanced sugar concentration. temperature response curves were obta ... | 2011 | 22188403 |
| tree and shrub expansion over the past 34 years at the tree-line near abisko, sweden. | shrubs and trees are expected to expand in the sub-arctic due to global warming. our study was conducted in abisko, sub-arctic sweden. we recorded the change in coverage of shrub and tree species over a 32- to 34-year period, in three 50 x 50 m plots; in the alpine-tree-line ecotone. the cover of shrubs and trees (<3.5 cm diameter at breast height) were estimated during 2009-2010 and compared with historical documentation from 1976 to 1977. similarly, all tree stems (> or =3.5 cm) were noted and ... | 2011 | 21954730 |
| molecular population genetics of elicitor-induced resistance genes in european aspen (populus tremula l., salicaceae). | owing to their long life span and ecological dominance in many communities, forest trees are subject to attack from a diverse array of herbivores throughout their range, and have therefore developed a large number of both constitutive and inducible defenses. we used molecular population genetics methods to examine the evolution of eight genes in european aspen, populus tremula, that are all associated with defensive responses against pests and/or pathogens, and have earlier been shown to become ... | 2011 | 21949772 |
| developmental changes in mesophyll diffusion conductance and photosynthetic capacity under different light and water availabilities in populus tremula: how structure constrains function. | finite mesophyll diffusion conductance (g(m) ) significantly constrains net assimilation rate (a(n) ), but g(m) variations and variation sources in response to environmental stresses during leaf development are imperfectly known. the combined effects of light and water limitations on g(m) and diffusion limitations of photosynthesis were studied in saplings of populus tremula l. an one-dimensional diffusion model was used to gain insight into the importance of key anatomical traits in determini ... | 2011 | 22070625 |
| influence of over-expression of the flowering promoting factor 1 gene (fpf1) from arabidopsis on wood formation in hybrid poplar (populus tremula l. × p. tremuloides michx.). | constitutive expression of the fpf1 gene in hybrid aspen (populus tremula l. × p. tremuloides michx.) showed a strong effect on wood formation but no effect on flowering time. gene expression studies showed that activity of flowering time genes ptft1, ptco2, and ptful was not increased in fpf1 transgenic plants. however, the soc1/tm3 class gene ptm5, which has been related to wood formation and flowering time, showed a strong activity in stems of all transgenic lines studied. wood density was lo ... | 2011 | 21909761 |
| photosynthetic acclimation to light in woody and herbaceous species: a comparison of leaf structure, pigment content and chlorophyll fluorescence characteristics measured in the field. | acclimation of foliage photosynthetic properties occurs with varying time kinetics, but structural, chemical and physiological factors controlling the kinetics of acclimation are poorly understood, especially in field environments. we measured chlorophyll fluorescence characteristics, leaf total carotenoid (car), chlorophyll (chl) and nitrogen (n) content and leaf dry mass per area (lma) along vertical light gradients in natural canopies of the herb species, inula salicina and centaurea jacea, a ... | 2012 | 21972867 |
| vertical profiles reveal impact of ozone and temperature on carbon assimilation of betula pendula and populus tremula. | rising temperature and tropospheric ozone (o(3)) concentrations are likely to affect carbon assimilation processes and thus the carbon sink strength of trees. in this study, we investigated the joint action of elevated ozone and temperature on silver birch (betula pendula) and european aspen (populus tremula) saplings in field conditions by combining free-air ozone exposure (1.2 × ambient) and infrared heaters (ambient +1.2 °c). at leaf level measurements, elevated ozone decreased leaf ne ... | 2011 | 21856655 |
| differential expression of specific sulphate transporters underlies seasonal and spatial patterns of sulphate allocation in trees. | sulphate uptake and its distribution within plants depend on the activity of different sulphate transporters (sultr). in long-living deciduous plants such as trees, seasonal changes of spatial patterns add another layer of complexity to the question of how the interplay of different transporters adjusts s distribution within the plant to environmental changes. poplar is an excellent model to address this question because its s metabolism is already well characterized. in the present study, the i ... | 2012 | 23278135 |
| constitutively elevated salicylic acid levels alter photosynthesis and oxidative state but not growth in transgenic populus. | salicylic acid (sa) has long been implicated in plant responses to oxidative stress. sa overproduction in arabidopsis thaliana leads to dwarfism, making in planta assessment of sa effects difficult in this model system. we report that transgenic populus tremula × alba expressing a bacterial sa synthase hyperaccumulated sa and sa conjugates without negative growth consequences. in the absence of stress, endogenously elevated sa elicited widespread metabolic and transcriptional changes that resemb ... | 2013 | 23903318 |
| lignin engineering in field-grown poplar trees affects the endosphere bacterial microbiome. | cinnamoyl-coa reductase (ccr), an enzyme central to the lignin biosynthetic pathway, represents a promising biotechnological target to reduce lignin levels and to improve the commercial viability of lignocellulosic biomass. however, silencing of the ccr gene results in considerable flux changes of the general and monolignol-specific lignin pathways, ultimately leading to the accumulation of various extractable phenolic compounds in the xylem. here, we evaluated host genotype-dependent effects of ... | 2016 | 26755604 |
| highly efficient transformation and regeneration of aspen plants through shoot-bud formation in root culture. | the natural capacity of aspen (populus tremula l.) roots for direct shoot-bud regeneration was harnessed to establish a highly efficient transformation and regeneration procedure that does not require a pre-selection stage on antibiotics. aspen stem segments were transformed using wildtype agrobacterium rhizogenes (lba9402) with the binary p35sgusint plasmid carrying the genes coding for β-glucuronidase (gus) and neomycin phosphotransferase ii. high levels of transient gus expression were found ... | 1996 | 24178519 |
| testing transgenic aspen plants with bar gene for herbicide resistance under semi-natural conditions. | obtaining herbicide resistant plants is an important task in the genetic engineering of forest trees. transgenic european aspen plants (populus tremula l.) expressing the bar gene for phosphinothricin resistance have been produced using agrobacterium tumefaciens-mediated transformation. successful genetic transformation was confirmed by pcr analysis for thirteen lines derived from two elite genotypes. in 2014-2015, six lines were evaluated for resistance to herbicide treatment under semi-natural ... | 2017 | 27437143 |
| transgenic poplars: expression of chimeric genes using four different constructs. | leaf or stem explants of a hybrid poplar clone (populus tremula x populus alba), sensitive to agrobacterium tumefaciens, were co-cultivated either by an octopine or a nopaline disarmed a. tumefaciens modified strain. transformed poplar shoots were readily regenerated from explants. the protocol was improved using the nopaline disarmed strain c58/pmp90 with the binary vector pbi121. this protocol was then used to test three other vectors. the first one, possessing a nptii gene fused to the camv 1 ... | 1992 | 24213546 |
| evolution, three-dimensional model and localization of truncated hemoglobin ptttrhb of hybrid aspen. | thus far, research on plant hemoglobins (hbs) has mainly concentrated on symbiotic and non-symbiotic hbs, and information on truncated hbs (trhbs) is scarce. the aim of this study was to examine the origin, structure and localization of the truncated hb (ptttrhb) of hybrid aspen (populus tremula l. × tremuloides michx.), the model system of tree biology. additionally, we studied the ptttrhb expression in relation to non-symbiotic class1 hb gene (ptthb1) using rnai-silenced hybrid aspen lines. bo ... | 2014 | 24520401 |