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At least 217 records · Page 12Linked to original sources
PubMed2007

High zinc concentrations reduce rooting capacity and alter metallothionein gene expression in white poplar (Populus alba L. cv. Villafranca).

Poplar is a good candidate for phytoremediation purposes because of its rapid growth, extensive root system, and ease of propagation and transformation; however its tolerance to heavy metals has not been fully investigated yet. In the present work, an in vitro model system with shoot cultures was used to investigate the tolerance to high concentrations of zinc (Zn) of a commercial clone (Villafranca) of Populus alba. Based on chlorophyll content (leaf chlorosis) and the rate of adventitious root formation from shoot cuttings as parameters of damage, 0.5-4mM zinc concentrations were all toxic albeit to different extents. Northern blot and reverse transcriptase (RT)-PCR analyses were used to examine the expression profiles of types 1, 2 and 3 PaMT genes in stems, leaves and roots of plants exposed to Zn treatments. In leaves, MT1 and MT3 mRNA levels were enhanced by Zn, while MT2 transcripts were not affected. The PaMT expression profiles were differentially affected by Zn in an organ-specific manner, and the relationship with Zn concentration and exposure time was rarely linear. The developmental and molecular data reveal that the in vitro model is a sensitive and reliable system to study heavy metal stress responses.

Biodegradation, Environmental↗
PubMed2005

NPH4/ARF7 and ARF19 promote leaf expansion and auxin-induced lateral root formation.

Auxin response factors (ARFs) bind auxin response promoter elements and mediate transcriptional responses to auxin. Five of the 22 ARF genes in Arabidopsis thaliana encode ARFs with glutamine-rich middle domains. Four of these can activate transcription and have been ascribed developmental functions. We show that ARF19, the fifth Q-rich ARF, also activates transcription. Mutations in ARF19 have little effect on their own, but in combination with mutations in NPH4/ARF7, encoding the most closely related ARF, they cause several phenotypes including a drastic decrease in lateral and adventitious root formation and a decrease in leaf cell expansion. These results indicate that auxin induces lateral roots and leaf expansion by activating NPH4/ARF7 and ARF19. Auxin induces the ARF19 gene, and NPH4/ARF7 and ARF19 together are required for expression of one of the arf19 mutant alleles, suggesting that a positive feedback loop regulates leaf expansion and/or lateral root induction.

Arabidopsis↗
PubMed1995

Arbuscular mycorrhizal induced changes to plant growth and root system morphology in Prunus cerasifera.

We compared root system morphogenesis of micropropogated transplants of Prunus cerasifera L. inoculated with either of the arbuscular mycorrhizal (AM) fungi Glomus mosseae or Glomus intraradices or with the ericoid mycorrhizal species Hymenoscyphus ericae. All plants were grown in sand culture, irrigated with a nutrient solution that included a soluble source of phosphorus, for 75 days after transplanting. Arbuscular mycorrhizal colonization increased both the survival and growth (by over 100%) of transplants compared with either uninoculated controls or transplants inoculated with H. ericae. Arbuscular mycorrhizal colonization increased root, stem and leaf weights, leaf area, root length and specific leaf area, and it decreased root length/leaf area ratio, root/shoot weight ratio and specific root length. Both uptake of phosphorus and its concentration in leaves were increased by AM infection, although the time course of the relationships between intensity of AM infection and P nutrition were complex and suggested a role for factors other than nutrition. The time course for the development of infection varied. It was most rapid with G. mosseae, but it was ultimately higher with G. intraradices. None of the treatments significantly affected the lengths of adventitious roots or the first-, second- or third-order laterals that developed from them. Arbuscular mycorrhizal colonization increased the intensity of branching in all root orders with the effect being most obvious on first-order lateral roots where the number of branches increased from under 100 to over 300 brances m(-1). As a result, although first-order laterals made up 55% of the root systems of control plants, the comparable value was 36% in AM-infected plants. In contrast, second-order laterals represented 25% of control root systems, but 50% of AM-colonized root systems. Glomus intraradices but not G. mosseae increased root diameter. Anatomical studies revealed no changes in the overall form of the root tip, although there were changes in the diameter of the root cap, cell numbers and cell size. Hymenoscyphus ericae increased the duration of the metaphase index. Both AM fungal treatments increased the concentrations of soluble proteins in root extracts and modified the protein profiles by the elimination and addition of protein bands detected by PAGE analysis. We conclude that AM fungal inoculation influenced processes in the root system at different levels, but not all effects were due to improved P nutrition or increased physiological age.

Journal Article↗
PubMed2001

Characterisation of the oxygen fluxes in the division, elongation and mature zones of Vitis roots: influence of oxygen availability.

Oxygen fluxes into and from root cells of Vitis rupestris (flooding sensitive), V. riparia (flooding tolerant) and V. vinifera (medium tolerance to flooding) were measured under different levels of O2 availability using a recently developed polarographic O2-selective, vibrating-microelectrode system. The system enables fluxes to be measured with a spatial resolution of 2-3 microm and a temporal resolution of 10 s. No difference in root porosity was found among the genotypes when grown for 30 days in an aerated solution. Under normoxic conditions, O2 influx was characterised by two distinct peaks, one in the division zone and the other in the elongation zone of the roots. This pattern was found in all three species studied, although the fluxes showed a different magnitude. The peak in the elongation zone coincided with maximum relative elemental growth rates. When the energetics of the cell was disturbed by cyanide, both growth and oxygen O2 influxes ceased at the same time. Under hypoxic conditions, V. riparia plants showed a precise strategy directed toward the maintenance of enough O2 for the respiratory needs of mitosis in the apical meristem of the roots. Thus, whereas in the division zone of V. rupestris and V. vinifera, at bulk O2 concentrations of 0.094 mol x m(-3), the O2 influx was reduced by 70.5 and 38.5%, respectively, for V. riparia no variation in the O2 influx was detected down to bulk O2 concentrations of 0.078 mol x m(-3). Moreover, in accordance with the different tolerances of the plants, the Vitis genotypes were found to differ in their radial O2 loss from the adventitious roots when in an O2-free environment. The results are discussed in terms of possible mechanisms of response to anoxia in Vitis species with different tolerances to flooding.

Adaptation, Physiological↗
PubMed2006

Rooting and vitality of poinsettia cuttings was increased by arbuscular mycorrhiza in the donor plants.

In this paper, we provide evidence that the rooting performance of cuttings can be improved by the arbuscular mycorrhizal (AM) symbiosis of donor plants. Poinsettia stock plants were inoculated with the Glomus intraradices isolate H510 and grown in three different cultivation systems (two organic and one conventional). AM colonization was not related to P availability in the substrate. Decay of the excised cuttings in response to unfavorable postharvest storage conditions was significantly reduced by AM colonization of the stock plants. In most cases, AM significantly promoted the formation of adventitious roots in the stored cuttings. The strongest effect of AM was found when donor plants were grown in a modified organic substrate; then AM-conditioned cuttings showed higher leaf sugar levels and a changed kinetic of carbohydrates during storage. Analyses of N, P, and K in cuttings did not indicate a nutritional effect. The results support the idea that an altered carbohydrate metabolism and plant hormones can contribute to improved rooting performance of cuttings excised from mycorrhizal donor plants.

Carbohydrates↗
PubMed1994

A molecular marker for lateral root initiation: the RSI-1 gene of tomato (Lycopersicon esculentum Mill) is activated in early lateral root primordia.

The frequency of lateral root initiation in tomato (Lycopersicon esculentum Mill cv. VFN8) seedling roots is increased over eightfold in response to 1.6 microM alpha-naphthalene-acetic acid (NAA). To identify genes that are activated during lateral root initiation, a cDNA library was made with RNA from roots treated with auxin and differentially screened with radioactive probes made from RNA isolated from treated and untreated roots. A cDNA clone, TR132, was identified that hybridized to a transcript that was induced within 4 h of auxin treatment and increased tenfold by 72 h. A gene (RSI-1) corresponding to the TR132 cDNA was cloned and characterized with regard to its nucleotide sequence, transcription start site and chromosomal map position. Approximately 1 kb of the 5' flanking DNA was linked to the beta-glucuronidase (GUS) protein coding region and tested for expression in transgenic tomato seedlings. GUS activity was observed in both lateral and adventitious root initials, including very early initials, and persisted until shortly after the lateral emerged from the parent tissue. In roots from seedlings with high activity, GUS expression was also observed in the root cap and vascular tissue. The predicted RSI-1 protein is rich in cysteine, lysine and proline, and includes an N-terminal region with characteristics of a signal peptide. The putative mature protein exhibits 79% amino acid identity to a protein encoded by a gene (GAST1) that is induced by gibberellic acid in tomato shoots.

Amino Acid Sequence↗
PubMed2002

Origin and basipetal transport of the IAA responsible for rooting of carnation cuttings.

The origin and transport of the IAA responsible for rooting was studied in carnation (Dianthus caryophyllus L.) cuttings obtained from secondary shoots of the mother plants. The presence of mature leaves in the cuttings was essential for rooting. Removal of the apex and/or the youngest leaves did not reduce the rooting percentage as long as mature leaves remained attached. Removal of mature leaves inhibited rooting for a 24-day period during which the basal leaves grew and reached maturity. After this period rooting progressed as in intact cuttings. Auxin (NAA + IBA) applied to the stem base of defoliated cuttings was about 60% as effective as mature leaves in stimulating rooting. Application of NPA to the basal internode resulted in full inhibition of rooting. The view, deduced from these results, that auxin from mature leaves is the main factor controlling the rooting process was reinforced by the fact that mature leaves contained IAA and exported labelled IAA to the stem. The distribution of radioactivity after application of (5-3H)-IAA to mature leaves showed that auxin movement in the stem was basipetal and sensitive to NPA inhibition. The features of this transport were studied by applying 3H-IAA to the apical cut surface of stem sections excised from cuttings. The intensity of the transport was lower in the oldest node than in the basal internode, probably due to the presence of vascular traces of leaves. Irrespective of the localization of the sections and the carnation cultivar used, basipetal IAA transport was severely reduced when the temperature was lowered from 25 to 4 degrees C. The polar nature of the IAA transport in the sections was confirmed by the inhibition produced by NPA. Local application of IAA to different tissues of the sections revealed that polar auxin transport was associated with the vascular cylinder, the transport in the pith and cortex being low and apolar. The present results strongly support the conclusion that IAA originating from the leaves and transported in the stem through the polar auxin transport pathway was decisive in controlling adventitious rooting.

Journal Article↗
PubMed2006

The diageotropica gene of tomato encodes a cyclophilin: a novel player in auxin signaling.

The single gene, auxin-resistant diageotropica (dgt) mutant of tomato displays a pleiotropic auxin-related phenotype that includes a slow gravitropic response, lack of lateral roots, reduced apical dominance, altered vascular development, and reduced fruit growth. Some auxin responses are unaltered in dgt plants, however, and the levels, metabolism, and transport of auxin appear normal, indicating that the Dgt gene encodes a component of a specific auxin signaling pathway. By combining map-based cloning with comparative microsynteny, we determined that the Dgt gene encodes a cyclophilin (CYP) (LeCYP1; gi:170439) that has not previously been identified as a component of auxin signaling and plant development. Each of the three known dgt alleles contains a unique mutation in the coding sequence of LeCyp1. Alleles dgt(1-1)and dgt(1-2) contain single nucleotide point mutations that generate an amino acid change (G137R) and a stop codon (W128stop), respectively, while dgt(dp) has an amino acid change (W128CDelta129-133) preceding a 15 bp deletion. Complementation of dgt plants with the wild-type LeCyp1 gene restored the wild-type phenotype. Each dgt mutation reduced or nullified the peptidyl-prolyl isomerase activity of the GST-LeCYP1 fusion proteins in vitro. RT-PCR and immunoblot analyses indicated that the dgt mutations do not affect the expression of LeCyp1 mRNA, but the accumulation of LeCYP1 protein is greatly reduced for all three mutant alleles. The CYP inhibitor, cyclosporin A, partially mimics the effects of the dgt mutation in inhibiting auxin-induced adventitious root initiation in tomato hypocotyl sections and reducing the auxin-induced expression of the early auxin response genes, LeIAA10 and 11. These observations confirm that the PPIase activity of the tomato CYP, LeCYP1, encoded by the Dgt gene is important for specific aspects of auxin regulation of plant growth, development, and environmental responses.

Alleles↗
PubMed1996

Structure of the dehydrin tas14 gene of tomato and its developmental and environmental regulation in transgenic tobacco.

We have isolated a genomic clone encoding tomato TAS14, a dehydrin that accumulates in response to mannitol, NaCl or abscisic acid (ABA) treatment. A fragment of tas14 gene containing the region from -2591 to +162 fused to beta-glucuronidase gene drives ABA- and osmotic stress-induced GUS expression in transgenic tobacco. Histochemical analysis of salt-, mannitol- and ABA-treated plants showed GUS activity mainly localized to vascular tissues, outer cortex and adventitious root meristems, coinciding with the previously observed distribution of TAS14 protein in salt-stressed tomato plants. In addition, GUS activity was also observed in guard cells, trichomes and leaf axils. Developmentally regulated gus expression was studied in unstressed plants and found to occur not only in embryos, but also in flowers and pollen. Tas14 expression in floral organs was confirmed by northern blots of tomato flowers.

Abscisic Acid↗
PubMed1993

A wound-induced promoter driving npt-II expression limited to dedifferentiated cells at wound sites is sufficient to allow selection of transgenic shoots.

There is much data to indicate that only a small number of cells in plant explants are competent for stable transformation by Agrobacterium. Circumstantial evidence suggests that certain cells reentering cell division at wound sites are competent for transformation by Agrobacterium. We have discovered a member of the intracellular PR gene family from asparagus (AoPR1) which is strongly expressed upon wounding and during the reactivation of the cell cycle in cultured asparagus cells, but which shows very little expression in intact plant tissues. The promoter from the AoPR1 gene was fused to an intron-containing GUS reporter gene and shown to be more strongly expressed than the commonly used CaMV 35S constitutive promoter in target cells for plant transformation. A transcriptional fusion of the AoPR1 promoter with an NPT-II gene was found to be a very efficient marker for the selection of transgenic tobacco callus. Expression of the AoPR1-NPT-II gene allowed efficient shoot formation on transgenic callus and efficient adventitious root formation on transgenic shoots. These latter observations provided firm evidence that transformation selection marker gene expression is most crucial at the early stages of the transformation process, during the establishment of transformed micro-calli.

Agrobacterium tumefaciens↗
PubMed2005

Enterobacter cloacae, an obligatory endophyte of pollen grains of Mediterranean pines.

Enterobacter cloacae was found to be associated with the pollen of several Mediterranean pines. The bacterium was detected only in mature pollen of Pinus halepensis, P. brutia, and P. pinea. E. cloacae is considered to be an obligatory endophyte based on its occurrence in disinfected male cones and the successful inoculation of seedlings of the above 3 species with E. cloacae AS1 isolated from pollen of P. halepensis used as a model strain. Strain AS1 was able to produce indolyl-3-acetic acid (IAA) from L-tryptophan in culture, and this was probably the source of the increased IAA content in the germination medium of pollen. In addition, strain AS1 promoted adventitious root formation in mung bean (Vigna radiata) cuttings. However, it was not possible to obtain bacterium-free pollen to elucidate its role in pollen germination.

Colony Count, Microbial↗
PubMed2002

Conservation and synteny of SSR loci and QTLs for vegetative propagation in four Eucalyptus species.

Conservation of microsatellite loci, heterozygous in Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus tereticornis and Eucalyptus globulus, allowed us to propose homeologies among genetic linkage groups in these species, supported by at least three SSR loci in two different linkage groups. Marker-trait associations for sprouting and adventitious rooting ability were also compared in the four species. Putative quantitative trait loci (QTLs) influencing vegetative propagation traits were located on homeologous linkage groups. Our findings indicate high transferability of microsatellite markers between Eucalyptus species of the Symphyomyrtus subgenus and establish foundations for the use of synteny in the genetic analysis of this genus. Microsatellite markers should help integrate eucalypt genetic linkage maps from various sources. The availability of comparative linkage maps provides a basis of more-efficient use of genetic information for molecular breeding and evolutionary studies in Eucalyptus.

Journal Article↗
PubMed1999

Water Level Effects on Growth of Melaleuca Seedlings from Lake Okeechobee (Florida, USA) Littoral Zone.

/ The invasive exotic wetland tree, Melaleuca quinquenervia, is expanding rapidly throughout seasonally wet areas of southern Florida (USA), including the littoral zone of Lake Okeechobee. Natural resource managers are concerned that a lower lake level regulation schedule under consideration for Lake Okeechobee, while potentially beneficial to overall ecosystem health, might increase the rate of Melaleuca expansion. To investigate this possibility, Melaleuca saplings (harvested from the littoral zone) and 7-week-old seedlings (grown from harvested seeds) were subjected to various hydroperiod treatments in replicated mesocosms. Hydroperiod treatments were selected based on a simulation of historical water level variations. Saplings grew taller under longer hydroperiods with fluctuating water levels, including periods of submersion. Time since germination affected the response of seedlings to inundation. Submersed 7-week-old seedlings grew slower and had less biomass than submersed 12-week-old seedlings, yet mortality was low at both ages. Melaleuca's plasticity allows it to adapt to hypoxic, aquatic conditions by means of aquatic heterophylly and adventitious roots. Algae and drought also increased mortality. Based on faster growth of Melaleuca under longer hydroperiods and its adaptability to seasonal flooding, a lower lake regulation schedule may not stimulate its expansion. Therefore, water levels should not be manipulated only to control Melaleuca. Control of Melaleuca should continue using current practices such as manual removal or chemical treatment. KEY WORDS: Melaleuca; Lake Okeechobee; Littoral zone; Water level; Regulation schedule

Journal Article↗
PubMed2000

Identification and expression of three new Nicotiana plumbaginifolia genes which encode isoforms of a plasma-membrane H(+)-ATPase, and one of which is induced by mechanical stress.

To analyze in detail the multigene family encoding the plasma-membrane H(+)-ATPase (pma) in Nicotiana plumbaginifolia Viv., five new pma genes (pma 5-9) were isolated. Three of these (pma 6, 8, 9) were fully characterized and classified into new and independent subfamilies. Their cell-type expression was followed by the beta-glucuronidase (gusA) reporter-gene method. While the pma8-gusA transgene was not expressed in transgenic tobacco, expression of the two other transgenes (pma6- and pma9-gusA) was found to be restricted to particular cell types. In the vegetative tissues, pma6-gusA expression was limited to the head cells of the leaf short trichomes, involved in secretion, and to the cortical parenchyma of the young nodes where the developing leaves and axillary flowering stalks join the stem. In the latter tissues, gene expression was enhanced by mechanical stress, suggesting that H(+)-ATPase might be involved in the strength of the tissues and their resistance to mechanical trauma. The pma9-gusA transgene was mainly expressed in the apical meristem of adventitious roots and axillary buds as well as in the phloem tissues of the stem, in which expression depended on the developmental stage. In flowers, pma9-gusA expression was limited to the mature pollen grains and the young fertilized ovules, while that of pma6-gusA was identified in most of the organs. Reverse transcription-polymerase chain reaction of leaf and stem RNA confirmed the expression of pma 6 and 9, while pma8 was found to be expressed in both organs at a lower level. In conclusion, although pma 6 and 9 had a more restricted expression pattern than the previously characterized pma genes, they were nevertheless expressed in cell types in which H(+)-ATPase had not been previously detected.

Cell Membrane↗
PubMed2006

Effects of copper sulfate and copper nitrate in aquatic medium on the restoration potential and accumulation of copper in stem cuttings of the terrestrial medicinal plant, Portulaca oleracea linn.

The stem cuttings of the terrestrial, ornamental plant, Portulaca oleracea, grew well in distilled water by producing adventitious roots and leaves. However, when exposed to various concentrations of sulfate and nitrate salts of copper resulted in a suppression of root growth, increase in initiation time of roots and sprouts and decay of stem cuttings from the cut open end, decrease in number of leaves with an increase in concentration of copper in the growth medium. Accumulation of copper increased with increasing concentrations of both copper sulfate and copper nitrate. However, copper accumulation was greater in copper nitrate than in copper sulfate treatment. Hence, copper in the presence of nitrate is more toxic than in the presence of sulfate. The accumulation factors in all treatment concentrations were greater than 1, hence P. oleracea is a copper accumulator.

Copper↗
PubMed2006

Pteris umbrosa R. Br. as an arsenic hyperaccumulator: accumulation, partitioning and comparison with the established As hyperaccumulator Pteris vittata.

The capacity of the Australian native fern Pteris umbrosa to function as an arsenic (As) hyperaccumulator (shoot:soil As concentration >1) was examined by growing plants under glasshouse conditions in an inert medium supplemented with As. Arsenic preferentially accumulated in the fronds, a trait of a hyperaccumulator. The As concentration of fronds decreased with age, being particularly high in the croziers and low in the senesced fronds. Below ground, rhizomes accumulated more As than adventitious roots. Uptake from a range of solution concentrations followed Michaelis Menten kinetics up to a soil solution As concentration of 400mgl(-1). The K(m) for As uptake by roots suggested the operation of a low-affinity carrier. The predicted Nernst membrane potential indicated that uptake was against the electrochemical gradient of As. At 600mgl(-1), the rate of As uptake increased and phytotoxic effects were indicated by a significant decline in biomass. Arsenic uptake and translocation in P. umbrosa and Pteris vittata were similar at low exposure to As. At higher exposure, As uptake and translocation by P. vittata increased more than in P. umbrosa. The growth rate of both ferns was similar, whereas the biomass distribution was not, with P. vittata having a much larger root mass. This suggests that As uptake by P. umbrosa roots was very efficient and may be improved by stimulating root growth to enhance its potential.

Arsenicals↗
PubMed2006

Analysis of dencichine in Panax notoginseng by gas chromatography-mass spectrometry with ethyl chloroformate derivatization.

Dencichine (beta-N-oxalyl-l-alpha,beta-diaminopropionic acid) is a haemostatic agent present in well-known traditional Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species. It is also a reported neurotoxic agent found in Lathyrus sativus (grass pea seed) and cycad seeds. A method was developed for quantitative determination of the non-protein amino acid, dencichine, in plant samples of P. notoginseng and the adventitious roots directly from the explants of P. notoginseng after derivatization with ethyl chloroformate (ECF) by gas chromatography-mass spectrometry (GC-MS). l-2-chlorophenylalanine was used as an internal standard. Calibration curves were linear (r(2)=0.9988, n=6) in the range of 10-800 microg/ml for dencichine. Limit of detection and quantification for dencichine were 0.5 microg/ml and 2 microg/ml, respectively. This rapid and specific method may be applied to the quantification of dencichine in complex medicinal plants and their products.

Amino Acids↗
PubMed2005

Control of plant development and gene expression by sugar signaling.

Coordination of development with the availability of nutrients, such as soluble sugars, may help ensure an adequate supply of building materials and energy with which to carry out specific developmental programs. For example, in-vivo and in-vitro experiments suggest that increasing sugar levels delay seed germination and stimulate the induction of flowering and senescence in at least some plant species. Higher sugar concentrations can also increase the number of tubers formed by potatoes and can stimulate the formation of adventitious roots by Arabidopsis. New insights into the mechanisms by which sugar-response pathways interact with other response pathways have been provided by microarray experiments examining sugar-regulated gene expression under different light and nitrogen conditions.

Carbohydrates↗