1,721,015 research outputs found
Analisi d’espressione dei geni MT (Metallotioneine) in un clone di pioppo tollerante i metalli cresciuto su terreno inquinato da Cu e Zn.
No full textDownregulation of ethylene production and biosynthetic gene expression is associated to changes in putrescine metabolism in shoot-forming tobacco thin layers.
No full textThe effect of aminoethoxyvinylglycine (AVG), an inhibitor of 1-aminocyclopropane-1-carboxylate synthase (ACS) activity, on
ethylene emission and biosynthetic gene expression, on gene expression and/or activity of polyamine (putrescine, spermidine and spermine) biosynthetic enzymes, and on diamine oxidase (DAO, EC 1.4.3.6) activity was evaluated in tobacco (Nicotiana tabacum L. cv. Samsun) thin layers cultured on a shoot-forming medium (1 mM indol-3-acetic acid (IAA) plus 10 mM benzyladenine (BA)). Northern analyses showed that ACS and 1-aminocyclopropane-1-carboxylate oxidase (ACO) transcripts were present throughout culture with a maximum accumulation on day 7. Besides ethylene emission, AVG (0.5 mM) increasingly reduced ACS and ACO messages. The time course of labelled methionine incorporation into spermidine and spermine, which share with ethylene the common precursor S-adenosylmethionine (SAM), as well as SAM decarboxylase (SAMDC, EC 4.1.1.21) activity and gene expression, were not affected by AVG treatment. On the contrary, labelled putrescine incorporation into the higher polyamines
(spermidine and spermine) and into trichloroacetic acid (TCA)-soluble polyamine conjugates was enhanced early in culture (day 2) by the drug. Putrescine biosynthetic enzyme activities, arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17), were also increased in AVG-treated explants. Moreover, inhibition of ethylene synthesis by AVG led to a strong reduction in diamine oxidising activity, especially the one associated with a cell wall-enriched fraction. Changes in putrescine biosynthesis, oxidation and flux into higher polyamines are discussed in the light of the rejuvenating effect of AVG
Polyamine conjugation during the cell cycle of Helianthus tuberosus: non enzymatic and transglutaminase-like binding activity
No full textParenchyma cells of Helianthus tuberosus tuber slices were activated with 2,4-dichlorophenoxyacetic acid in order to induce a synchronous cell cycle. In vivo polyamine conjugation during the cell cycle was studied by activating the slices in a medium containing [14C]putrescine. In vitro polyamine conjugates were obtained by incubating activated slice extracts with both [3H]- and [14C]putrescine as tracers. Different methods of isolation of the conjugates were assayed. Two different putrescine binding activities have been found: a temperature-sensitive one (possibly a transglutaminase-like activity) which, after an early decrease, rose in late G1-early S phase and then remained constant, and a temperature-insensitive activity which slowly increased during the cycle. A thin layer chromatography analysis, after acid hydrolysis, of the in vitro conjugates showed that the main bound polyamine was putrescine; other derivatives, in different percentages according to the type of labelled precursor used, were also found. Sodium dodecylsulphate polyacrylamide gel electrophoresis fluorograms showed that with both labels, heavy molecular weight conjugates were obtained both in vivo and in vitro that cannot enter the running gel; they were more stable when produced by the temperature-sensitive activity. Many [14C]putrescine conjugates of lower molecular weight were also found by the in vitro assay
Rhizogenesis from tobacco thin layers: effects of various inhibitors of polyamine biosynthesis.
No full textAnalisi d’espressione dei geni MT (Metallotioneine) in un clone di pioppo tollerante i metalli cresciuto su terreno inquinato da Cu e Zn
No full text
Effetti di alte concentrazioni di rame e zinco sull’espressione genica delle metallotioneine, sul complemento di poliammine e sulla rizogenesi di Populus alba L. in micropropagazione.
No full textEpigenetic control of heavy metal stress response in mycorrhizal versus non-mycorrhizal poplar plants
No full textIt was previously shown that arbuscular mycorrhizal
fungi (AMF) exert a significant improvement of growth in
a tolerant white poplar (Populus alba L.) clone (AL35) grown
on Cu- and Zn-polluted soil via foliar alterations in the levels
of defence/stress-related transcripts and molecules. However,
nothing is known about the epigenetic changes which occur
during tolerance acquisition in response to heavy metals
(HMs) in the same mycorrhizal vs. non-mycorrhizal poplar
plants. In order to analyse the epigenome in leaves of AL35
plants inoculated or not withAMF and grown in a greenhouse
on multimetal polluted or unpolluted soil, the Methylation
Sensitive Amplification Polymorphism (MSAP) approach
was adopted to detect cytosine DNA methylation. Modest
changes in cytosine methylation patterns were detected at first
sampling (4 months from planting), whereas extensive alterations
(hypomethylation) occurred at second sampling (after
6 months) in mycorrhizal plants grown in the presence of
HMs. The sequencing of MSAP fragments led to the identification of genes belonging to several Gene Ontology
categories. Seven MSAP fragments, selected on the basis of
DNA methylation status in treated vs control AL35 leaves at
the end of the experiment, were analysed for their transcript
levels by means of qRT-PCR. Gene expression varied in
treated samples relative to controls in response to HMs and/
or AMF inoculation; in particular, transcripts of genes involved
in RNA processing, cell wall and amino acid metabolism
were upregulated in the presence ofAMF with or without
HMs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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