Characterization of spermidine binding to solubilized plasma membrane proteins from zucchini hypocotyls

Programmed Cell Death Reversal: Polyamines, Effectors of the U-Turn from the Program of Death in Helianthus tuberosus L

This review describes a 50-year-long research study on the characteristics of Helianthus tuberosus L. tuber dormancy, its natural release and programmed cell death (PCD), as well as on the ability to change the PCD so as to return the tuber to a life program. The experimentation on the tuber over the years is due to its particular properties of being naturally deficient in polyamines (PAs) during dormancy and of immediately reacting to transplants by growing and synthesizing PAs. This review summarizes the research conducted in a unicum body. As in nature, the tuber tissue has to furnish its storage substances to grow vegetative buds, whereby its destiny is PCD. The review's main objective concerns data on PCD, the link with free and conjugated PAs and their capacity to switch the destiny of the tuber from a program of death to one of new life. PCD reversibility is an important biological challenge that is verified here but not reported in other experimental models. Important aspects of PA features are their capacity to change the cell functions from storage to meristematic ones and their involvement in amitosis and differentiation. Other roles reported here have also been confirmed in other plants. PAs exert multiple diverse roles, suggesting that they are not simply growth substances, as also further described in other plants.

Polyamines: Α bioenergetic smart switch for plant protection and development

The present review highlights the bioenergetic role of polyamines in plant protection and development and proposes a universal model for describing polyamine-mediated stress responses. Any stress condition induces an excitation pressure on photosystem II by reforming the photosynthetic apparatus. To control this phenomenon, polyamines act directly on the molecular structure and function of the photosynthetic apparatus as well as on the components of the chemiosmotic proton-motive force (ΔpH/Δψ), thus regulating photochemical (qP) and non-photochemical quenching (NPQ) of energy. The review presents the mechanistic characteristics that underline the key role of polyamines in the structure, function, and bioenergetics of the photosynthetic apparatus upon light adaptation and/or under stress conditions. By following this mechanism, it is feasible to make stress-sensitive plants to be tolerant by simply altering their polyamine composition (especially the ratio of putrescine to spermine), either chemically or by light regulation.

Pre-harvest spray of GABA and spermine delays postharvest senescence and alleviates chilling injury of gerbera cut flowers during cold storage

Short vase life, capitulum wilting, neck bending, and postharvest chilling injury (CI) are major disorders have negative impact on quality and marketing of gerbera cut flowers. Low storage temperatures prolonging the vase life, but on the other hand leads serious CI which decreases the quality and consumer preferences. Spermine (SPER) and γ-aminobutyric acid (GABA) were identified as anti-aging factors delay the senescence and elevate the chilling tolerance in many species. Greenhouse-grown gerbera cv. 'Stanza' sprayed with 2 mM SPER and 1 mM GABA twice (2 T) or thrice (3 T). Cut flowers were stored at 1.5 °C and 8 °C postharvest to study the effects of GABA and SPER on senescence and CI. Vase life, CI and quality of cut flowers were improved by GABA and SPER treatments. No CI was observed in GABA-treated flowers at 1.5 °C; while, flowers sprayed with water showed severe CI. GABA treatments efficiently prolonged the vase life for 6-7 days more than the control (15 days). GABA and SPER increased the fresh weight, solution uptake, protein and proline contents, catalase, peroxidase, and superoxide dismutase activities, while decreased the electrolyte leakage, H₂O₂, and malondialdehyde contents, polyphenol oxidase, lipoxygenase, and phospholipase D activities. GABA and SPER significantly prolonged the vase life and prevented degradation of proteins and chilling damage and increased capacity of detoxifying and scavenging of H₂O₂ and reactive oxygen species (ROS), led to alleviate the negative consequences of the senescence and CI.

Polyamines induce adaptive responses in water deficit stressed cucumber roots

The aim of this study was to investigate the effect of exogenous polyamines (PAs) on the membrane status and proline level in roots of water stressed cucumber (Cucumis sativus cv. Dar) seedlings. It was found that water shortage resulted in an increase of membrane injury, lipoxygenase (LOX) activity, lipid peroxidation and proline concentration in cucumber roots during progressive dehydration. PA pretreatment resulted in a distinct reduction of the injury index, and this effect was reflected by a lower stress-evoked LOX activity increase and lipid peroxide levels at the end of the stress period. In contrast, PA-supplied stressed roots displayed a higher proline accumulation. The presented results suggest that exogenous PAs are able to alleviate water deficit-induced membrane permeability and diminish LOX activity. Observed changes were accompanied by an accumulation of proline, suggesting that the accumulation of this osmolyte might be another possible mode of action for PAs to attain higher membrane stability, and in this way mitigate water deficit effects in roots of cucumber seedlings.

Changes in free polyamine levels, expression of polyamine biosynthesis genes, and performance of rice cultivars under salt stress: a comparison with responses to drought

Soil salinity affects a large proportion of rural area and limits agricultural productivity. To investigate differential adaptation to soil salinity, we studied salt tolerance of 18 varieties of Oryza sativa using a hydroponic culture system. Based on visual inspection and photosynthetic parameters, cultivars were classified according to their tolerance level. Additionally, biomass parameters were correlated with salt tolerance. Polyamines have frequently been demonstrated to be involved in plant stress responses and therefore soluble leaf polyamines were measured. Under salinity, putrescine (Put) content was unchanged or increased in tolerant, while dropped in sensitive cultivars. Spermidine (Spd) content was unchanged at lower NaCl concentrations in all, while reduced at 100 mM NaCl in sensitive cultivars. Spermine (Spm) content was increased in all cultivars. A comparison with data from 21 cultivars under long-term, moderate drought stress revealed an increase of Spm under both stress conditions. While Spm became the most prominent polyamine under drought, levels of all three polyamines were relatively similar under salt stress. Put levels were reduced under both, drought and salt stress, while changes in Spd were different under drought (decrease) or salt (unchanged) conditions. Regulation of polyamine metabolism at the transcript level during exposure to salinity was studied for genes encoding enzymes involved in the biosynthesis of polyamines and compared to expression under drought stress. Based on expression profiles, investigated genes were divided into generally stress-induced genes (ADC2, SPD/SPM2, SPD/SPM3), one generally stress-repressed gene (ADC1), constitutively expressed genes (CPA1, CPA2, CPA4, SAMDC1, SPD/SPM1), specifically drought-induced genes (SAMDC2, AIH), one specifically drought-repressed gene (CPA3) and one specifically salt-stress repressed gene (SAMDC4), revealing both overlapping and specific stress responses under these conditions.

Cadaverine: a lysine catabolite involved in plant growth and development

The cadaverine (Cad) a diamine, imino compound produced as a lysine catabolite is also implicated in growth and development of plants depending on environmental condition. This lysine catabolism is catalyzed by lysine decarboxylase, which is developmentally regulated. However, the limited role of Cad in plants is reported, this review is tempted to focus the metabolism and its regulation, transport and responses, interaction and cross talks in higher plants. The Cad varied presence in plant parts/products suggests it as a potential candidate for taxonomic marker as well as for commercial exploitation along with growth and development.

Postharvest polyamine application alleviates chilling injury and affects apricot storage ability

Fruit of two apricot cultivars 'Bagheri' and 'Asgarabadi' were treated with putrescine (Put) or spermidine (Spd) at 1 mM and then were stored at 1 °C for 21 days. Fruit were sampled weekly and stored 2 days at 20 °C for shelf-life study. The treatments reduced ethylene production and maintained the firmness and color of the fruit. Peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), and polyphenol oxidase (PPO) activities and total phenol (TP) concentrations were measured during storage. Both cultivars showed chilling injury (CI) incidence, and the severity in control fruit was higher than either Put or Spd treatments. CI incidence in Spd-treated fruit was lower than that of Put-treated fruit. Polyamine (PA) treatment generally increased antioxidant enzyme activity of fruit during storage. PA treatments may help maintain the quality of apricot fruit during storage by inhibiting ripening and decreasing CI incidence.

Characteristics of cellular polyamine transport in prokaryotes and eukaryotes

Polyamine content in cells is regulated by biosynthesis, degradation and transport. In Escherichia coli, there are two polyamine uptake systems, namely spermidine-preferential (PotABCD) and putrescine-specific (PotFGHI), which belong to the family of ATP binding cassette transporters. Putrescine-ornithine and cadaverine-lysine antiporters, PotE and CadB, each consisting of 12 transmembrane segments, are important for cell growth at acidic pH. Spermidine excretion protein (MdtJI) was also recently identified. When putrescine was used as energy source, PuuP functioned as a putrescine transporter. In Saccharomyces cerevisiae, there are four kinds of polyamine uptake proteins (DUR3, SAM3, GAP1 and AGP2), consisting of either 12 or 16 transmembrane segments. Among them, DUR3 and SAM3 mostly contribute to polyamine uptake. There are also five kinds of polyamine excretion proteins (TPO1-5), consisting of 12 transmembrane segments. Among them, TPO1 and TPO5 are the most active proteins. Since a polyamine metabolizing enzyme, spermidine/spermine N(1)-acetyltransferase, is not present in yeast, five kinds of excretion proteins may exist. The current status of polyamine transport in mammalian and plant cells are reviewed.

Polyamines: molecules with regulatory functions in plant abiotic stress tolerance

Early studies on plant polyamine research pointed to their involvement in responses to different environmental stresses. During the last few years, genetic, transcriptomic and metabolomic approaches have unravelled key functions of different polyamines in the regulation of abiotic stress tolerance. Nevertheless, the precise molecular mechanism(s) by which polyamines control plant responses to stress stimuli are largely unknown. Recent studies indicate that polyamine signalling is involved in direct interactions with different metabolic routes and intricate hormonal cross-talks. Here we discuss the integration of polyamines with other metabolic pathways by focusing on molecular mechanisms of their action in abiotic stress tolerance. Recent advances in the cross talk between polyamines and abscisic acid are discussed and integrated with processes of reactive oxygen species (ROS) signalling, generation of nitric oxide, modulation of ion channel activities and Ca(2+) homeostasis, amongst others.

Polyamines: molecules with regulatory functions in plant abiotic stress tolerance

Early studies on plant polyamine research pointed to their involvement in responses to different environmental stresses. During the last few years, genetic, transcriptomic and metabolomic approaches have unravelled key functions of different polyamines in the regulation of abiotic stress tolerance. Nevertheless, the precise molecular mechanism(s) by which polyamines control plant responses to stress stimuli are largely unknown. Recent studies indicate that polyamine signalling is involved in direct interactions with different metabolic routes and intricate hormonal cross-talks. Here we discuss the integration of polyamines with other metabolic pathways by focusing on molecular mechanisms of their action in abiotic stress tolerance. Recent advances in the cross talk between polyamines and abscisic acid are discussed and integrated with processes of reactive oxygen species (ROS) signalling, generation of nitric oxide, modulation of ion channel activities and Ca(2+) homeostasis, amongst others.

The polycyclic aromatic hydrocarbon phenanthrene causes oxidative stress and alters polyamine metabolism in the aquatic liverwort Riccia fluitans L

The polycyclic aromatic hydrocarbon (PAH) phenanthrene (PHEN) is a highly toxic pollutant, commonly found in aquatic environments, the effects of which on aquatic plants have not been studied in depth. As PAHs are known to induce oxidative stress and recent studies have shown that polyamines (PAs) participate in the defence reactions protecting plants against environmental stresses, PA metabolism and oxidative damage were investigated in the aquatic form of the liverwort Riccia fluitans L. exposed to PHEN. Exposure of Riccia fluitans plants to PHEN at concentrations of 0.5 microm or less induced oxidative stress, but at a level from which plants could recover. Despite increased levels of enzymatic and non-enzymatic antioxidants, recovery appeared, at least in part, due to increased synthesis of PAs, achieved via increased activities of the enzymes arginine decarboxylase (ADC) and S-adenosylmethionine decarboxylase (SAMDC). Chemical inhibition of these enzymes inhibited plant recovery, while treatment with PAs aided recovery. Finally, as chloroplasts and the plasma membrane appeared to be key targets for PHEN-induced damage, the potential roles of PAs in protecting these cellular components were considered. How PAs could protect plant cells from serious environmental pollutants such as PHEN and could prevent oxidative stress is discussed.

Polyamines improve K+/Na+ homeostasis in barley seedlings by regulating root ion channel activities

Polyamines are known to increase in plant cells in response to a variety of stress conditions. However, the physiological roles of elevated polyamines are not understood well. Here we investigated the effects of polyamines on ion channel activities by applying patch-clamp techniques to protoplasts derived from barley (Hordeum vulgare) seedling root cells. Extracellular application of polyamines significantly blocked the inward Na(+) and K(+) currents (especially Na(+) currents) in root epidermal and cortical cells. These blocking effects of polyamines were increased with increasing polycation charge. In root xylem parenchyma, the inward K(+) currents were blocked by extracellular spermidine, while the outward K(+) currents were enhanced. At the whole-plant level, the root K(+) content, as well as the root and shoot Na(+) levels, was decreased significantly by exogenous spermidine. Together, by restricting Na(+) influx into roots and by preventing K(+) loss from shoots, polyamines were shown to improve K(+)/Na(+) homeostasis in barley seedlings. It is reasonable to propose that, therefore, elevated polyamines under salt stress should be a self-protecting response for plants to combat detrimental consequences resulted from imbalance of Na(+) and K(+).

Interaction of spermine with a signal transduction pathway involving phospholipase C, during the growth of Catharanthus roseus transformed roots

In Cantharanthus roseus transformed roots, the application of methylglyoxal bis(guanylhydrazone) (MGBG), an inhibitor of S-adenosylmethionine decarboxylase (SAMDC; EC 4.1.1.50), inhibited the root growth in a dose-dependent manner with a DL(50) of about 300 micro m. Spermidine and spermine (Spm) levels and SAMDC and phospholipase C (PLC; EC 3.1.4.3) activities were reduced in the presence of the inhibitor. The inhibition was reversed by the addition of Spm. Radioactivity from [(14)C]Spm was detected in an immunoprecipitated fraction with an antibody anti-PLC-delta. To our knowledge, this is the first direct evidence that demonstrates an interaction of Spm with the signal transduction cascade phosphoinositide-Ca(2+).

Ectomycorrhizal fungal species and strains differ in their ability to produce free and conjugated polyamines

Production of free and conjugated polyamines by one strain of Laccaria proxima (Boud.) Maire, three strains (H, O, K) of Paxillus involutus (Batsch) Fr., and one strain of Pisolithus tinctorius was studied in vitro. Spermidine (Spd) was the main polyamine in the 4-week-old mycelium of all the fungi. It was mainly present in the free form, but it also occurred in conjugated forms. Paxillus involutus strain H released large amounts of free putrescine (Put), and the Pisolithus tinctorius released a compound probably related to cadaverine (Cad). On the other hand, these two fungi contained less conjugated polyamines than the other fungi. In addition to the amounts, the forms (perchloric acid soluble and insoluble) of conjugated polyamines in the mycelium varied between species and strains. L. proxima contained nearly as much insoluble conjugated Spd as free Spd, whereas Paxillus involutus strains O and K contained relatively large amounts of soluble conjugated Spd. The results suggest that ectomycorrhizal fungal species and strains differ in their ability and need to produce conjugated polyamines. The small amounts of soluble conjugated polyamines found in the culture filtrates indicate that some specific conjugated polyamines may be involved in polyamine translocation across the plasma membrane.

Effect of infiltrated polyamines on polygalacturonase activity and chilling injury responses in zucchini squash (Cucurbita pepo L.)

The effect of exogenous polyamines on electrolyte leakage, chilling index, polygalacturonase activity (PG), ethylene production, and firmness in zucchini squash fruits stored for 12 days at 2 degrees C or 10 degrees C, 85-90% RH was evaluated. Fruits were infiltrated with putrescine (PUT) spermidine (SPD) and spermine (SPM) at 0.1, 0.25, 0.5, 2.0, and 4.0 mM. All polyamines exerted a protective effect on cell and organelle membranes. The most effective was SPD, which reduced electrolyte leakage between 62% and 82%, compared to control fruits stored at 2 degrees C. At 10 degrees C they did not exhibit chilling injury (CI) symptoms, while at 2 degrees C SPM (0.5 mM) and SPD (0.5 mM) diminished them 92% and 100%, respectively; which extended storage life for 8-10 days at 2 degrees C. High concentrations of polyamines (>2.0 mM) caused the appearance of CI symptoms. PG activity diminished proportionally to the concentration of polyamine except for the concentration at 4.0 mM. No significant changes were observed in ethylene production.

Spermidine-binding proteins. Purification and expression analysis in maize

Polyamine-binding proteins have been identified in a wide range of organisms, including mammals, yeasts, and bacteria. In this work, we have investigated specific spermidine binding to plant membrane proteins purified from microsomes of etiolated maize (Zea mays) coleoptiles. In the final purification step, specific spermidine-binding activity (K(d) 6.02 10(-7) M) was eluted from a HiTrapQ fast-protein liquid chromatography column at about 0.25 M NaCl, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the most active fraction showed a major polypeptide of about 60 kD and another copurifying 18-kD protein. Competition experiments, performed on HiTrapQ active fractions, confirmed the specificity of the binding. Upon Sephadex G-100 gel filtration, spermidine binding was associated almost exclusively with the 18-kD protein. On the basis of the N-terminal sequences, degenerate oligonucleotide probes were designed and used to isolate, by reverse transcriptase-polymerase chain reaction and polymerase chain reaction, cDNA fragments of about 1 kb for the 60-kD protein, and 0.9 kb for the 18-kD protein. Northern-blot analysis performed on etiolated coleoptiles and different tissues from 10-d-old maize plants indicated the presence of two different mRNAs of 1.7 and 0.7 kb. Southern-blot analysis indicated that the genes encoding the 60- and 18-kD proteins are probably derived from differential processing of the same precursor mRNA. Using rabbit polyclonal antibodies raised against these proteins, affinity purification and dot-blot experiments detected analogous membrane proteins in monocot and dicot plants.

Divalent cations and polyamines bind to loop 8 of 14-3-3 proteins, modulating their interaction with phosphorylated nitrate reductase

Binding of 14-3-3 proteins to nitrate reductase phosphorylated on Ser543 (phospho-NR) inhibits activity and is responsible for the inactivation of nitrate reduction that occurs in darkened leaves. The 14-3-3-dependent inactivation of phospho-NR is known to require millimolar concentrations of a divalent cation such as Mg2+ at pH 7.5. We now report that micromolar concentrations of the polyamines, spermidine(4+) and spermine(3+), can substitute for divalent cations in modulating 14-3-3 action. Effectiveness of the polyamines decreased with a decrease of polycation charge: spermine(4+) > spermidine(3+) >>> cadavarine(2+) approximately putrescine(2+) approximately agmatine(2+) approximately N1-acetylspermidine(2+), indicating that two primary and at least one secondary amine group were required. C-terminal truncations of GF14 omega, which encodes the Arabidopsis 14-3-3 isoform omega, indicated that loop 8 (residues 208-219) is the likely cation-binding site. Directed mutagenesis of loop 8, which contains the EF hand-like region identified in earlier studies, was performed to test the role of specific amino acid residues in cation binding. The E208A mutant resulted in a largely divalent cation-independent inhibition of phospho-NR activity, whereas the D219A mutant was fully Mg(2+)-dependent but had decreased affinity for the cation. Mutations and C-terminal truncations that affected the Mg(2+) dependence of phospho-NR inactivation had similar effects on polyamine dependence. The results implicate loop 8 as the site of divalent cation and polyamine binding, and suggest that activation of 14-3-3s occurs, at least in part, by neutralization of negative charges associated with acidic residues in the loop. We propose that binding of polyamines to 14-3-3s could be involved in their regulation of plant growth and development.

Polyamine metabolism is upregulated in response to tobacco mosaic virus in hypersensitive, but not in susceptible, tobacco

•  Change is reported in the biosynthetic and oxidative activity of hypersensitive (NN) and susceptible (nn) tobacco (Nicotiana tabacum) plants in response to tobacco mosaic virus (TMV). •  Mature leaves of nn and NN tobacco were collected over 0-72 h as uninoculated controls or after inoculation with TMV or phosphate buffer (mock-inoculation). The polyamine response to inoculation was analysed by measuring activity and gene expression of S-adenosylmethionine decarboxylase (SAMDC), arginine-(ADC) and ornithine decarboxylases (ODC); incorporation of labelled putrescine; and activity of diamine oxidase (DAO). •  In NN leaves SAMDC activity and transcript levels, and DAO activity increased in the TMV-inoculated plants but not in the other treatments; a two-fold increase in DAO activity was seen after 72 h. Both ADC and ODC activity increased in NN leaves at 72 h in TMV-inoculated plants; ADC mRNA increased with activity. The increase in SAMDC mRNA (24 h) preceded the rise in activity (72 h). [³ H]putrescine added to NN leaves led to enhanced label recovery and incorporation into spermidine and spermine in TMV-inoculated plants. No significant changes in biosynthetic or oxidative activity occurred in nn plants. •  After TMV inoculation, NN, unlike nn, tobacco plants upgrade polyamine synthesis and oxidation; this leads to changes in cellular components which might induce programmed cell death.