Role of Polyamines in Apoptosis and Other Recent Advances in Plant Polyamines

Numerous citations in the literature indicate that polyamines are intensively studied in plants. Polyamines are implicated in many functions of the plant cell. Excellent recent reviews cover much of this original research. This article is focused primarily on literature that relates research on the role of polyamines in apoptosis and programmed cell death in both plants and animals. Apoptosis and programmed cell death are considerably better studied in animal systems, and this review demonstrates that the role of polyamines in these processes in plant systems are remarkably congruent with what is known in animal systems. In addition, key recent research reports are reviewed that describe the functional analysis of key polyamine biosynthesis genes in plants in relation to responses to environmental stress signals. Molecular analysis is providing strong evidence for the polyamine biosynthetic pathways to play major roles in ameliorating plant responses to abiotic stresses.     

Polyamines in Entamoeba invadens

The polyamine content of Entamoeba was measured by a procedure that involved benzoylation followed by high performance liquid chromatography (h.p.l.c.). A high concentration of putrescine and significant amounts of spermidine and spermine were found in actively growing trophozoites and in the cyst forms of the organism. In contrast, trophozoites in stationary phase had greatly reduced amounts of putrescine and exhibited peaks in h.p.l.c., possibly indicative of acetylated polyamines. alpha-D,L-difluoromethylornithine (DFMO) lowered the concentration of polyamines in growing trophozoites, but did not inhibit the degree of proliferation. There is evidence for pathways of polyamine biosynthesis in Entamoeba other than through ornithine decarboxylase (ODC).     

Polyamines in intestinal growth

The total cellular mass of the small intestine is well controlled and can adapt, with hypo- or hyperplasia, to a wide variety of stimuli. Luminal nutrients, hormonal factors and pancreatic and biliary secretions have all been implicated in the regulation of intestinal mucosal growth. The polyamines (putrescine, spermidine and spermine) and the key enzyme controlling their synthesis (ornithine decarboxylase. ODC) are critical for many cell growth processes and appear to play important roles in intestinal growth. During intestinal adaptation in response to jejunectomy, lactation. pancreatic-biliary diversion, starvation-refeeding and feeding with kidney bean lectin, intestinal contents of ODC and polyamines are increased, paralleling increases in mucosal proliferative indices and DNA synthesis. With administration of the specific inhibitor of ODC (difluoromethylornithine, DFMO) the increase in ODC and polyamines is inhibited and intestinal growth is suppressed. In addition, the oral administration of exogenous polyamines results in precocious maturation of the neonatal rat intestine. These results suggest that the polyamines are important for intestinal growth.     

Polyamines in trypanosomatids.

Polyamines were determined by n-butanol extraction and thin-layer chromatography in four trypanosomatids: Trypanosoma brucei (rat infection) and cultures of Crithidia fasciculata, Leptomonas sp., and Trypanosoma mega. All had putrescine and spermidine but no detectable spermine. Putrescine and spermidine levels were quantitated for extracts of leptomonas during the normal growth cycle. Spermidine values peaked 18 h before peak cell populations. Spermidine-putrescine ratios for all organisms were related to the presumed phylogeny of the group.     

Polyamines in renal failure

Summary. The levels of polyamines (putrescine, spermidine and spermine) and polyamine oxidase in plasma of patients with chronic renal failure were determined. The level of putrescine was increased but the level of spermine was decreased in the plasma of these patients. The patients also had increased plasma polyamine oxidase activity leading to increased degradation of spermine. As acrolein was a major toxic compound produced from spermine by polyamine oxidase, the levels of free and protein-conjugated acrolein in plasma were also measured. Acrolein levels were enhanced in plasma of patients with chronic renal failure. The accumulated acrolein found as protein conjugates was equivalent to 170 μM, which was about 5-fold higher than in plasma of normal subjects. It was found that acrolein is mainly produced by spermine oxidase in plasma. An increase in putrescine, spermine oxidase and acrolein in plasma was observed in all cases such as diabetic nephropathy, chronic glomerulonephritis and nephrosclerosis. After patients with chronic renal failure had undergone hemodialysis, their levels of plasma polyamines, spermine oxidase and acrolein returned towards normal. It is likely that acrolein produced from spermine accumulates in the blood due to decreased excretion into urine and may function as a uremic “toxin”.     

Polyamines in halophilic archaebacteria

Abstract The presence of stable mRNA in domant spores of several Streptomyces species is reported. The proteins encoded by these mRNAs are remarkably similar in all the species studied. A high degradation rate during the first hour of germination is a common feature to these proteins.     

Polyamines in plant physiology

The diamine putrescine, the triamine spermidine, and the tetramine spermine are ubiquitous in plant cells, while other polyamines are of more limited occurrence. Their chemistry and pathways of biosynthesis and metabolism are well characterized. They occur in the free form as cations, but are often conjugated to small molecules like phenolic acids and also to various macromolecules. Their titer varies from approximately micromolar to more than millimolar, and depends greatly on environmental conditions, especially stress. In cereals, the activity of one of the major polyamine biosynthetic enzymes, arginine decarboxylase, is rapidly and dramatically increased by almost every studied external stress, leading to 50-fold or greater increases in putrescine titer within a few hours. The physiological significance of this increase is not yet clear, although most recent work suggests an adaptive, protective role. Polyamines produced through the action of ornithine decarboxylase, by contrast, seem essential for DNA replication and cell division. The application of exogenous polyamines produces effects on patterns of senescence and morphogenesis, suggesting but not proving a regulatory role for polyamines in these processes. The evidence for such a regulatory role is growing.     

Polyamines in dimorphic fungi

The polyamine contents of the yeast and mycelial forms of seven dimorphic fungi were examined to determine if a relationship existed between polyamine composition and fungal morphology. Although the polyamine contents differed, no consistent patterns emerged. Evidently, the observed differences in polyamine composition were not related to fungal dimorphism but rather to the growth conditions used to achieve those morphological forms.     

Polyamines in barley seedlings

Polyamine levels in barley seedlings grown in the dark or in diurnal illumination have been determined, by direct dansylation, 3, 6 and 12 days after g     

Polyamines in encephalomyocarditis virus.

Encephalomyocarditis virus contains approximately 200 molecules of putrescine, 100 molecules of spermidine, and 40 molecules of spermine which could neutralize 11% of the viral genome. The same polyamines are present in different proportions in the Krebs ascites tumor cell in which the virus was grown.     

Polyamines in the photosynthetic apparatus

The three main polyamines putrescine (Put), spermidine (Spd) and spermine (Spm) were characterized by HPLC in intact spinach leaf cells, intact chloroplasts, thylakoid membranes, Photosystem II membranes, the light-harvesting complex and the PS II complex. All contain the three polyamines in various ratios; the HPLC polyamine profiles of highly resolved PS II species (a Photosystem II core and the rection center) suggest an enrichment in the polyamine Spm.Abbreviations Chl chlorophyll - HPLC high performance liquid chromatography - LHC light-harvesting complex - PS II Photosystem II - PS II-RC Photosystem II reaction center - Put putrescine - Spd spermidine - Spm spermine - 10%S-core D₁-D₂-Cyt b559-47 kD-43 kD complex     

Polyamines in murine splenic lymphocytes

Diacetyldiamines cause compromised B-lymphocyte function, as evidenced by our previous demonstration of inhibition of mitogen activation and decreased secretion of immunoglobulin in murine spleen cultures. In this study, we report that putrescine and spermidine are differentially metabolized by the cell. Diacetyldiamine, which is also taken up by these cells and metabolized, causes a striking decrease in cell uptake of exogenous putrescine and spermidine. We also report for the first time that several distinct macromolecules containing radioactive polyamines may be resolved, and that hypusine is present in more than one species of macromolecule.     

Polyamines and apoptosis

The natural polyamines putrescine, spermidine and spermine are in multiple ways involved in cell growth and the maintenance of cell viability. In the course of the last 15 years more and more evidence hinted also at roles in gene regulation. It is therefore not surprising that the polyamines are involved in events inherent to genetically programmed cell death. Following inhibition of ornithine decarboxylase, a key step in polyamine biosynthesis, numerous links have been identified between the polyamines and apoptotic pathways. Examples of activation and prevention of apoptosis due to polyamine depletion are known for several cell lines. Elevation of polyamine concentrations may lead to apoptosis or to malignant transformation. These observations are discussed in the present review, together with possible mechanisms of action of the polyamines. Contradictory results and incomplete information blur the picture and complicate interpretation. Since, however, much interest is focussed at present on all aspects of programmed cell death, a considerable progress in the elucidation of polyamine functions in apoptotic signalling pathways is expected, even though enormous difficulties oppose pinpointing specific interactions of the polyamines with pro- and anti-apoptotic factors. Such situation is quite common in polyamine research.     

Light effects in mycorrhizal soybeans

Soybean (Glycine max. L. Merr.) plants were grown in an experiment with a 3 × 3 factorial design using different levels of light (170, 350, and 700 μE·m⁻²·s⁻¹) and P as factors. Plants were grown in a greenhouse in pot cultures using a soil low in plant-available P under three P regimes: no additional P, P added as KH₂PO₄, or P uptake enhanced by colonization of the host plant with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe. Development of the VAM fungal endophyte and of plants under all three P regimes was depressed by limiting light. However, the growth response of VAM plants to increasing light relative to non-VAM plants in the absence of additional P increased while the response relative to non-VAM plants with additional P decreased slightly. The highly significant interaction between the factors (P < 0.001) of the experiment was due to differences in the magnitude and direction of simple effects of the factors. The implications of these differences in terms of source-sink relationships of the symbionts and the value of different non-VAM controls in interpreting VAM effects are discussed.