Polyamines in normal and auxin-induced strawberry fruit development

The possible involvement of polyamines during strawberry ( Fragaria × ananassa Duch.) fruit development was investigated. Putrescine, spermidine, and spermine were identified in strawberry receptacles and achenes at all stages of development. Total (free) polyamine levels decreased from a maximum of 485 nmol g⁻¹ fresh weight at pollination to a minimum of 55 nmol g⁻¹ fresh weight in ripe receptacles. Total polyamine concentrations during corresponding stages of development were consistently higher in achenes than in receptacles, and ranged from 891 to 203 nmol g⁻¹ fresh weight. Removal of achenes from the surface of developing receptacles 10 days after pollination reduced receptacle growth, and re-initiation of growth by application of 1 m M α-naphtaleneacetic acid (α-NAA) was accompanied by a rapid increase in polyamine concentrations 24 h after treatment. Polyamine content per receptacle increased >3-fold in normally developing receptacles and in de-achened, auxin-treated receptacles 10 days after removal of achenes, but did not increase during this period in de-achened receptacles not treated with exogenous auxin. α-NAA increased growth and polyamine levels to a greater extent than the structurally related, but less effective auxin, β-NAA. Polyamine concentrations in receptacles with intact achenes remained similar to those of auxin depleted (de-achened) receptacles, implying that the concentration of these compounds may not be limiting following achene removal.     

The effect of cell turgor on sugar uptake in strawberry fruit cortex tissue

A reduction in cell turgor has been shown to stimulate sugar uptake in several plant sink tissues and it may regulate the import of assimilate into the sink apoplast, as well as maintain cell turgor. To determine whether cell turgor influences sugar uptake by strawberry (Fragaria x ananassa Duch. cv. Brighton) fruit cortex tissue, disks were cut from greenhouse-grown primary fruit at the green-white stage of development and placed in buffered incubation solutions containing either mannitol or ethylene glycol as an osmoticum. Cell turgor of fruit disks was calculated from the difference between the water potential of bathing solution and tissue solute potential after incubation at various osmolarities. Cell turgor increased when tissue disks were placed into mannitol incubation solutions more dilute than the water potential of fresh tissue (about 415 mOsmol kg^?1). The rate of uptake of [¹⁴C]-sucrose or [¹⁴C]-glucose decreased as osmolarity of the incubation solution increased, i.e. as cell turgor declined. Cell turgor and the rate of [¹⁴C]-sucrose uptake were unaffected when rapidly permeating ethylene glycol was used as an osmoticum. A decrease in cell turgor reduced both the V_max of the saturable (carrier mediated) kinetic component of sucrose uptake, and the slope of the linear (diffusional) component. The sulfhydryl binding reagent p-chloromercuibenzenesulfonic acid, an inhibitor of the plasma membrane sucrose carrier, strongly inhibited only the saturable component of sucrose uptake. Increased uptake of the nonmetabolizable sugar, O-methyl-glucose, at high turgor was similar to that of glucose, indicating that carrier activity was influenced by cell turgor, not cell metabolism. Turgor did not influence efflux of [¹⁴C]-sucrose from disks and had no effect on cell viability. Strawberry fruit cells do not possess a sugar uptake system that is stimulated by a reduction in turgor.     

Sugar uptake into strawberry fruit is stimulated by abscisic acid and indoleacetic acid

Changes in sugar uptake into strawberry fruits with maturation and the hormonal effect on uptake mechanisms, though important to fruit development, are not known. Therefore, the kinetics of sugar uptake into strawberry ( Fragaria x ananassa Duch cv. Nyoho) fruit tissue and the effects of abscisic acid (ABA) and indoleacetic acid (LAA) on the mechanism of uptake were investigated at 25 and 35 days after pollination (DAP). Uptake of ¹⁴C-sugar was measured over the concentration range of 2 to 30 m M. Uptake kinetics showed a biphasic response to increasing external concentration of ¹⁴C-sugars, and indicated the presence of P -chlorormercuribenzenesulfonic acid (PCMBS)-sensitive and PCMBS-insensitive uptake. The K_m value for each sugar was in the range of 10 to 20 m M. Stage of development had no effect on K_m. but V_max for glucose decreased with maturation. Further, sucrose was not taken up through a PC-MBS-sensitive transport at 35 DAP. ABA, especially 10 μ M , at 25 DAP stimulated uptake of all sugars, mostly through enhanced PCMBS-insensitive uptake but not PC-MBS-sensitive uptake. In contrast to ABA, stimulation of sugar uptake by IAA was most effective at 1 μ M . The PCMBS-insensitive uptake of each sugar was also stimulated by IAA. Further, the PCMBS-sensitive uptake of glucose was enhanced. The developmental change of PCMBS-sensitive sugar uptake and the effect of ABA and IAA on uptake mechanism in this study are considered to be important in influencing the development and enlargement of fruits.     

Polyamine levels in pollinated and auxin-induced fruit of tomato (Lycopersicon esculentum) during development

The changes taking place during fruit development in the concentration of the 3 polyamine fractions, i.e. free, perchloric acid-soluble conjugates and perchloric acid-insoluble bound polyamines, were analyzed in tomato fruits ( Lycopersicon esculentum Mill, cv. F121) induced to set by either pollination or auxin application. Before the onset of cell division, total polyamines were 50% higher in auxin-treated fruits than in pollinated ones, most of the polyamines being found as perchloric acid-soluble conjugates in both fruit set treatments. At the onset the level of polyamines in both fruit types was 100 times higher than during cell expansion or ripening. The highest polyamine found during cell division was perchloric acid-soluble conjugated spermidine in both fruit set treatments. After cell division, polyamine concentration was similar in both fruit set treatments. The concentration of polyamines in the jelly was similar in pollinated and auxin-induced fruits during cell expansion but not during ripening. At the onset of ripening there was an increase of one order of magnitude in the concentration of perchloric acid-insoluble bound putrescine in the jelly of pollinated fruits. Polyamines were more than 5-fold higher in unpollinated ovaries than in fruits induced to set by either pollination or auxins. It is suggested that pollinated and parthenocarpic fruits differ in their polyamine metabolism during the initial stages of development, but not after cell division. It is also suggested that polyamines undergo rapid turnover during cell division. Perchloric acid-insoluble bound putrescine might play a role in seed formation in tomatoes.     

A morphological study of flower initiation and development in strawberry (Fragaria x ananassa) using cryo-scanning electron microscopy

The morphological changes in the apex of strawberry (Fragaria x ananassa) cv. Elsanta during flower initiation and early development were studied by means of apical dissections and cryo-scanning electron microscopy. Characteristic stages of development were recorded from the earliest discernible evidence of floral initiation until anthesis. The results are discussed in relation to previous studies of floral development in strawberry.     

Effects of sucrose on photosynthesis and phosphoenolpyruvate carboxylase activity of in vitro cultured strawberry plantlets

Photosynthesis and phosphoenolpyruvate carboxylase activity were investigated in 5, 10 and 28 day-old micropropagated strawberry plantlets (Fragaria x ananassa Duch. cv Kent) rooted in vitro with different levels of sucrose (0, 1, 3 and 5%) on cellulose plugs (Sorbarods). The photosynthetic capability was influenced by the level of sucrose in the culture medium with the largest rates of photosynthesis corresponding to the cultures with 0 and 1% sucrose. The apparent quantum yield and the ratio of variable fluorescence to maximum fluorescence were also reduced in plantlets cultured with 3 or 5% sucrose as compared to those with 0 or 1%. Phosphoenolpyruvate carboxylase activity was largest 5 and 10 days after the onset of culture and decreased in the absence of sucrose in the culture medium. At 28 days after the onset of culture, the activity of this carboxylating enzyme was lower than at the beginning of culture and independent of the concentration of sucrose in the culture medium. Phosphoenolpyruvate carboxylase appears to be an important carboxylating enzyme in micropropagated plantlets.     

多胺代谢与癌肿的研究

研究多胺与癌肿的关系。这些癌肿包括Raji癌肿细胞 ,急性淋巴细胞白血病 ,妇产科癌肿 (卵巢癌等 ) ,卵巢癌HO— 891 0细胞 ,肺癌以及胃癌等。研究结果 :(1 )Raji癌细胞株及卵巢癌细胞株 (HO— 891 0 )在培养过程中 ,第 2 4～4 8h多胺水平出现高峰 ,它与这两种癌细胞的核酸合成 ,细胞增殖呈现正相关 ;(2 )急性淋巴细胞白血病患者淋巴细胞及红细胞中多胺水平均升高 ,这有助于对这些病的早期诊断及判断预后 ;(3 )妇科癌症 (尤其卵巢癌 ) ,肺癌 ,胃癌等患者尿液中多胺水平明显高于正常 ,所以尿液中多胺对这些癌肿也是一种有效的诊断标记物     

水稻胚与胚乳分化发育中的内源多胺

稻胚发育过程中,其内源多胺以腐胺、亚精胺为主。在幼胚分化期,腐胺和亚精胺的含量很高;幼胚分化完成时,其含量急剧下降;直至分化后期才趋稳定。在胚及胚乳发育时期,还出现一种未知多胺X_(22),其含量除在胚分化完成时较少外,在胚发育的其他各期中,含量则一直很高。DNA和蛋白质含量的变化,从分化期开始递增直至物质积累成熟期,其趋势均相同。多胺可能参与胚与胚乳中核酸和蛋白质合成的调节。     

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.     

Endogenous polyamines in apple and their relationship to fruit set and fruit growth

The distribution of free and bound polyamines was investigated from blooming until harvest on flower, fruitlets and fruits of Malus domestica Borkh cv. Golden Delicious, Relationships between polyamines and fruit set and growth were also investigated. The level of free polyamines was high only during the first weeks after full bloom and then decreased gradually. The amount of bound trichloroacetic acid-insoluble polyamines was much higher than free polyamines. Bound spermine in particular showed a high value for almost 40 days after full bloom, while spermidine and putrescine were no longer detectable even a few days after full bloom.
In relation to fruit set, it was possible to observe that abscission peaks took place when free polyamine levels were low or decreasing. Insofar as fruit growth is concerned, the most substantial variations in polyamine levels occurred very early in the season when fruit dry weight and protein amount were also changing rapidly and fruit diameter was almost impossible to measure.     

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     

The influence of polyamines on apricot ovary development and fruit set

Polyamine (PA) concentrations of ovaries of two apricot cultivars, ‘S405‐17’ and ‘Bergeron’, collected at three stages of floral development, were analysed. The relationships between PA profiles, ovule development and fruit load between the two apricot cultivars were also determined. We show that PA levels vary with ovary development, depending on the cultivar. Higher concentrations of putrescine (PUT), spermidine and spermine were found in S405‐17 cultivar at all phenological stages. In addition, S405‐17 cultivar had more developed ovules and a higher fruit load than Bergeron. Moreover, the exogenous application of 10 mM PUT in Bergeron increased the percentage of functional ovules from 17.1% (control) to 33.3%. These results prove the effects of PAs on ovary development and indicate the possible improvement of apricot ovule development by their exogenous application. All these results define the relationship between PA content and ovule development in apricot. Further studies would confirm the use of free endogenous PA concentrations as markers of the developmental stage of the ovary, because determination of PA contents is easier and faster than serial sectioning.     

Polyamines and carnation flower senescence: Endogenous levels and the effect of applied polyamines on senescence

The polyamines putrescine and spermine were effective in delaying the senescence of carnation buds, but were ineffective when applied to flowers of which the petals had already opened, and were 90° with respect to the stem. Higher levels of endogenous putrescine were detected in the open flowers than in the buds, and this may explain the negative effect obtained when polyamines were applied to open flowers that were picked for commercial distribution.Abbreviations AOA amino-oxyacetic acid - AVG amino-ethoxyvinyl-glycine - SAM S-adenosyl methionine - STS silver thiosulphate     

Involvement of polyamines in gibberellin-induced development of seedless grape berries

The roles of polyamines (PAs) in the development of seedless grape berries induced by gibberellin (GA₃) was investigated. The development of seedless grape berries was stimulated by the application of putrescine (Put), but not by that of spermidine (Spd) and spermine (Spm), regardless of the presence of GA₃. At harvest, the fresh weight of seedless grape berries treated with 500 ppm Put + 25 ppm GA₃ and 500 ppm Put increased to 111 and 112%, respectively, of the control. Treatment with methylglyoxal-bis (guanyl hydrazone), a potent inhibitor of S-adenosylmethionine decarboxylase that plays a role in Spd and Spm synthesis, did not affect the development of seedless grape berries induced by 100 ppm GA₃. The application of 100 ppm GA₃ significantly increased endogenous free Put levels. Levels of free Spd and Spm were not affected by GA₃. Although the levels of endogenous perchloric acid insoluble bound PAs were higher than those of free PAs, obvious changes in the levels of bound PAs were not observed. These results indicate that free Put is implicated in the development of seedless grape berries induced by GA₃.     

Polyamines and Plant Morphogenesis

Alterations in free and conjugated polyamines (PAs) and the enzymes involved in their biosynthesis, namely arginine decarboxylase, ornithine decarboxylase and S-adenosyl methionine decarboxylase have been reported to occur during cell division, growth, embryogenesis and rhizogenesis in an array of plant materials. However, the relationship, if any, between them and all these processes has not yet been established. It seems that specific PAs at specific concentration ranges are required during critical stages of growth and morphogenetic events. Furthermore, the effects of PA biosynthesis inhibitors vary considerably at different developmental stages of the same tissue. The present review deals with the available information about the possible role of PAs in aforesaid physiological processes.     

Effects of ethylene and auxin on polyamine levels in suspension-cultured tobacco cells

The effects of ethylene and auxin on polyamine levels were studied in suspension-cultured cells of tobacco ( Nicotiana tabacum . L). Treatment of 4-day-cultured cells with ethylene increased the levels of spermidine and spermine. The activities of arginine decarboxylase (ADC; EC 4.1.1.19), ornithine decarboxylase (ODC: EC 4.1.1.17), and S -adenosylmethionine decarboxylase (SAMDC: EC 4.1.1.50) rapidly increased between 3 and 12 h. An auxin, indole-3-acetic acid (IAA), increased polyamine levels and activities of ADC, ODC and SAMDC. The spermine level continued to increase significantly during a 24-h incubation with IAA. The increases in polyamine accumulation induced by ethylene were partially offset by an inhibitor of ethylene action, 2,5-norbornadiene. It is suggested that the auxin-induced polyamine accumulation occurred directly, without metabolic competition between ethylene and polyamine biosynthesis, and indirectly, through auxin-induced ethylene formation.     

Purification and some properties of strawberry mottle virus

Strawberry mottle virus (SMoV) (three isolates: HJ, 3E and N) were transmitted to Chenopodium quinoa plants by sap inoculation. All three isolates induced very similar symptoms consisting of chlorotic spots and ringspots in inoculated leaves, and vein chlorosis, mottling, and dwarfing of the upper leaves. SMoV isolate HJ was purified from infected C. quinoa by homogenisation with 10 mM phosphate buffer, pH 7.2 containing 5% Triton X-100, followed by differential, sucrose density-gradient and CsCl equilibrium density-gradient centrifugations. A fraction with a buoyant density of 1.42g^- cm^-3 after CsCl density-gradient centrifugation was highly infectious to C. quinoa and contained many isometric virus-like particles c. 37 nm in diameter. These virus-like particles were never found in fractions from uninfected preparations. Electrophoretic analysis of a fraction containing virus-like particles revealed that these particles might have a single coat protein subunit with the apparent molecular mass of 26 K daltons and one nucleic acid of 6.6 kilobases. Double-stranded RNA analysis of isolate HJ-infected or uninfected C. quinoa and Fragaria vesca var. semperflorens seedling line ‘Alpine’ plants showed that both infected plants had two infection-specific dsRNA bands of mol. wts 4.5 and 3.9 × 10⁶.     

Polyamines and senescence of maintenance foliage of tea,Camellia sinensis L.

In leaf discs of maintenance foliage of tea (Camellia sinensis) polyamines (PA_s) and kinetin retarded chlorophyll (Chl) loss, whereas inhibitors of PA biosynthesis [difluoromethyl arginine, difluoromethyl ornithine, methylglyoxal-bis(guanylhydrazone)] and abscisic acid (ABA) promoted senescence. The contents of RNA and protein were significantly higher in PA and kinetin treated leaf discs as compared to those treated with inhibitors and ABA. The contents of total and reducing saccharides declined with the progressive loss of Chl, and the concentration of starch increased in all the PA treated leaf discs. Free amino acid content also increased under all the treatments, but the increase was comparatively larger in case of inhibitors application. The authors thank Director, CSIR Complex, Palampur for providing necessary facilities and Merrel Dow Research Institute (Cincinnati, OH) for generous gift of DFMO and DFMA.     

Polyamines: ubiquitous polycations with unique roles in growth and stress responses

Background

Polyamines are small polycationic molecules found ubiquitously in all organisms and function in a wide variety of biological processes. In the past decade, molecular and genetic studies using mutants and transgenic plants with an altered activity of enzymes involved in polyamine biosynthesis have contributed much to a better understanding of the biological functions of polyamines in plants.

Possible roles

Spermidine is essential for survival of Arabidopsis embryos. One of the reasons may lie in the fact that spermidine serves as a substrate for the lysine → hypusine post-translational modification of the eukaryotic translation initiation factor 5A, which is essential in all eukaryotic cells. Spermine is not essential but plays a role in stress responses, probably through the modulation of cation channel activities, and as a source of hydrogen peroxide during pathogen infection. Thermospermine, an isomer of spermine, is involved in stem elongation, possibly by acting on the regulation of upstream open reading frame-mediated translation.

Conclusions

The mechanisms of action of polyamines differ greatly from those of plant hormones. There remain numerous unanswered questions regarding polyamines in plants, such as transport systems and polyamine-responsive genes. Further studies on the action of polyamines will undoubtedly provide a new understanding of plant growth regulation and stress responses.