Calcium in plant senescence and fruit ripening

Abstract. Calcium has long been associated with regulation of the ripening process of fruit and post-harvest storage life. Specifically, maintenance of relatively high calcium concentrations in fruit tissue results in a slower rate of ripening, as seen in lower respiration rates, reduced ethylene production, and slower softening of fruit flesh. There are also some specific fruit disorders such as bitter pit, which can be prevented if sufficient calcium is present. Senescence of other plant tissues such as leaves and flowers has also been shown to be retarded by the application of calcium.
Work leading to the above information is reviewed and discussed in the context of what is currently known of cellular regulation of calcium in plants. The major sites for the action of calcium in senescence and ripening are suggested to be in membrane structure and function, and in cell wall structure. Although high external concentrations of calcium are an advantage in reducing the rate of senescence or ripening, it is emphasized that normal cell function requires the maintenance of low concentrations of free calcium in the cell cytosol. It is suggested that one possible feature of senescence is a breakdown in such cellular regulation.     

月季切花衰老过程中多胺与乙烯的关系

月季切花瓶插过程中,内源腐胺在前2天略有增加,内源亚精胺、精胺、多胺总量则呈下降趋势,乙烯释放速率在第3天达到最高峰;多胺抑制剂甲基乙醛-双咪腙处理抑制了亚精胺、精胺的合成,增加了乙烯的释放速率;乙烯抑制剂氨氧乙酸处理推迟腐胺高峰的到来,降低了乙烯的释放速率,而且在瓶插期的前2天内源亚精胺、精胺含量较高。结果表明,具乙烯跃变型特征的月季切花衰老过程中,多胺与乙烯在其生物合成过程中相互竞争S-腺苷甲硫氨酸作为其合成的前体。     

Identification of cDNA clones for tomato (Lycopersicon esculentum Mill.) mRNAs that accumulate during fruit ripening and leaf senescence in response to ethylene

Changes in gene expression during foliar senescence and fruit ripening in tomato (Lycopersicon esculentum Mill.) were examined using in-vitro translation of isolated RNA and hybridization against cDNA clones.During the period of chlorophyll loss in leaves, changes occurred in mRNA in-vitro translation products, with some being reduced in prevalence, whilst others increased. Some of the translation products which changed in abundance had similar molecular weights to those known to increase during tomato fruit ripening. By testing RNA from senescing leaves against a tomato fruit ripening-related cDNA library, seven cDNA clones were identified for mRNAs whose prevalence increased during both ripening and leaf senescence. Using dot hybridization, the pattern of expression of the mRNAs corresponding to the seven clones was examined. Maximal expression of the majority of the mRNAs coincided with the time of greatest ethylene production, in both leaves and fruit. Treatment of mature green leaves or unripe fruit with the ethylene antagonist silver thiosulphate prevented the onset of senescence or ripening, and the expression of five of the seven ripening- and senescence-related genes.The results indicate that senescence and ripening in tomato involve the expression of related genes, and that ethylene may be an important factor in controlling their expression.Abbreviations cDNA copy-DNA - MW molecular weight - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulphate     

The effect of polyamines on ethylene synthesis during normal and pollination-induced senescence of Petunia hybrida L. flowers

Senescence of Petunia hybrida L. flowers is accompanied by a climacteric pattern in ethylene production and a rapid decline in the levels of putrescine and spermidine during the preclimacteric phase. The decrease in spermidine is caused by the decline in the availability of putrescine which is initially synthesized from L-arginine via agmatine and N-carbamoylputrescine. Inhibition of putrescine and polyamine synthesis resulted in a rapid drop in the levels of putrescine and spermidine without resulting in a concomitant increase in ethylene production. These results indicate that polyamine synthesis is not involved in the control of ethylene synthesis through its effect on the availability of S-adenosylmethionine, and is confirmed by the results obtained with pollinated flowers. Treatment with polyamines may stimulate or suppress ethylene production in the corolla, depending on the concentrations applied. In unpollinated flowers the onset of the climacteric rise in ethylene production was accelerated after treatment with polyamines. However, in pollinated flowers this process was delayed as a result of treatment with low concentrations of polyamines. The effects of exogenous polyamines on ethylene production in both pollinated and unpollinated flowers indicate that ethylene synthesis in these flowers is not regulated by a feedback control mechanism. Although polyamines do not play a key role in the control of ethylene production during the early stages of senescence through their effect on the availability of S-adenosylmethionine, it appears that they play an important role in some of the other processes involved in senescence.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - MGBG methylglyoxal bis-(guanylhydrazone) - SAM S-adenosylmethionine     

An increase in ethylene sensitivity following pollination is the initial event triggering an increase in ethylene production and enhanced senescence of Phalaenopsis orchid flowers

Cut Phalaenopsis (Phalaenopsis hybrid, cv. Herbert Hager) flowers usually last about 2 weeks. Following pollination however, there is a rapid acceleration of the wilting process, which is completed within 2 days. The first event detected following pollination was an increase in ethylene sensitivity. This increased sensitivity began about 4 h after pollination and peaked 6 h later. A subsequent increase in ethylene production could only be detected 12 to 14 h after pollination. Treatment of the flowers with silver thiosulfate or 1-methylcyclopropene, both inhibitors of ethylene action, completely inhibited the pollination-induced increase in ethylene production and the enhanced senescence of the flowers. This indicates that the pollination-induced increase in ethylene production is a response to the existing ethylene. Treatment of flowers with calcium and its ionophore A23187, which increased ethylene sensitivity and protein phosphorylation, also promoted ethylene production and senescence of unpollinated flowers, EGTA, a calcium chelator, decreased the sensitivity of pollinated flowers to ethylene and delayed and decreased the pollination-induced increase in ethylene production. We suggest that the pollination-induced increase in ethylene sensitivity is the initial pollination-induced event triggering the enhancement of ethylene production, which leads to enhanced senescence of Phalaenopsis flowers.     

Changes in polar lipids during ripening and senescence of cherry tomato (Lycopersicon esculentum): Relation to climacteric and ethylene increases

The entire senescence period, including ripening, is characterized in cherry tomato ( Lycopersicon esculentum Mill. var. cerasiforme Alef.) by two successive changes in overall polar lipid content. The rise in respiration of the fruit in the climacteric phase is accompanied by a large increase in lipids, notably phospholipids, such as phosphatidylcholine and phosphatidic acid. This suggests the coexistence of anabolic and catabolic processes in this first period. At the degreening stage of the fruit, decreased levels of monogalactosyldiacylglycerol and the disappearance of trigalactosyldiacylglycerol may indicate some degradation of the chloroplast compartment. Following a respiratory upsurge, a sudden breakdown of total lipids occurs concomitantly with maximal ethylene production. This breakdown is essentially caused by a parallel decrease in the amounts of phosphatidylcholine, phosphatidylethanolamine, phosphatidic acid and also phosphatidylglycerol. However, in the cherry tomato, lipid peroxidation, evaluated by alteration of fatty acid distribution, seems insufficient to account for the ethylene peak.     

Role of ethylene action in ethylene production and poststorage leaf senescence and survival of pelargonium cuttings

This study investigated the role of ethylene action in ethylene production and in poststorage performance of pelargonium cuttings. Cuttings of zonal pelargonium (Pelargonium x hortorum L.H. Bailey) of the cultivars Isabell and Mitzou were treated with ethylene and with the ethylene action inhibitors 1-methylcyclopropene (MCP), silver-thiosulfate (STS) and silver nitrate (SN) and were stored in the dark at different temperatures (5, 12, and 20 °C) for 48 h. Ethylene concentrations in the storage boxes were monitored and poststorage leaf senescence, survival and root formation of cuttings were determined. Applications of MCP resulted in a significant increase of ethylene evolution by cuttings of both cultivars which was more pronounced with increasing storage temperature. After 48 h of storage at 20 °C, ethylene concentrations were more than 20-fold higher for the MCP-treated cuttings as compared to those of the untreated controls. Also preharvest applications of STS and SN increased ethylene evolution by cuttings, even though these effects were less pronounced. However, application of these inhibitors caused severe poststorage leaf injury. Application of ethylene during storage had no effect on subsequent leaf damage. Leaf senescence during rooting and decay of cuttings, which raised with increasing storage temperature, could only partially been reduced by MCP. The results strongly support the conclusion, that in zonal pelargonium cuttings, ethylene production is controlled by autoinhibition, and clearly indicate, that temperature dependent processes other than ethylene action are substantially involved in storage-induced leaf senescence and decay.     

Programme of senescence in petals and carpels of Pisum sativum L. flowers and its control by ethylene

The role of ethylene in the control of senescence of both petals and unpollinated carpels of pea was investigated. An increase in ethylene production accompanied senescence, and the inhibitors of ethylene action were effective in delaying senescence symptoms in different flower verticils. Pollination did not seem to trigger the senescence syndrome in the corolla as deduced from the observation that petals from pollinated and unpollinated flowers and from flowers whose carpels had been removed senesced at the same time. A cDNA clone encoding a putative ethylene-response sensor (psERS) was isolated from pea flowers, and the pattern of expression of its mRNA was studied during development and senescence of different flower tissues. The levels of psERS mRNA paralleled ethylene production (and also levels of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) mRNA) in both petals and styles. Silver thiosulfate treatments were efficient at preventing ACO and psERS mRNA induction in petals. However, the same inhibitor showed no ability to modify expression patterns in pea carpels around the anthesis stage, suggesting different controls for ethylene synthesis and sensitivity in different flower organs. Received: 18 June 1998 / Accepted: 22 December 1998     

Role of ethylene in senescence of watercress leaves

Detached watercress leaves showed a rapid senescence rate as compared with other herbs. It was therefore of interest to investigate the role of ethylene in the rapid senescence of watercress leaves, and So estimate the efficacy of various inhibitors of elhylene synthesis (aminoethoxyvinylglycine, AVG) and action (CO₂, Ag⁺) in retarding senescence processes. The progress of senescence in watercress bunches (leaves attached to cut stems) and in detached leaves was estimated by measuring the rate of chlorophyll (Chl) loss, proteolysis and lipid oxidation. Evidence is presented showing that application of 11% CO₂ to watercress bunches in a flow-through system had a long-lasting effect on senescence, exhibited by highly efficient retardation of all the senescence processes tested. On the other hand, application of AVG (O.1 m M ) or Ag-(30 μ M ) to detached leaves affected Chl loss much more than prciteolysis. These results suggest that the senescence-retarding activity of CO₂ cannot be attributed solely to its action as an anli-ethylene agent and that not all senescence-associated processes are regulated by ethylene.     

采后荔枝果实冷害过程中多胺含量的变化

以桂味荔枝果实为材料,研究冷害及外源亚精胺(Spd)处理对果实膜透性和内源多胺含量变化的影响。结果表明,在0℃下贮藏时果实发生冷害过程中,荔枝果皮中腐胺(Put)、Spd、精胺(Spm)含量在14d后明显增加,膜透性快速增大,21d时果皮出现明显的冷害褐变,Put进一步积累,而Spm含量下降,Spd保持较高水平。非冷害温度(3℃)下贮藏时,果皮多胺含量变化相对较小。0℃下果肉的多胺含量和变化幅度低于3℃果实,并延迟7d衰老。外源Spd处理明显提高果实内源多胺含量的同时,延缓了果皮相对膜透性增加,减轻了冷害。这表明果皮中Put的积累可能是荔枝果实冷害的结果,冷藏初期Spm含量的上升可能是果实对冷害的防卫反应。     

New volatile and water-soluble ethylene antagonists

Twenty cyclopropenes were prepared and their anti-ethylene activity was evaluated in the fruit ripening and plant senescence bioassays. The treatment of banana fruits with developed antagonists led to delay of fruit ripening. Some antagonists were capable to extend exhibition life of cut mini carnation flowers as well as delay senescence of bean leaves. The potency of ethylene antagonists declined with increase in molecular weight and reduction in their solubility in water, irrespective of bioassay used. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 4, pp. 585–591. The text was submitted by the author in English.     

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     

Effect of polyamines on ethylene production

The polyamines putrescine, cadaverine, spermidine and spermine reduced the amount of ethylene produced by senescing petals of Tradescantia but they did not prevent anthocyanin leakage from these same petals. These polyamines also inhibited auxin-mediated ethylene production by etiolated soybean hypocotyls to less than 7 % of the control. The basic amino acids lysine and histidine reduced the amount of auxin-induced ethylene produced by soybean hypocotyls by ca 50 %. In the hypocotyls, methionine was unable to overcome the inhibition caused by the polyamines. The polyamines spermidine and spermine inhibited ethylene production induced by the application of 1-aminocyclopropane-1-carboxylic acid and they also reduced the endogenous content of this amino acid in the treated tissues.     

Melatonin: A master regulator of plant development and stress responses

Melatonin is a pleiotropic molecule with multiple functions in plants. Since the discovery of melatonin in plants, numerous studies have provided insight into the biosynthesis, catabolism, and physiological and biochemical functions of this important molecule. Here, we describe the biosynthesis of melatonin from tryptophan, as well as its various degradation pathways in plants. The identification of a putative melatonin receptor in plants has led to the hypothesis that melatonin is a hormone involved in regulating plant growth,aerial organ development, root morphology, and the floral transition. The universal antioxidant activity of melatonin and its role in preserving chlorophyll might explain its anti-senescence capacity in aging leaves. An impressive amount of research has focused on the role of melatonin in modulating postharvest fruit ripening by regulating the expression of ethylene-related genes.Recent evidence also indicated that melatonin functions in the plant's response to biotic stress,cooperating with other phytohormones and wellknown molecules such as reactive oxygen species and nitric oxide. Finally, great progress has been made towards understanding how melatonin alleviates the effects of various abiotic stresses, including salt, drought, extreme temperature, and heavy metal stress. Given its diverse roles, we propose that melatonin is a master regulator in plants.     

Inhibition of ethylene-induced cellular senescence symptoms by 1-methylcyclopropene, a new inhibitor of ethylene action

Ethylene is known to accelerate flower senescence, but the sequence of events that links its interaction with the tissue and the final senescence symptoms is still obscure. Recently, 1-methylcyclopropene (1-MCP) was found to inhibit ethylene-induced wilting in flowers. This work was carried out in order to investigate the effects of 1-MCP on cellular senescence symptoms in petunia flowers following expossure to ethylene. Cut petunia ( Petunia hybrida ) flowers that were exposed to ethylene for 12 h at concentrations of 1–12 ppm wilted sooner than their untreated counterparts. This effect was abolished by a 6-h pre-treatment with 1-MCP. Immediately following the ethylene treatment, decreases in petal fresh weight and total protein content were measured, along with higher electrolyte leakage, and lower membrane lipid fluidity and protein content. When applied alone, 1-MCP had relatively little impact on these parameters. However, when the flowers were treated with 1-MCP prior to the ethylene treatment, ethylene had no effect. These results indicate that while ethylenes effects on wilting were obvious 3 days after the treatment, cellular parameters were affected already at the end of the treatment. Since 1-MCP repressed these early ethylene effects, it was concluded that it interferes with ethylene action in petunia flowers at a rather early stage, long before apparent wilting.     

Internal carbon dioxide and ethylene levels in ripening tomato fruit attached to or detached from the plant

The carbon dioxide and ethylene concentrations in tomato fruit ( Lycopersicon esculentum cv. Castelmart) and their stage of ripeness (characteristic external color changes) were periodically measured in fruit attached to and detached from the plant. An external collection apparatus was attached to the surface of individual tomato fruit to permit non-destructive sampling of internal gases. The concentration of carbon dioxide and ethylene in the collection apparatus reached 95% of the concentration in the fruit after 8 h. Gas samples were collected every 24 h. A characteristic climacteric surge in carbon dioxide (2-fold) and ethylene (10-fold) concentration occurred coincident with ripening of detached tomato fruit. Fruit attached to the plant exhibited a climacteric rise in ethylene (20-fold) concentration during ripening, but only a linear increase in carbon dioxide concentration. The carbon dioxide concentration increases in attached fruit during ripening, but the increase is a continuation of the linear increase seen in both attached and detached fruit before ripening and does not exhibit the characteristic pattern normally associated with ripening climacteric fruit. In tomato fruit, it appears that a respiratory climacteric per se, which has been considered intrinsic to the ripening of certain fruit, may not be necessary for the ripening of "climacteric" fruit at all, but instead may be an artifact of using harvested fruit.     

多效唑对花生叶片多胺含量及衰老的调节作用

通过对大田条件下生殖生长期花生喷施不同浓度的多效唑,研究了多效唑对叶片内源多受及其它衰老指标的影响,结果证明多效唑对内源多胺的影响较复杂,多效唑降低了幼嫩叶片的多胺含量,却提高了成熟叶片衰老阶段的多胺含量,并起到延缓衰老的作用,讨论了多效唑影响多胺含量的可能原因。     

The Roles of Phytohormones in Development as Studied in Transgenic Plants

The study of transgenic plants has greatly advanced our understanding of the control of development and metabolism. The ability to isolate and modify genes greatly extends the range of what is technically feasible. In the area of hormone biology, transgenic plants have helped to elucidate the pathways of synthesis, the metabolic control points, and the biological functions of the various phytohormones. This review covers the available genes that modulate the metabolism and perception of the phytohormones. One of the most significant conclusions coming out of transgenic plant work is the complex interaction among the different classes of phytohormones. For example, increasing the level of the auxin indole-3-acetic acid (IAA) in a plant has the secondary effect of inducing ethylene biosynthesis. This complication can be circumvented by combining transgenic plants modulating multiple hormones or through the use of available mutants. In this manner, transgenic plants have been utilized to unambiguously define the roles of auxin, cytokinin, and ethylene in the control of apical dominance. The power of transgenic plants as tools in hormone biology is perhaps best illustrated by work on ethylene. In this case, the modular characterization of genes led to elucidation of the biosynthetic pathway. Availability of the biosynthetic genes has permitted detailed analysis of the regulation of synthesis, definition of the role of ethylene in the control of several developmental processes, and the application of that knowledge for agricultural improvement.