Ethylene-forming Enzyme Activity Research Articles

Activity of the Ethylene-forming Enzyme in Relation to Plant Cell Structure and Organization

Activity of the ethylene-forming enzyme (EFE) has been compared in leaf discs, isolated cells, protoplasts and vacuoles derived from leaves of pea ( Pisum sativum L.) and bean ( Vicia faba L.).Some 95% of the activity observed with leaf tissue was lost when cells were isolated from the tissue.The limited activity observed with the isolated cells was largely retained by protoplasts and vacuoles isolated from the protoplasts, but was lost when the vacuoles were lysed.Light inhibited EFE activity but did not greatly affect the percentage loss of activity when cells were isolated.Isolation of cells by gentle disruption of cladophylls from Asparagus sprengeri Regel.resulted in a loss of about 80% of EFE activity.It is proposed that full EFE activity requires tissue integrity in addition to a previously noted requirement for cell membrane integrity.

Regulation of Ethylene Biosynthesis in Avocado Fruit during Ripening

Preclimacteric avocado (Persea americana Mill.) fruits produced very little ethylene and had only a trace amount of l-aminocyclopropane-1-carboxylic acid (ACC) and a very low activity of ACC synthase. In contrast, a significant amount of l-(malonylamino)cyclopropane-1-carboxylic acid (MACC) was detected during the preclimacteric stage. In harvested fruits, both ACC synthase activity and the level of ACC increased markedly during the climacteric rise reaching a peak shortly before the climacteric peak. The level of MACC also increased at the climacteric stage. Cycloheximide and cordycepin inhibited the synthesis of ACC synthase in discs excised from preclimacteric fruits. A low but measurable ethylene forming enzyme (EFE) activity was detected during the preclimacteric stage. During ripening, EFE activity increased only at the beginning of the climacteric rise. ACC synthase and EFE activities and the ACC level declined rapidly after the climacteric peak. Application of ACC to attached or detached fruits resulted in increased ethylene production and ripening of the fruits. Exogenous ethylene stimulated EFE activity in intact fruits prior to the increase in ethylene production. The data suggest that conversion of S-adenosylmethionine to ACC is the major factor limiting ethylene production during the preclimacteric stage. ACC synthase is first synthesized during ripening and this leads to the production of ethylene which in turn induces an additional increase in ACC synthase activity. Only when ethylene reaches a certain level does it induce increased EFE activity.

Activity of the Ethylene-forming Enzyme Measured in vivo at Different Cell potentials

Summary Activity of the ethylene-forming enzyme (EFE) has been determined in hypocotyl segments of mung bean ( Vigna radiata L.) and in discs of red beet ( Beta vulgaris L.) at the same time as the plasma membrane potential difference, measured with a microelectrode, has been progressively reduced by titration with the protonophores 2,4-dinitrophenol and carbonyl cyanide m-chloropheny1hydrazone and with KCl. Treatment with the protonophores affected EFE activity in both the mung bean hypocotyls and in the beet discs, although in different ways in the two tissues, while the depolarisation resulting from KCl treatment did not affect the EFE activity of either tissue. The results obtained are not consistent with the proposal of John (1983, FEBS Letters 152, 141) that a potential-dependent EFE activity is located at the plasma membrane of plant cells.

Ethylene and the Growth of Rice Seedlings

Etiolated whole rice seedlings enclosed in sealed vials produced ethylene at a rate of 0.9 picomole per hour per seedling. When 2-centimeter-long shoots were subdivided into 5-millimeter-long sections, the sections containing the tip of the shoot evolved 37% of the total ethylene with the remaining 63% being produced along a gradient decreasing to the base of the shoot. The tip of the coleoptile also had the highest level of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and of the ethylene-forming enzyme activity. Ethylene is one of the factors controlling coleoptile elongation. Decapitation of the seedling reduced ethylene evolution to one-third its original level and inhibited coleoptile growth. In short-term experiments, the growth rate of decapitated seedlings was restored to almost that of intact seedlings by application of ethylene at a concentration of 10 microliters per liter. Apart from ethylene, O(2) also participates in the control of coleoptile growth. When rice seedlings were grown in a gas mixture of N(2) and O(2), the length of the coleoptiles reached a maximum at a concentration of 2.5% O(2). Lower and higher concentrations of O(2) reduced coleoptile growth. The effect of exogenous ethylene on coleoptile growth was also O(2) dependent.

Effect of temperature on ethylene biosynthesis in carnation petals

Carnation petals, at a stage in which they are already producing ethylene, show a sigmoidal dependency of ethylene production on temperature within the range of 0 to 30°C. An Arrhenius plot of these data show a break atca. 22°C in the straight lines connecting the points. The activity of the ethylene-forming enzyme (EFE), measured bothin vitro, using isolated membranes, andin vivo, using petals pretreated with 1-aminocyclopropane-1-carboxylic acid (ACC), shows an exponential dependency on temperature within the same range. Arrhenius plots of EFE activity fail to show any discontinuity. In contrast, ACC synthase activity measuredin vitro shows the same sigmoidal dependency on temperature as that of the intact petals. We suggest, therefore, that ACC synthase activity is the rate-limiting step mediating the influence of temperature on ethylene biosynthesis by carnation petals over the range studied.

Relationship between the activity of the ethylene-forming enzyme and the level of intracellular 2,4-dichlorophenoxyacetic acid in pear cell culturesin vitro

Ethylene production by auxin-dependent pear cells culturedin vitro falls rapidly when they are deprived of 2,4-D. This phenomenon is associated with a decrease in ACC production. Readdition of 2,4-D causes a resumption of ACC production and ethylene synthesis. Ethylene-forming enzyme (EFE) activity, although never limiting, decreases sharply during 2,4-D depletion and rises again upon addition of 2,4-D. This increase in the EFE activity is not a rapid response to 2,4-D, since it requires several hours. Changes in EFE activity follow the same pattern as changes in 2,4-D concentration; the decrease in EFE activity is also concomitant with a decrease in the ability of 2,4-dinitrophenol to inhibit ethylene production. The possible role of auxins in the modulation of EFE activity is discussed.

トマトとキュウリ果実の生育•成熟に伴う1-アミノシクロプロパン-1-カルボン酸 (ACC) 含量とエチレン生成酵素活性の変化

トマトとキュウリ果実の生育•成熟に伴う1-アミノシクロプロパン-1-カルボン酸 (ACC) 含量とエチレン生成酵素活性の変化

キウイ果実のエチレン生成

Kiwifruits (Actinidia chinensis Planch. cv. Hayward) produced ethylene at an increasing rate at 21°C after exceeding a threshold level of 0.1μlkg-1h-1. There was a wide variation in time before the burst of ethylene production by individual fruits was evident after transferred from 1°C to 21°C. This variation became less and the time necessary for individual fruits to reach the increased level of ethylene became shorter and uniform as the storage period at a low temperature (1°C) extended. The increased rate of ethylene production was paralleled by the increased internal ethylene concentration and accompanied by the rise in respiration and soluble solids content and flesh softening. 1-Aminocyclopropane-1-carboxylic acid (ACC) content in the fruit tissue increased in parallel with the rise in the rate of ethylene production. ACC synthase activity also increased in the ethylene forming tissue. Ethylene forming enzyme (EFE) activity increased with the increase in the rate of ethylene production by the fruit. Ethylene production by the fruit tissue was strongly inhibited by aminoethoxyvinylglycine (AVG). EFE activity in the tissue was strongly inhibited by Co2+, n-propyl gallate (PG) and sodium caprylate (CAP). These results may indicate that ethylene biosynthesis in the kiwifruit proceeds along the methionine and ACC pathway.

Nonosmotic Inhibition by Sugars of the Ethylene-Forming Activity Associated with Microsomal Membranes from Carnation Petals

The activity of the membrane-bound ethylene-forming enzyme, previously reported in carnation (Dianthus caryophyllus L. cv White Sim) petals (Mayak, Legge, Thompson 1981 Planta 153: 49-55), is inhibited by sugars. Of the various sugars tested, sorbitol was the most effective and glucose the least. The effect of sugars was also evaluated on solubilized ethylene-forming enzyme activity, obtained by the use of 0.6% Nonidet NP-40 detergent. Similar to the membrane-bound activity, the solubilized activity was also inhibited. Kinetic studies revealed that the inhibition by sugars is reversible, and that inhibition by sucrose is uncompetitive while that by sorbitol is competitive. During senescence of petals, a decline in sugar content and climacteric like increase in ethylene occurs. Hence, the physiological relevance of sugar inhibition and its possible involvement in the regulation of ethylene biosynthesis is suggested.

The effect of plant-hormone pretreatments on ethylene production and synthesis of 1-aminocyclopropane-1-carboxylic acid in water-stressed wheat leaves

Excised wheat (Triticum aestivum L.) leaves, when subjected to drought stress, increased ethylene production as a result of an increased synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC) and an increased activity of the ethyleneforming enzyme (EFE), which catalyzes the conversion of ACC to ethylene. The rise in EFE activity was maximal within 2 h after the stress period, while rehydration to relieve water stress reduced EFE activity within 3 h to levels similar to those in nonstressed tissue. Pretreatment of the leaves with benzyladenine or indole-3-acetic acid prior to water stress caused further increase in ethylene production and in endogenous ACC level. Conversely, pretreatment of wheat leaves with abscisic acid reduced ethylene production to levels produced by nonstressed leaves; this reduction in ethylene production was accompanied by a decrease in ACC content. However, none of these hormone pretreatments significantly affected the EFE level in stressed or nonstressed leaves. These data indicate that the plant hormones participate in regulation of water-stress ethylene production primarily by modulating the level of ACC.