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1.
To investigate the relationship between methyl jasmonate (MeJA) and ethylene in leaf senescence, we studied the effects of
MeJA on ethylene production and ethylene biosynthetic enzyme activities in oat (Avena sativa L.) leaf segments incubated in darkness. MeJA promoted dark-induced senescence judged from the contents of chlorophyll and
protein, and increased ethylene production 6 times of the control. MeJA also increased the activities of ethylene biosynthetic
enzymes, 1-aminocyclopropane carboxylic acid (ACC) synthase and ACC oxidase as compared to control. In MeJA-treated leaf segments,
ACC synthase activity reached its maximum level at 24 h of incubation and ACC oxidase activity peaked at 6 h of incubation.
Aminoethoxyvinylglycine (AVG) and Co 2+, inhibitors of ACC synthase and ACC oxidase respectively, reduced MeJA-induced ethylene production. They also delayed leaf
senescence that was promoted by the treatment of MeJA. From these results, we can suggest that MeJA increased the activities
of ACC synthase and ACC oxidase, these increased activities lead to increase in ethylene production and this increased ethylene
production might promote dark-induced leaf senescence. 相似文献
2.
Ethylene biosynthesis in leaf discs of tobacco ( Nicotiana tabacum L. cv. Xanthi), as measured by the conversion of L-[3,4- 14C]-methionine to 14C 2H 4, was markedly inhibited by exogenous ethylene. This inhibition was accompanied by a decrease in total (free + conjugated) content of 1-aminocyclopropane-1-carboxylic acid (ACC), most of which appeared in its conjugated inactive form. The autoinhibitory effect of ethylene was reversible and could be relieved by Ag +. The Ag +-treated leaf discs, with or without ethylene, contained only free ACC at an increased level. The results suggest that in tobacco leaves, the autoinhibition of ethylene production resulted from reduction in the availability of free ACC, through both suppression of ACC formation and increased ACC conjugation. 相似文献
3.
Wounding delays the loss of chlorophyll (Chl) that normally occurs when oat ( Avena sativa L.) leaf segments are held in the dark. There was a continued increase in ethylene production during the senescence of the control segments; in contrast, ethylene production by the wounded segments, although it increased by a factor of 2–3 times, reached its peak in 48 h and then dropped sharply to below the basal level. Added 1-aminocyclopropane-1-carboxylic acid (ACC) caused a very large increase in ethylene production in both control and wounded segments, but it increased the rate of Chl loss, though only marginally. Aminoethoxyvinylglycine (AVG) inhibited ethylene production by both control and wounded segments and this did decrease the Chl loss, but only in the control segments. In the wounded segments, AVG antagonized the Chl-retaining action of the wound. Since wounding delayed the loss of Chl and yet caused a moderate increase in ethylene production, we conclude that the ethylene production by senescing oat leaves is not the main controlling influence in the wounding effect. The data also throw doubt on the causal participation of ethylene in normal Chl loss by these leaves in darkness. 相似文献
4.
The role of ethylene in the senescence of detached rice leaves in relation to their changes in 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production was studied. In freshly excised rice leaf segments, ACC level and ethylene production rates were very low. Following incubation, the rates of ethylene production increased and reached a maximum in 12 h, and subsequently declined. The rise of ethylene production was associated with a 20- to 30-fold increase in ACC level. Ethylene seems to be involved in the regulation of the senescence of detached rice leaves. This conclusion was based on the observations that (a) maximum ethylene production preceded chlorophyll degradation, (b) ACC application promoted chlorophyll degradation, (c) inhibitors of ethylene production and ethylene action retarded chlorophyll degradation, and (d) various treatments such as light, cycloheximide, α,α-dipyridyl, Ni2+, and cold temperature, which retarded chlorophyll degradation, also inhibited ethylene production. Abscisic acid promoted senescence but significantly decreased ethylene production, whereas benzyladenine retarded senescence but promoted ethylene production. This is interpreted to indicate that abscisic acid treatment increased the tissue sensitivity to ethylene, whereas benzyladenine treatment decreased it. 相似文献
5.
The mechanism of light-inhibited ethylene production in excised rice ( Oryza sativa L.) and tobacco ( Nicotiana tabacum L.) leaves was examined. In segments of rice leaves light substantially inhibited the endogenous ethylene production, but when CO 2 was added into the incubation flask, the rate of endogenous ethylene production in the light increased markedly, to a level which was even higher than that produced in the dark. Carbon dioxide, however, had no appreciable effect of leaf segments incubated in the dark. The endogenous level of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, was not significantly affected by lightdark or CO 2 treatment, indicating that dark treatment or CO 2exerted its effect by promoting the conversion of ACC to ethylene. This conclusion was supported by the observations that the rate of conversion of exogenously applied ACC to ethylene was similarly inhibited by light, and this inhibition was relieved in the presence of CO 2. Similar results were obtained with tobacco leaf discs. The concentrations of CO 2 giving half-maximal activity was about 0.06%, which was only slightly above the ambient level of 0.03%. The modulation of ACC conversion to ethylene by CO 2 or light in detached leaves of both rice and tobacco was rapid and fully reversible, indicating that CO 2 regulates the activity, but not the synthesis, of the enzyme converting ACC to ethylene. Our results indicate that light inhibition of ethylene production in detached leaves is mediated through the internal level of CO 2, which directly modulates the activity of the enzyme converting ACC to ethylene.Abbreviation ACC
1-aminocyclopropane-1-carboxylic acid
Recipient of a Republic of China National Science Council Fellowship 相似文献
6.
A model is presented of the regulation of ethylene biosynthesis in relation to submergence and flooding resistance. It is based on time-course measurements of ethylene production, ethylene accumulation, and concentrations of free and conjugated 1-aminocyclo-propane-1-carboxylic acid (ACC) in submerged and drained flooding-resistant Rumex palustris Sm. and flooding-sensitive Rumex acetosella L. plants. From these data, in vivo reaction rates of the final steps in the ethylene biosynthetic pathway were calculated. According to our model, submergence stimulates ACC formation and inhibits conversion of ACC to ethylene in both Rumex species, and as a result, ACC accumulates. This may explain the stimulated ACC conjugation observed in submerged plants. Although submergence inhibited ethylene production, physical entrapment increased endogenous ethylene concentrations in both flooding-resistant R. palustris and flooding-sensitive R. acetosella plants. However, R. palustris plants controlled their internal ethylene levels in the long term by a negative regulation of ACC synthase induced by ethylene. In flooding-sensitive R. acetosella plants, absence of negative regulation increased internal ethylene levels to more than 20 [mu]L L-1 after 6 d of submergence. This may accelerate the process of senescence and contribute to their low level of flooding resistance. 相似文献
7.
The regulatory role of ethylene in leaf senescence was studied with excised tobacco leaf discs which were allowed to senesce in darkness. Exogenous ethylene, applied during the first 24 hours of senescence, enhanced chlorophyll loss without accelerating the climacteric-like pattern of rise in both ethylene and CO 2, which occurred in the advanced stage of leaf senescence. Rates of both ethylene and CO 2 evolution increased in the ethylene-treated leaf discs, especially during the first 3 days of senescence. The rhizobitoxine analog, aminoethoxy vinyl glycine, markedly inhibited ethylene production and reduced respiration and chlorophyll loss. Pretreatment of leaf discs with Ag + or enrichment of the atmosphere with 5 to 10% CO 2 reduced chlorophyll loss, reduced rate of respiration, and delayed the climacteric-like rise in both ethylene and respiration. Ag + was much more effective than CO 2 in retarding leaf senescence. Despite their senescence-retarding effect, Ag + and CO 2, which are known to block ethylene action, stimulated ethylene production by the leaf discs during the first 3 days of the senescing period; Ag + was more effective than CO 2. The results suggest that although ethylene production decreases prior to the climacteric-like rise during the later stages of senescence, endogenous ethylene plays a considerable role throughout the senescence process, presumably by interacting with other hormones participating in leaf senescence. 相似文献
8.
Hormonal metabolism associated with fruit development in muskmelon was investigated by measuring IAA, ABA, and ACC levels in several tissues at various stages of development. In addition, levels of conjugated IAA and ABA were determined in the same tissues. Ethylene production, which is believed to signal the ripening and senescence of mature fruit, was also measured. Ethylene production was highest in the outer tissue near the rind and gradually declined during maturation, except for a dramatic increase in all fruit tissues at the climacteric. In contrast to ethylene production, ACC levels increased during maturation and remained equal throughout the fruit until the climacteric, when levels in the outer tissues increased nearly 5-fold over levels in the inner tissues. The consistent presence of ACC indicates that ACC oxidase rather than the availability of ACC regulates ethylene production in developing fruits. ABA and ABA esters generally declined during maturation, however an increase in ABA esters associated with the outer mesocarp tissue was observed in fully mature, climacteric fruit. IAA and IAA conjugates were only found in the outer tissue near the rind, and their levels remained low until the fruit was fully mature and entering the climacteric. At that time, increased levels of conjugates were detected. The late burst of hormonal metabolism in the outer mesocarp tissue appeared to signal its degeneration and the deterioration that typically occurs in ripening fruit. The tissue-specific conjugation of IAA and ABA, in addition to the production of climacteric ethylene, may represent part of the signaling mechanism initiating ripening and eventual deterioration of tissues in muskmelon fruits.Abbreviations ABA
abscisic acid
- ACC
1-aminocylopropane-1-carboxylic acid
- DAP
days after pollination
- IAA
indole-3-acetic acid 相似文献
9.
Light inhibits while carbon dioxide enhances the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene in oat ( Avena sativa L. cv. Victory) leaf segments. The possibility that the light inhibition is mediated through changes of carbon dioxide has been investigated. The level of CO 2 increases or decreases in the sealed incubation vial in darkness or in light, respectively, which can apparently account for the differences in ACC-dependent ethylene production between the dark and light treatments. However, although the evolution of ethylene from ACC in the dark is reduced upon depletion of CO 2, the difference between light and dark is still very noticeable. Moreover, the production of the ethylene in CO 2-free air in the dark was still higher than in the light, where the concentration of CO 2 was 0.01%. It is proposed that the light effect on the conversion of ACC to ethylene is composed of two distinguishable components: one CO 2-mediated and the other CO 2-independent. 相似文献
10.
Peak levels of 1-aminocyclopropane-l-carboxylic acid (ACC) in flower parts of ageing carnations ( Dianthus caryophyllus L. cv Scanea 3C) were detected 6 to 9 days after flower opening. The ethylene climacteric and the first visible sign of wilting was observed 7 days after opening. The concentration of conjugated ACC in these same tissues peaked at day three with reduction of 70% by day 4. From day 5 to day 9 all parts followed a diurnal pattern of increasing in conjugate levels 1 day and decreasing the next. Concentrations of conjugated ACC were significantly higher than those of ACC in all ageing parts. Preclimacteric petals treated with ACC or 1-(malonylamino)-cycloprane-1-carboxylic acid (MACC), started to senesce 30 to 36 hours after treatment. When petals were treated with MACC plus by 0.1 millimolar aminoethyoxyvinylglycine, premature senescence was induced, while ethylene production was suppressed relative to MACC-treated petals. Petals treated with MACC and silver complex produced ethylene, but did not senesce. The MACC-induced ethylene was inhibited by the addition of 1.0 millimolar CoC1 2. These results demonstrate MACC-induced senescence in preclimacteric petals. The patterns of ACC and MACC detected in the flower parts support the view that an individual part probably does not export an ethylene precursor to the remainder of the flower inducing senescence. 相似文献
11.
Using cotyledonary segments of cocklebur ( Xanthium pennsylvanicum Wallr. ) seeds, the inhibitory effect of α-aminoisobutyric acid (AIB) on ethylene production was compared with that of propyl gallate and CoCl 2. Of these inhibitors only AIB was effective in causing the accumulation of endogenous free 1-aminocyclopropane-l-carboxylic acid (ACC) in the tissue. The degree of inhibition of ethylene production by AIB decreased markedly with increasing concentrations of pre-loaded ACC, while the inhibition by propyl gallate and CoCl 2 changed little. Kinetic analysis showed that AIB competitively inhibited the conversion of pre-loaded ACC to ethylene, but propyl gallate and CoC l2 did not. Short-chain organic acids and analogues of AIB, such as acetic, propionic, butyric and cyclopropanecarboxylic acids, did not inhibit ethylene production by the segments. Thus, additional support for the competitive mode of inhibitory action of AIB on the conversion of free ACC to ethylene was provided. A conjugated hydrolysable ACC was found to be present in abundance in cotyledons of this seed. However, its content in the tissue was hardly affected by treatment with the three inhibitors and by administration of exogenous ACC, suggesting that the conjugated ACC was not directly involved in ethylene production. 相似文献
12.
Ethylene production and floral senescence following compatible and incompatible pollinations were studied in a self-incompatible species, Petunia inflata. Both compatible and incompatible pollinations resulted in a burst of ethylene synthesis that peaked 3 hours after pollination. P. inflata pollen was found to carry large amounts of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). The amount of pollen-held ACC varied in different genetic backgrounds, and the magnitude of the peak correlated with the amount of ACC borne by the pollen. Aminooxyacetic acid (AOA), an inhibitor of ACC synthesis, had no inhibitory effect on this ethylene response, indicating that pollen-borne ACC was largely responsible for the early synthesis of ethylene. After compatible pollination, a second increase in ethylene synthesis began at 18 hours, and the first sign of senescence appeared at 36 hours. Upon treatment with AOA, the second phase of ethylene production was reduced by 95%, indicating that endogenous ACC synthesis was required for this phase of ethylene synthesis. AOA treatment also delayed senescence to 6 days after anthesis. After incompatible pollination, a second increase in ethylene production did not occur until 3 days, and the first sign of senescence occurred 12 hours later. Unpollinated flowers showed an increase in ethylene production 3 to 4 days after anthesis and displayed signs of senescence 1 day later. The significance of the early and late phases of pollination-induced ethylene synthesis is discussed. 相似文献
13.
Exogenous ethylene stimulated ethylene production in intact citrus ( Citrus sinensis L. Osbeck cv. “Washington Navel”) leaves and leaf discs following a 24-hour exposure. Studies with leaf discs showed that ethylene production decreased when ethylene was removed by aeration. The extent of stimulation was dependent upon the concentration of exogenous ethylene (1-10 microliters per liter). Silver ion blocked the autocatalytic effect of ethylene at concentrations of 0.5 millimolar and lower, but increased ethylene production at higher concentrations. The stimulating effect of ethylene resulted from the enhancement of both 1-aminocyclopropane-1-carboxylic acid (ACC) formation and the conversion of ACC to ethylene. Whereas autocatalysis was evident following 24 hours incubation, autoinhibition of wound- and mannitol-induced ethylene production was observed during the first 24-hour incubation. Ethylene treatment during this period resulted in a marked decrease in ACC levels and ethylene production rates. Furthermore, in leaf discs treated for 24 hours with ethylene, ethylene production rates increased greatly during the first 2 hours after removal of exogenous ethylene by aeration. This increase was eliminated if the discs were transferred to propylene instead of air, indicating that the autocatalytic effect of ethylene is counteracted by its autoinhibitory effect. It is suggested that autocatalysis involves increased synthesis of ACC synthase and the enzyme responsible for the conversion of ACC to ethylene, whereas autoinhibition involves suppression of the activity of these two enzymes. 相似文献
14.
d-Galactose has been shown to have toxic and growth inhibitory effects in plants. When applied at levels of 50 millimolar to tobacco ( Nicotiana tabacum L. cv Xanthi) leaf discs galactose caused a rapid increase in ethylene production during the first 2 days of incubation, followed by a rapid return to the basal level on the third day. This pattern of galactose-stimulated ethylene production was accompanied by increased formation of 1-aminocyclopropane-1-carboxylic acid (ACC), which accumulated without being metabolized to ethylene or to the ACC-conjugate. The inhibitory effect of galactose (50 millimolar) on the conversion of ACC of ethylene was relieved partially by d-glucose or sucrose (50 millimolar), and completely by CO 2 (10%), which were shown to enhance this conversion by themselves. Consequently, application of galactose plus any one of these compounds increased ethylene production and decreased free ACC levels. The data suggest that galactose toxicity may result in both an increased ethylene production as well as in accumulation of free ACC in aged discs. The increased ethylene production rates and ACC levels may, in turn, play a role in the development of symptoms associated with galactose toxicity. 相似文献
15.
The evolution of ethylene, both from the endogenous source and from added 1-aminocyclopropane-1-carboxylic acid (ACC), has been followed in close relationship with the senescent loss of chlorophyll from seedling oat leaves. In white light, where chlorophyll loss is slow, the ethylene evolution increases slowly at first, but when the loss of chlorophyll becomes more rapid, ethylene evolution accelerates. CoCl 2 inhibits this increase and correspondingly maintains the chlorophyll content, with an optimum concentration of 10 micromolar. The rapid rate of chlorophyll loss in the dark is slightly decreased by 3-aminoethoxyvinyl glycine (AVG), by cobalt, and slightly stimulated by ACC. The slower chlorophyll loss in white light, however, is almost completely inhibited by silver ions, greatly decreased by cobalt and by AVG, and strongly increased by ACC. Since the chlorophyll loss is accompanied by proteolysis, it represents true senescence. Chlorophyll loss in light is also strongly antagonized by CO 2, 1% CO 2 giving almost 50% chlorophyll maintenance in controls, while in the presence of added ACC or ethylene gas, the chlorophyll loss is 50% reversed by about 3% CO 2. The ethylene system in leaves is thus more sensitive to CO 2 than that in fruits. Indoleacetic acid also clearly decreases the effect of ACC. It is shown that kinetin, CO 2, Ag +, and indoleacetic acid, all of which oppose the effect of ethylene, nevertheless increase the evolution of ethylene by the leaves, and it is suggested that ethylene evolution may, in many instances, mean that its hormonal metabolism is being prevented. 相似文献
16.
Hibiscus rosa- sinensis L. flowers (cv La France) senesce and die over a 12-h period after opening. The aim of this study was to examine the physiological
mechanisms regulating the senescence process of ephemeral hibiscus flowers. Different flower stages and floral organs were
used to determine whether any interaction existed during flower senescence between endogenous abscisic acid (ABA) and the
predisposition of the tissue to ethylene synthesis. This was carried out on whole flowers treated with promoters and inhibitors
of ethylene and ABA synthesis or a combination of them. Treatments with 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor
of ethylene biosynthesis, enhanced flower senescence, whereas amino-oxyacetic acid (AOA) and fluridone, an ethylene and an
ABA inhibitor, respectively, extended flower longevity. These effects were more significant when applied before anthesis.
Ethylene evolution was substantially reduced in all organs from open and senescent flowers treated with fluridone and AOA.
Similarly, endogenous ABA accumulation was negatively affected by AOA and fluridone treatments. Application of fluridone plus
ACC reduced ethylene evolution and increased ABA content in a tissue-specific manner but did not overcome the inhibitor effect
on flower longevity. AOA plus fluridone treatment slightly accelerated flower longevity compared to AOA-treated flowers. Application
of ABA alone promoted senescence, suppressed ethylene production, and, when applied with fluridone, countered the fluridone-induced
increase in flower longevity. Taken together, these results suggest that the senescence of hibiscus flowers is an endogenously
regulated ethylene- and ABA-dependent process. 相似文献
17.
Carnation tissue was allowed to vitrify in liquid culture and ethylene production, ACC content and capacity to convert ACC to ethylene were measured in comparison to tissue developing normally on solid medium. Flask atmospheres of liquid cultures accumulated ethylene at a higher rate during the first four days. Daily ethylene production by vitrifying material decreased later. Ethylene emission by vitrifying tissues always remained above controls when subcultured daily to fresh medium. Explants and microsomal preparations from vitrifying carnations converted ACC to ethylene at a higher degree from the first day in liquid medium. ACC level markedly increased in vitrifying tissues during the first two days of liquid culture. Raising the level of ethylene in the atmosphere of solid cultures did not induce vitrification symptoms nor did use of inhibitors of ethylene biosynthesis in liquid cultures prevent the process. The role of ethylene in vitrification is reappraised. 相似文献
18.
Ethylene production and expression patterns of an 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (CARAO1) and of two ACC synthase (EC 4.4.1.14) genes (CARACC3 and CARAS1) were studied in floral organs of cut carnation flowers (Dianthus caryophyllus L.) cv. White Sim. During the vase life and after treatment of fresh flowers with ethylene, production of ethylene and expression of ethylene biosynthetic genes first started in the ovary followed by the styles and the petals. ACC oxidase was expressed in all the floral organs whereas, during the vase life, tissue-specific expression of the two ACC synthase genes was observed. After treatment with a high ethylene concentration, tissue specificity of the two ACC synthase genes was lost and only a temporal difference in expression remained. In styles, poor correlation between ethylene production and ACC synthase (CARAS1) gene expression was observed suggesting that either activity is regulated at the translational level or that the CARAS1 gene product requires an additional factor for activity.Isolated petals showed no increase in ethylene production and expression of ethylene biosynthetic genes when excised from the flower before the increase in petal ethylene production (before day 7); showed rapid cessation of ethylene production and gene expression when excised during the early phase of petal ethylene production (day 7) and showed a pattern of ethylene production and gene expression similar to the pattern observed in the attached petals when isolated at day 8. The interorgan regulation of gene expression and ethylene as a signal molecule in flower senescence are discussed. 相似文献
19.
Mechanical perturbation (MP, gentle tubbing) promoted the senescence of detached oat ( Avena sativa L. cv. Victory) leaf segments in the dark. The promotion of senescence increased with increase in the number of rubbings and could be seen after 24 h of dark incubation; the maximum effect was reached on day 3. The effect (% of control) of MP on the loss of protein was greater than the effect on chlorophyll (Chl) loss on day 1. However, on day 3 the effect of MP on the loss of Chl became greater than the effect on the loss of protein. Ethephon and 1-aminocyclopropane-1-carboxylic acid (ACC) marginally promoted the loss of Chl by both control and rubbed oat leaf segments, and the effect was additive with MP. Chloramphenicol (CAP), spermine, aminoethoxyvinylglycine (AVG) and Ca 2+ marginally delayed the loss of Chl and protein in both control and rubbed segments. Kinetin greatly retarded the senescence of all segments. Even in the presence of these substances, the amounts of Chl and protein in the rubbed segments were always less than in their respective controls, thus retaining the effect of the MP. However, abscisic acid (ABA) and cycloheximide (CHI) caused the rubbed oat leaf segments to retain more Chl and protein than their respective control segments. The effect of CHI was actually enhanced by MP. Rubbing promoted the senescence of attached leaves of oats ( Avena sativa L. cv. Victory), maize ( Zea mays L. cv. Early Belle) and pumpkin ( Cucurbita pepo L. cv. Jack-o-lantern) cotyledons in the dark. Rubbing promoted the senescence of oat leaf segments even in light, although to a lesser extent compared to the effect in the dark. The senescence of leaves of pumpkin and cocklebur ( Xanthium strumarium Wallr. var. Pennsylvanicum ) in situ was also enhanced by MP. 相似文献
20.
To better understand the physiological roles of brassinosteroids (BRs) in the primary roots of maize, we examined their effect
on ethylene production. Exogenously applied brassinolide (BL; 10 -9 to 10 -7 M) incrementally increased the level ethylene in a dose-dependent manner. This BL-induced production was enhanced in the
presence of IAA, thereby implying a synergistic effect between BR and IAA. At 10 -7 M BL, the level of free ACC was increased, but that of conjugated ACC was diminished. Moreover, greater concentrations of
BL proportionally increased ACC oxidase activity. In contrast, higher levels of IAA increased the endogenous content of conjugated
ACC as well as ACC synthase activity. Based on these results, we conclude that BR activates ethylene production mainly via
ACC oxidase, and interacts with IAA to produce ethylene. However, the functional site for ethylene production is different
for each hormone. 相似文献
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