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S F Yang

Publications and source records attributed to S F Yang.

At least 109 records · Page 6Linked to original sources
PubMed1981

Biosynthesis of stress ethylene induced by water deficit.

Wheat leaves normally produced very little ethylene, but following a water deficit stress which caused a loss of 9% initial fresh weight, ethylene production increased more than 30-fold within 4 hours and declined rapidly thereafter. The changes in ethylene production were paralleled by an increase and subsequent decrease in 1-aminocyclopropanecarboxylic acid (ACC) content. The level of S-adenosylmethionine was unaffected, suggesting that the conversion of S-adenosylmethionine to ACC is a key reaction in the production of water stress-induced ethylene. This view was further supported by the observation that application of ACC to nonstressed leaf tissue caused a 70-fold increase in ethylene production, while aminoethoxyvinylglycine, a known inhibitor of the conversion of S-adenosylmethionine to ACC, inhibited ACC accumulation as well as the surge in ethylene production if the inhibitor was applied prior to the stress treatment. Cycloheximide, an inhibitor of protein synthesis, effectively blocked both ethylene production and ACC formation, suggesting that water stress induces de novo synthesis of ACC synthase, which is the rate-controlling enzyme in the pathway of ethylene biosynthesis.

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PubMed1980

Xylem Transport of 1-Aminocyclopropane-1-carboxylic Acid, an Ethylene Precursor, in Waterlogged Tomato Plants.

Waterlogging is known to cause an increase in ethylene synthesis in the shoot which results in petiole epinasty. Evidence has suggested that a signal is synthesized in the anaerobic roots and transported to the shoot where it stimulates ethylene synthesis. Experimental data are presented showing that 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, serves as the signal. Xylem sap was collected from detopped tomato plants (Lycopersicon esculentum Mill. cv. VFN8). ACC in the sap was quantitated by a sensitive and specific assay, and its tentative chemical identity verified by paper chromatography. ACC levels in both roots and xylem sap increased markedly in response to waterlogging or root anaerobiosis. The appearance of ACC in the xylem sap of flooded plants preceded both the increase in ethylene production and epinastic growth, which were closely correlated. Plants flooded and then drained showed a rapid, simultaneous drop in ACC flux and ethylene synthesis rate. ACC supplied through the cut stem of tomato shoots at concentrations comparable to those found in xylem sap caused epinasty and increased ethylene production. These data indicate that ACC is synthesized in the anaerobic root and transported to the shoot where it is readily converted to ethylene.

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PubMed1980

Stress-induced Ethylene Production in the Ethylene-requiring Tomato Mutant Diageotropica.

Ethylene synthesis in vegetative tissues is thought to be controlled by indoleacetic acid (IAA). However, ethylene synthesis in the diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) was much less sensitive to IAA than in the normal variety (VFN8). Yet, mechanical wounding stimulated ethylene production by the mutant. The dgt tomato provides an opportunity to study the regulation of stress ethylene independent of IAA effects. Waterlogging (i.e. anaerobic stress) stimulated production of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), in the roots. The ACC was transported to the shoot where it was converted to ethylene. The dgt mutant efficiently utilized ACC for ethylene synthesis under aerobic conditions. The results confirm that the genetic lesion in dgt is located at a step prior to the formation of ACC. Furthermore, induction of ethylene synthesis by anaerobic or mechanical stresses in this mutant is independent of IAA action.

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PubMed1980

Biosynthesis of wound ethylene.

Untreated mung bean hypocotyls produced very little C(2)H(4) but, upon treatment with 10 millimolar Cu(2+) or 10 millimolar Cu(2+) + 10 millimolar Ca(2+), C(2)H(4) production increased 20- and 40-fold, respectively, within 6 hours. This increase in C(2)H(4) production was preceded and paralleled by an increase in 1-aminocyclopropanecarboxylic acid (ACC) content, but the level of S-adenosylmethionine (SAM) was unaffected, suggesting that the conversion of SAM to ACC is a key reaction in the production of wound-induced C(2)H(4). This view was further supported by the observation that application of aminoethoxyvinylglycine, a known inhibitor of the conversion of SAM to ACC, eliminated the increases in ACC formation and in C(2)H(4) production. A significant increase in C(2)H(4) production was observed in the albedo tissue of orange in response to excision, and it was paralleled by an increase in ACC content. In columella tissue of unripe green tomato fruit, massive increases in the C(2)H(4) production rate (from 0 to 12 nanoliters per gram per hour), in ACC content (from 0.05 to 12 nmoles per gram), and in ACC synthase activity (from 0 to 6.4 units per milligram protein) occurred during the 9-hour incubation period following excision. Infiltration with 0.1 millimolar cycloheximide, an inhibitor of protein synthesis, completely blocked wound-induced C(2)H(4) production, ACC formation, and development of ACC synthase activity. These data indicate that wounding induces the synthesis of ACC synthase, which is the rate-controlling enzyme in the pathway of C(2)H(4) biosynthesis and, thereby, causes accumulation of ACC and increase in C(2)H(4) production.

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PubMed1980

Inhibition of ethylene production by 2,4-dinitrophenol and high temperature.

2,4-Dinitrophenol (DNP) and high temperature (35 to 40 C) are known to inhibit C(2)H(4) production in various plant tissues. The present study was made to determine the step in the C(2)H(4) biosynthetic pathway (methionine --> S-adenosylmethionine [SAM] --> 1-aminocyclopropane-1-carboxylic acid [ACC] --> C(2)H(4)) at which these treatments exert their inhibitory effect. In mung bean hypocotyls the dose-inhibition curves for the effect of DNP on auxin-dependent C(2)H(4) production (in which auxin exerts its effect by stimulating the conversion of SAM to ACC) and on ACC-dependent C(2)H(4) production (in which ACC is directly utilized as precursor) were similar. It was concluded, therefore, that DNP at low concentrations (below 50 micromolar) exerted its effect primarily on the conversion of ACC to C(2)H(4), a step which is common to both systems. This view was further substantiated by quantitative analysis of the intermediates in the biosynthetic sequence. DNP exerted little influence on the content of SAM but caused a significant increase in the ACC content and marked inhibition in C(2)H(4) production, indicating that the conversion of ACC to C(2)H(4) is the crossover point. At higher concentrations (above 100 micromolar), DNP inhibited the conversion of methionine to ACC and to C(2)H(4), and this effect could be attributed to the inhibition of SAM synthesis.The optimal temperature for maximal C(2)H(4) production by apple tissue and mung bean hypocotyl is about 30 C. An increase in temperature to 35 C caused an accumulation of endogenous ACC, whereas C(2)H(4) production was greatly reduced. These results suggest that the conversion of ACC to C(2)H(4) is highly vulnerable to high temperature inhibition.

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PubMed1979

Ethylene biosynthesis: Identification of 1-aminocyclopropane-1-carboxylic acid as an intermediate in the conversion of methionine to ethylene.

L-[U-(14)C]Methionine fed to apple tissue was efficiently converted to ethylene when the tissue was incubated in air. In nitrogen, however, it was not metabolized to ethylene but was instead converted to 1-aminocyclopropane-1-carboxylic acid (ACC). When apple tissues were fed with L-[methyl-(14)C]methionine or L-[(35)S]methionine and incubated in nitrogen, radioactivity was found subsequently in methylthioribose. This suggests that methionine is first converted to S-adenosylmethionine which is in turn fragmented to ACC and methylthioadenosine. Methylthioadenosine is then hydrolyzed to methylthioribose. The conclusion that ACC is an intermediate in the conversion of methionine to ethylene is based on the following observations: Labeled ACC was efficiently converted to ethylene by apple tissue incubated in air; the conversion of labeled methionine to ethylene was greatly decreased in the presence of unlabeled ACC, but the conversion of labeled ACC to ethylene was little affected by the presence of unlabeled methionine; and 2-amino-4-(2'-aminoethoxy)trans-3-butenoic acid, a potent inhibitor of pyridoxal phosphate-mediated enzyme reactions, greatly inhibited the conversion of methionine to ethylene but did not inhibit conversion of ACC to ethylene. These data indicate the following sequence for the pathway of ethylene biosynthesis in apple tissue: methionine --> S-adenosylmethionine --> ACC --> ethylene. A possible mechanism accounting for these reactions is presented.

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PubMed1979

Ethylene and Ethane Production from Sulfur Dioxide-injured Plants.

After alfalfa (Medicago sativa) seedlings were exposed to approximately 0.7 microliter per liter SO(2) for 8 hours, elevated ethylene and ethane production was observed. Ethylene production peaked about 6 hours and returned to control levels by about 24 hours following the fumigation, while ethane production peaked about 36 hours and was still above control levels 48 hours after the fumigation. Light had an opposite effect upon the production of the two gases: ethane production rates were higher from plants held in light, whereas ethylene production rates were higher from those held in the dark. Peak ethylene and ethane production rates from SO(2)-treated plants were about 10 and 4 to 5 times greater, respectively, than those of the control plants. Ethylene appeared to be formed primarily from stressed yet viable leaves and ethane from visibly damaged leaves. The different time courses and light requirements for ethylene and ethane production suggest that these two gases were formed via different mechanisms. Light appears to have a dual role. It enhances SO(2)-induced cellular damage and plays a role for repairs.

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PubMed1979

Regulation of Auxin-induced Ethylene Production in Mung Bean Hypocotyls: Role of 1-Aminocyclopropane-1-Carboxylic Acid.

Ethylene production in mung bean hypocotyls was greatly increased by treatment with 1-aminocyclopropane-1-carboxylic acid (ACC), which was utilized as the ethylene precursor. Unlike auxin-stimulated ethylene production, ACC-dependent ethylene production was not inhibited by aminoethoxyvinylglycine, which is known to inhibit the conversion of S-adenosylmethionine to ACC. While the conversion of methionine to ethylene requires induction by auxin, the conversion of methionine to S-adenosylmethionine and the conversion of ACC to ethylene do not. It is proposed that the conversion of S-adenosylmethionine to ACC is the rate-limiting step in the biosynthesis of ethylene, and that auxin stimulates ethylene production by inducing the synthesis of the enzyme involved in this reaction.

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PubMed1979

Auxin-induced Ethylene Production and Its Inhibition by Aminoethyoxyvinylglycine and Cobalt Ion.

Auxin is known to stimulate greatly both C(2)H(4) production and the conversion of methionine to ethylene in vegetative tissues, while amino-ethoxyvinylglycine (AVG) or Co(2+) ion effectively block these processes. To identify the step in the ethylene biosynthetic pathway at which indoleacetic acid (IAA) and AVG exert their effects, [3-(14)C]methionine was administered to IAA or IAA-plus-AVG-treated mung bean hypocotyls, and the conversion of methionine to S-adenosylmethionine (SAM), 1-amino-cyclopropane-1-carboxylic acid (ACC), and C(2)H(4) was studied. The conversion of methionine to SAM was unaffected by treatment with IAA or IAA plus AVG, but active conversion of methionine to ACC was found only in tissues which were treated with IAA and which were actively producing ethylene. AVG treatment abolished both the conversion of methionine to ACC and ethylene production. These results suggest that in the ethylene biosynthetic pathway (methionine --> SAM --> ACC --> C(2)H(4)) IAA stimulates C(2)H(4) production by inducing the synthesis or activation of ACC synthase, which catalyzes the conversion of SAM to ACC. Indeed, ACC synthase activity was detected only in IAA-treated tissues and its activity was completely inhibited by AVG. This conclusion was supported by the observation that endogenous ACC accumulated after IAA treatment, and that this accumulation was completely eliminated by AVG treatment. The characteristics of Co(2+) inhibition of IAA-dependent and ACC-dependent ethylene production were similar. The data indicate that Co(2+) exerts its effect by inhibiting the conversion of ACC to ethylene. This conclusion was further supported by the observation that when Co(2+) was administered to IAA-treated tissues, endogenous ACC accumulated while ethylene production declined.

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PubMed1978

Inactivity of Oxidation Products of Indole-3-acetic Acid on Ethylene Production in Mung Bean Hypocotyls.

The suggestion that indole-3-acetic acid (IAA)-stimulated ethylene production is associated with oxidative degradation of IAA and is mediated by 3-methyleneoxindole (MOI) has been tested in mung bean (Phaseolus aureus Roxb.) hypocotyl segments. While IAA actively stimulated ethylene production, MOI and indole-3-aldehyde, the major products of IAA oxidation, were inactive. Tissues treated with a mixture of intermediates of IAA oxidation, obtained from a 1-hour incubation of IAA with peroxidase, failed to stimulate ethylene production. Furthermore, chlorogenic acid and p-coumaric acid, which are known to interfere with the enzymic oxidation of IAA to MOI, had no effect on IAA-stimulated ethylene production. Other oxidation products of IAA, including oxindole-3-acetic acid, indole-3-carboxylic acid, (2-sulfoindole)-3-acetic acid, and dioxindole-3-acetic acid, were all inactive. 1-Naphthaleneacetic acid was as active as IAA in stimulating ethylene production but was decarboxylated at a much lower rate than IAA, suggesting that oxidative decarboxylation of auxins is not linked to ethylene production. These results demonstrate that IAA-stimulated ethylene production in mung bean hypocotyl tissue is not mediated by MOI or other associated oxidative products of IAA.

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PubMed1978

Induction of phenylalanine ammonia-lyase and increase in phenolics in lettuce leaves in relation to the development of russet spotting caused by ethylene.

Russet spotting (RS), consisting of numerous small brown spots on the midrib of head lettuce (Lactuca sativa), is a physiological disorder induced by exposure to ethylene. In leaves suffering RS, the increase in spotting was accompanied by a parallel increase in the amount of phenolic compounds. Of these, chlorogenic acid and isochlorogenic acid were identified. Ethylene induced high phenylalanine ammonia-lyase (PAL) activity and RS formation in the susceptible cultivar Salinas, but not in the resistant cultivar Calmar. In the absence of ethylene neither significant PAL induction nor RS occurred. No correlation was found between the increase in polyphenol oxidase or peroxidase and the development of RS. The increase in PAL activity, however, was closely correlated with the development of RS. The increase in PAL activity preceded the development of RS, and the extent of RS was directly related to the level of PAL. Three temperatures (0.5, 5.5, and 12.5 C) were compared on the basis of their influence on both RS and PAL induction. At the lowest temperature (0.5 C) neither PAL induction nor RS occurred to a significant extent. At the highest temperature (12.5 C) an initial rapid increase in PAL activity and an earlier development of spotting were observed, but subsequently there was a decrease in both PAL activity and the rate of development of RS. At the medium temperature (5.5 C) both PAL activity and RS increased progresively with time. The decline of PAL activity at a higher temperature might be attributed to inactivation of the enzyme. Thus, a temperature favorable for induction of PAL activity by ethylene was also favorable for RS. These observations indicate a close interrelationship between the induction of PAL activity and the development of RS in response to ethylene, and suggest a causal relationship between the two events. PAL serves as a useful biochemical marker for the RS reaction.

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PubMed1977

Albumin synthesis in mouse uterus in response to liver mRNA.

Messenger RNA was isolated, by means of its attachment to poly(A), from calf liver and the livers of mice, rats, and chickens. When injected into the uterine lumen of immature or spayed mice, both mouse albumin and the albumins characteristic of the species donating the mRNA were synthesized. Studies with inhibitors disclosed that puromycin blocked the synthesis of both albumin species, while dactinomycin affected only mouse albumin synthesis. It appears, therefore, that in the experimental situation used, the function of exogenous liver mRNA is 2-fold: (i) it programs the synthesis of alien albumin in uterine epithelial cells, and (ii) it stimulates the synthesis of mRNA in epithelial cells. The mRNA thus produced primes the synthesis of mouse albumin.

Albumins↗
PubMed1977

Chlorophyll destruction by the bisulfite-oxygen system.

Destruction of chlorophyll, as determined by the loss in absorbance at 665 nm, occurred in two in vitro systems in the presence of bisulfite in 76% ethanol. The first system required light and O(2) in addition to bisulfite and exhibited an optimum pH of 4. Chlorophyll functioned as a photosensitizer and there was little chlorophyll destruction occurring above pH 5. With 286 mueinsteins m(-2) irradiation, approximately 80% of the chlorophyll was destroyed in three minutes. In the second system, chlorophyll destruction in the presence of bisulfite occurred in the dark and required Mn(2+), O(2), and glycine. Destruction of chlorophyll in this system was much more rapid than in the light system with approximately 70% destruction occurring in two seconds. In both systems, chlorophyll destruction was linked to bisulfite oxidation. The free radical scavengers hydroquinone, butylated hydroxytoluene, 1,2-dihydroxybenzene-3,5-disulfonic acid, and alpha-tocopherol were effective in inhibiting the destruction of chlorophyll in both systems. The singlet O(2) scavengers, 2,5-dimethylfuran and 1,3-diphenylisobenzofuran, were ineffective inhibitors and beta-carotene only slightly effective when tested in the light system. The evidence suggests that in these two systems chlorophyll was destroyed by free radicals, probably superoxide radical, which was produced during the aerobic oxidation of bisulfite.

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PubMed1977

Methionine metabolism in apple tissue: implication of s-adenosylmethionine as an intermediate in the conversion of methionine to ethylene.

If S-adenosylmethionine (SAM) is the direct precursor of ethylene as previously proposed, it is expected that 5'-S-methyl-5'-thioadenosine (MTA) would be the fragment nucleoside. When [Me-(14)C] or [(35)S]methionine was fed to climacteric apple (Malus sylvestris Mill) tissue, radioactive 5-S-methyl-5-thioribose (MTR) was identified as the predominant product and MTA as a minor one. When the conversion of methionine into ethylene was inhibited by (l)-2-amino-4-(2'-aminoethoxy)-trans-3-butenoic acid, the conversion of [(35)S] or [Me(14)C]methionine into MTR was similarly inhibited. Furthermore, the formation of MTA and MTR from [(35)S]methionine was observed only in climacteric tissue which produced ethylene and actively converted methionine to ethylene but not in preclimacteric tissue which did not produce ethylene or convert methionine to ethylene. These observations suggest that the conversion of methionine into MTA and MTR is closely related to ethylene biosynthesis and provide indirect evidence that SAM may be an intermediate in the conversion of methionine to ethylene.When [(35)S]MTA was fed to climacteric or preclimacteric apple tissue, radioactivity was efficiently incorporated into MTR and methionine. However, when [(35)S]MTR was administered, radioactivity was efficiently incorporated into methionine but not MTA. This suggests that the sulfur of MTA is incorporated into methionine via MTR. A dual label experiment with [(35)S, Me-(3)H]MTA indicates that the CH(3)S group of MTA was transferred as a unit to form methionine.A scheme is presented for the production of ethylene from methionine, the first step being the activation of methionine by ATP to give SAM. SAM is fragmented to give ethylene, MTA, and other products. MTA is then hydrolyzed to MTR which donates its methylthio group to a four-carbon acceptor to reform methionine.

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PubMed1976

Stimulation of ethylene production in the mung bean hypocotyls by cupric ion, calcium ion, and kinetin.

The synergistic stimulation of ethylene production by kinetin and Ca(2+) in hypocotyl segments of mung bean (Phaseolus aureus Roxb.) seedling was further studied. The requirement for Ca(2+) in this system was specific. Except for Sr(2+), which mimicked the effect of Ca(2+), none of the following divalent cations, including Ba(2+), Mg(6+), Cu(2+), Hg(2+), Co(2+), Ni(2+), Sn(2+), and Zn(2+), showed synergism with kinetin on ethylene production. Fe(2+), however, showed a slight synergism with kinetin. Some of them (Hg(2+), Co(2+), and Ni(2+)) had a strong inhibitory effect, while others (Zn(2+), Mg(2+), Sn(2+), and Ba(2+)) had a slight or no inhibitory effect on ethylene production in the absence or presence of kinetin.Cu(2+) alone, depending on the concentration applied, stimulated ethylene production with a lag period of about 2 hours and had no synergism with kinetin on ethylene production. When Cu(2+) was applied with Ca(2+), a remarkable synergistic stimulation of ethylene production was observed. Tracer experiments indicated that Cu(2+) enhanced the uptake of (45)Ca(2+) into the tissues during the first few hours of incubation, and this increase of (45)Ca(2+) uptake paralleled the enhancement of ethylene production. When Ca(2+) was applied together with kinetin plus Cu(2+), both the ethylene production and the (45)Ca(2+) uptake were greatly increased over those from the segments treated with Cu(2+) or kinetin alone. The increase in ethylene production as a result of kinetin plus Ca(2+) plus Cu(2+) treatment is equal to the combined increases caused by kinetin plus Ca(2+) and Cu(2+) plus Ca(2+). A possible mechanism accounting for such cooperative effects of Cu(2+), Ca(2+), and kinetin on ethylene production is discussed.

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PubMed1976

Inhibition of ethylene production by cobaltous ion.

The effect of Co(2+) on ethylene production by mung bean (Phaseolus aureus Roxb.) and by apple tissues was studied. Co(2+), depending on concentrations applied, effectively inhibited ethylene production by both tissues. It also strongly inhibited the ethylene production induced by IAA, kinetin, IAA plus kinetin, Ca(2+), kinetin plus Ca(2+), or Cu(2+) treatments in mung bean hypocotyl segments. While Co(2+) greatly inhibited ethylene production, it had little effect on the respiration of apple tissue, indicating that Co(2+) does not exert its inhibitory effect as a general metabolic inhibitor. Ni(2+), which belongs to the same group as Co(2+) in the periodic table, also markedly curtailed both the basal and the induced ethylene production by apple and mung bean hypocotyl tissues.In a system in which kinetin and Ca(2+) were applied together, kinetin greatly enhanced Ca(2+) uptake, thus enhancing ethylene production. Co(2+), however, slightly inhibited the uptake of Ca(2+) but appreciably inhibited ethylene production, either in the presence or in the absence of kinetin. Tracer experiments using apple tissue indicated that Co(2+) strongly inhibited the in vivo conversion of l-[U-(14)C]methionine to (14)C-ethylene. These data suggest that Co(2+) inhibited ethylene production by inhibiting the conversion of methionine to ethylene, a common step which is required for ethylene formation by higher plants.Co(2+) is known to promote elongation, leaf expansion, and hook opening in excised plant parts in response to applied auxins or cytokinins. Since ethylene is known to inhibit these growth phenomena, it is suggested that Co(2+) exerts its promotive effect, at least in part, by inhibiting ethylene formation.

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