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Differential screening, aimed at the isolation of cDNA clonesof mRNAs whose accumulation is influenced by GA3, resulted inthe isolation of a cDNA clone of an mRNA whose level was decreasedby GA3 in segments of epicotyls of Vigna angularis. The putativeprotein encoded by this cDNA resembled the 1-aminocyclopropane-l-carbox-ylateoxidases (ACC oxidases) identified in other plant species (about80% homology at the amino acid level). Thus, the correspondinggene was designated AB-ACO1 (azuki bean ACC oxidase). GA3 alsodecreased the activity of ACC oxidase in azuki bean epicotyls,but it did not decrease the rate of ethylene evolution. In fact,GA3 increased the rate of ethylene evolution and the level ofACC. Thus, GA3 seemed to increase the production of ethyleneby promoting the synthesis of ACC. (Received January 10, 1997; Accepted July 31, 1997) 相似文献
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GRODZINSKI BERNARD; BOESEL INGRID; HORTON ROGER F. 《Journal of experimental botany》1982,33(2):344-354
The release of ethylene into sealed Erlenmeyer flasks by intactleaves and leaf discs of Xanthium strumarium L. a C3 plant andZea mays L. a C4 plant were compared both in white light andin darkness. The effects of the presence or absence of addedCO2 (in the form of sodium bicarbonate) the photosynthetic inhibitor3-[3,4-dichlorophenyl]-l, l-dimethyl urea (DCMU) and 1-aminocyclopropane-1-carboxylicacid (ACC), the precursor of ethylene in higher plants, werealso investigated. The rate of ethylene release from leaf tissue of Xanthium inthe absence of added CO2 was markedly reduced in the light (i.e.at the CO2 compensation point). Treatments that would enhancethe CO2 availability to the tissue (i.e. added bicarbonate,darkness, treatment with DCMU) allowed higher levels of ethylenerelease. Incubation of the tissue with ACC considerably enhancedthe release of ethylene compared to that from the correspondingcontrol tissue without ACC. However, the pattern of ethylenerelease induced by the various treatments was similar with orwithout added ACC. When tissue, in the absence of added CO2, was transferred fromlight to darkness, and back to light for 90 min periods, theethylene release rates Increased during the interposed darkperiod but resumed the lower rate during the final light period.The addition of CO2 in the light resulted in a similar rateof ethylene release to that found in the dark. The overall pattern of ethylene release from Zea leaf tissuesubjected to light and dark in the presence or absence of addedCO2 was similar to that of Xanthium. However, two or three timesmore ethylene was released from maize leaves in the light whenCO2 was added compared to that generated in the dark. This isin marked contrast to Xanthium, where, under the light conditionsused, the ethylene release rate in the dark equalled or exceededthat occurring in the light, even in the presence of high levelsof CO2. A very low rate of ethylene release was observed atthe CO2 compensation point of maize. A speculative model is presented to explain how photosyntheticactivity might act as a key factor in regulating ethylene evolutionfrom leaf tissue in these experiments. It invokes the conceptof an inhibition by CO2 of ethylene retention or breakdown thuspermitting more ethylene to be released from the leaves. 相似文献
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Inactivation of 1-aminocyclopropane-1-carboxylate (ACC) oxidase 总被引:1,自引:0,他引:1
Smith Julian J.; Zhang Zhi Hong; Schofield Christopher J.; John Philip; Baldwin Jack E. 《Journal of experimental botany》1994,45(5):521-527
The enzyme 1-aminocyclopropane-1-carboxylate (ACC) oxidase,which catalyses the final step in the biosynthesis of ethylene,showed a non-linear time-course in vitro and activity decayedwith a half-life of around 14 min. This loss of activity wasstudied using tomato ACC oxidase purified from Escherichia coiltransformed with the cDNA clone pTOM13. Inactivation was notdue to end-product inhibition by dehydroascorbic acid or cyanide.Preincubatlon of enzyme in the combined presence of Fe2+ ascorbateand ACC, which together allowed catalytic turnover, resultedin almost total loss of ACC oxidase activity. Enzyme Inactivatedby catalysis could not be reactivated by passage through SephadexG-25 or by treating with combina tions of DTT and CO2 A non-lineartime-course and inactivation in the presence of all substratesand cofactors was also shown for the enzyme assayed in vivowith melon fruit discs. Using the purified tomato enzyme a distinctascorbate-dependent inactivation was also observed, which occurredIn the absence of catalysis and was prevented, although notreversed, by catalase. This ascorbate-dependent inactivationmay thus be due to H2O2 attack on ACC oxidase. Key words: 1-aminocyclopropane-1-carboxylate (ACC) oxidase, catalase, catalytic inactivation, ethylene 相似文献
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Dunlap, J. R. 1988. Regulation of ACC-dependent ethylene productionby excised leaves from normal and albino Zea mays L. seedlings.J.exp. Bot. 39: 10791089. Albino corn (Zea mays L.) seedlings lacking natural leaf pigmentswere obtained by germinating seeds treated with fluridone, aninhibitor of carotenoid biosynthesis. Basal rates of ethyleneproduction were less than 2.0 nl g1 fr. wt h1in both treated (albino) and untreated (normal) leaves but increasedby 10- to 20-fold in the presence of added ACC. ACC-dependentethylene production (ADEP) was inhibited by cobalt or cyanideions and stimulated by NaHCO3, CO2 and light. ADEP in both tissueswas stimulated by glucose, fructose, galactose and sucrose.The accumulation of respiratory CO2 did not account for thecarbohydrate response. The decline in the ADEP characteristicof albino leaf tissue was slowed by incubation in the presenceof sucrose. IAA and ABA stimulated ADEP in normal leaves butinhibited ADEP in albino leaves. Sucrose-stimulated ADEP wasinhibited in albino leaf tissue treated with IAA or ABA indicatinga possible role for the chloroplast in carbohydrate-facilitatedADEP. However, results from this study suggest that chloroplastsperform a function in the regulation of ethylene productionby leaf tissue that extends beyond merely influencing internallevels of CO2. In the absence of detectable ACC, EFE was responsiblefor the entire series of responses expressed in regulation ofethylene biosynthesis by corn seedling leaf tissue. Key words: Corn, ethylene, sugars, phytohormones 相似文献
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Kosugi Yusuke; Oyamada Naoko; Satoh Shigeru; Yoshioka Toshihito; Onodera Ei-ichi; Yamada Yuko 《Plant & cell physiology》1997,38(3):312-318
We partially purified 1-aminocyclopropane-l-carboxy-late (ACC)oxidase from senescing petals of carnation {Dianthus caryophyllusL. cv. Nora) flowers and investigated its general characteristics,and, in particular, the inhibition of its activity by ACC analogs.The enzyme had an optimum pH at 7-7.5 and required Fe2+, ascorbateand NaHCO3 for its maximal activity. The Km for ACC was calculatedas 111-125 µM in the presence of NaHCO3. Its Mr was estimatedto be 35 and 36 kDa by gel-filtration chromatography on HPLCand SDS-PAGE, respectively, indicating that the enzyme existsin a monomeric form. These properties were in agreement withthose reported previously with ACC oxidases from different planttissues including senescing carnation petals. Among six ACCanalogs tested, l-aminocyclobutane-l-carboxylate (ACBC) inhibitedmost severely the activity of ACC oxidase from carnation petals.ACBC acted as a competitive inhibitor with the Ki of 20-31 µM.The comparison between the Km for ACC and the Ki for ACBC indicatedthat ACBC had an affinity which was ca. 5-fold higher than thatof ACC. Whereas ACC inactivated carnation ACC oxidase in a time-dependentmanner during incubation, ACBC did not cause the inactiva-tionof the enzyme. Preliminary experiments showed that ACBC andits N-substituted derivatives delayed the onset of senescencein cut carnation flowers. (Received August 19, 1996; Accepted November 26, 1996) 相似文献
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Characterization and Induction of the Activity of 1-Aminocyclopropane-1-Carboxylate Oxidase in the Wounded Mesocarp Tissue of Cucurbita maxima 总被引:4,自引:0,他引:4
Hyodo Hiroshi; Hashimoto Chise; Morozumi Shingo; Hu Wenzhong; Tanaka Kuniaki 《Plant & cell physiology》1993,34(5):667-671
1-Aminocyclopropane-1-carboxylate (ACC) oxidase (ethylene-formingenzyme) was isolated from wounded mesocarp tissue of Cucurbitamaxima (winter squash) fruit, and its enzymatic properties wereinvestigated. The enzyme required Fe2+ and ascorbate for itsactivity as well as ACC and O2 as substrates. The in vitro enzymeactivity was enhanced by CO2. The apparent Km value for ACCwas 175 µM under atmospheric conditions. The enzyme activitywas inhibited by sulfhydryl inhibitors and divalent cationssuch as Co2+, Cu2+, and Zn2+. ACC oxidase activity was induced at a rapid rate by woundingin parallel with an increase in the rate of ethylene production.The exposure of excised discs of mesocarp to 2,5-norbornadiene(NBD),an inhibitor of ethylene action, strongly suppressed inductionof the enzyme, and the application of ethylene significantlyaccelerated the induction of the activity of ACC oxidase inthe wounded mesocarp tissue. These results suggests that endogenousethylene produced in response to wounding may function in promotingthe induction of ACC oxidase. (Received January 13, 1993; Accepted April 15, 1993) 相似文献
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Activities of photosynthetic and photorespiratory enzymes viz.,ribulose bisphosphate carboxylase, phosphoenol pyruvate carboxylaseand glycolate oxidase from jute (Corchorus olitorius L.; cv.JRO 632) leaves were compared with those from maize (C4) andsunflower (C3) leaves. The photosynthetic CO2 fixation products,the release of 14CO2 in light and dark following photosynthesisin 14CO2, chlorophyll a: b ratio, gross leaf photosyntheticrate and dry matter production rate were also studied. The resultsshow that jute is a C3 plant. Key words: Jute, Corchorus olitorius, C3 photosynthesis 相似文献
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ROMERO-ARANDA R.; BONDADA B. R.; SYVERTSEN J. P.; GROSSER J. W. 《Annals of botany》1997,79(2):153-160
The effect of tetraploidy on leaf characteristics and net gasexchange was studied in diploid (2x ) and autotetraploid (4x) Valencia sweet orange (Citrus sinensis (L.)Osb.) and Femminello lemon (Citrus limon (L.)Burm. f.) leaves. Comparisons between ploidy levels were madeunder high irradiance (I) in a growth chamber or low total Iin a glasshouse. Tetraploids of both species had thicker leaves,larger mesophyll cell volume and lower light transmittance thandiploids regardless of growth I. Mesophyll surface area perunit leaf area of 2x leaves was 515% greater than on4x leaves. Leaf thickness and mesophyll cell volume were greaterin high I leaves than low I leaves. In high I, average leafarea was similar for 2x and 4x leaves, whereas in low I it was30% greater in 4x than in 2x leaves. Nitrogen and chlorophyllconcentration per cell increased with ploidy level in both growthconditions. The ratio of chlorophyll a:b was 25% greater in2x than in 4x leaves. When net CO2assimilation rate (ACO2) wasbased on leaf area, 4x orange leaves had 2435% lowerACO2than their diploids. There were no significant differencesin ACO2between 2x and 4x orange or lemon leaves when expressedon a per cell basis. Overall, lower ACO2per unit leaf area oftetraploids was related to increase in leaf thickness, largermesophyll cell volume, the decrease in mesophyll area exposedto internal air spaces, and the lower ratio between cell surfaceto cell volume. Such changes probably increased the resistanceto CO2diffusion to the site of carboyxlation in the chloroplasts. Cell volume; chlorophyll; irradiance; leaf thickness; nitrogen; photosynthesis; ploidy; Citrus limon ; C. sinensis ; Valencia sweet orange; Femminello lemon 相似文献
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Relationship between Leaf Structure and Gas Exchange in Wheat Leaves at Different Insertion Levels 总被引:3,自引:0,他引:3
Net photosynthesis rate (Pn), stomatal conductance to CO2 andresidual conductance to CO2 were measured in the last six leaves(the sixth or flag leaf and the preceding five leaves) of Triticumaestivum L. cv. Kolibri plants grown in Mediterranean conditions.Recently fully expanded leaves of well-watered plants were alwaysused. Measurements were made at saturating photosynthetic photonflux density, and at ambient CO2 and O2 levels. The specificleaf area, total organic nitrogen content, some anatomical characteristics,and other parameters, were measured on the same leaves usedfor gas exchange experiments. A progressive xeromorphic adaptation in the leaf structure wasobserved with increasing leaf insertion levels. Furthermore,mesophyll cell volume per unit leaf area (Vmes/A) decreasedby 52·6% from the first leaf to the flag leaf. Mesophyllcell area per unit leaf area also decreased, but only by 24·5%.However, nitrogen content per unit mesophyll cell volume increasedby 50·6% from the first leaf to the flag leaf. This increasecould be associated to an observed higher number of chloroplastcross-sections per mm2 of mesophyll cell cross-sectional areain the flag leaf: values of 23000 in the first leaf and 48000in the flag leaf were obtained. Pn per unit leaf area remainedfairly constant at the different insertion levels: values of33·83±0·93 mg dm2 h1 and32·32±1·61 mg dm2 h1 wereobtained for the first leaf and the flag leaf, respectively.Residual conductance, however, decreased by 18·2% fromthe first leaf to the flag leaf. Stomatal conductance increasedby 41·7%. The steadiness in Pn per unit leaf area across the leaf insertionlevels could be mainly accounted for by an opposing effect betweena decrease in Vmes/A and a more closely packed arrangement ofphotosynthetic apparatus. Adaptative significance of structuralchanges with increasing leaf insertion levels and the steadinessin Pn per unit leaf area was studied. Key words: Photosynthesis, structure, wheat 相似文献
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Microswards of white clover (Trifolium repens L.) were grownin controlled environments at 10/7, 18/13 and 26/21 °C day/nighttemperatures. The vertical distribution of leaves of differentages and their rates of 14CO2-uptake in situ were studied. Extending petioles carried the laminae of young leaves throughthe existing foliage. A final position was reached within 1/4to 1/3 of the time between unfolding and death. Newly unfoldedleaves had higher rates of 14CO2-uptake per leaf area than olderones at the same height in the canopy. At higher temperatures,the decrease with age was faster. However, the light-photosynthesisresponse of leaves which were removed from different heightsin the canopy varied much less with leaf age than did the ratesof 14CO2-uptake in situ. The comparison of the rates of 14CO2-uptake in situ with thelight-photosynthesis response curves suggests that young leavesreceive more light than older ones at the same height in thecanopy. This would imply that young white clover leaves havethe ability to reach canopy positions having a favourable lightenvironment. This ability may improve the chances of survivalof white clover in competition with other species. Trifolium repens L., white clover, photosynthesis, canopy, leaf age, 14CO2-uptake, ecotypes, temperature 相似文献
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The pleiotropic effects of three genetically related dwarfinggenes were investigated in near-isogenic lines of wheat. TheNORIN 10 semi-dwarfing alleles, Rht 1 and Rht 2, and the TomThumb allele, Rht 3, were assessed for effects on some vegetativemorphological and physiological characters. The Rht allelesaffected leaf size with a resultant decrease in leaf area ofthe whole plant. Rht 3, which had the most marked effects, reducedleaf area in young plants by as much as 30 per cent. Althoughflag leaf dimensions and stomatal distributions of the flagleaf were altered, the gene had no effect on its area, stomatalconductance or net CO2 exchange rate. Comparisons of Rht andtall plants revealed no differences in the abscisic acid (ABA)levels of either turgid or partially dehydrated leaves. Triticum aestivum L., wheat, dwarfing genes, leaf structure, abscisic acid, stomatal conductance, CO2, exchange, relative growth rate 相似文献
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Bae Gong Young; Nakajima Nobuyoshi; Ishizuka Kozo; Kondo Noriaki 《Plant & cell physiology》1996,37(2):129-134
The rate of evolution of ethylene by tomato plants was rapidlyincreased by O3 fumigation. The time course of the increasein 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activitywas the same as that in the rate of evolution of ethylene, suggestingthat ACC synthase activity might be a rate-limiting step inthe evolution of ethylene that is caused by O3 fumigation. Therate of the O3-induced evolution of ethylene was increased bythe application of ACC to tomato plants, suggesting the involvementof ACC oxidase in the O3-induced evolution of ethylene. Treatmentof plants with tiron inhibited the evolution of ethane, butnot of ethylene. These results indicated that evolution of ethylenein O3-treated tomato plants might result from enzymatic reactionscatalyzed by both ACC synthase and ACC oxidase, but not fromstimulation by O3 of the peroxidation of lipids mediated byfree radicals. Pretreatment of leaves with aminoethoxyvinylglycine (AVG), aninhibitor of ACC synthase, significantly inhibited the evolutionof ethylene that was induced by O3 and concomitantly reducedthe extent of O3-induced visible damage to leaves. Treatmentwith 2,5-norbonadiene, an inhibitor of the action of ethylene,strongly reduced the extent of visible damage caused by O3,even though it did not suppress the evloution of ethylene. Theseresults indicate that ethylene acts on certain metabolic processesto cause visible damage. (Received September 7, 1995; Accepted December 18, 1995) 相似文献
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The Relation Between the Nitrogen Concentration and Photosynthetic Capacity of Potato (Solanum tuberosum L.) Leaves 总被引:1,自引:0,他引:1
Measurements of the rate of light-saturated photosynthesis (Pmax)were made on terminal leaflets of potato plants growing in cropssupplied with 0, 3, 6, 12, 24 and 36 g N m2. Measurementswere made between 100 and 154 d after planting. Two types ofleaf were selectedthe fourth leaf on the second-levelbranch (L4, B1) and the youngest terminal leaflet that was measurable(LYM). Later, the total nitrogen concentration of each leaflet(NL) was measured. A linear regression between Pmax and NL,common to both leaf positions, explained 68.5% of the totalvariation. With L4, B1 leaves there was a significant improvementin the proportion of variation explained when regressions withseparate intercepts and a common slope were fitted to individualfertilizer treatments. These results suggest that an increasingproportion of leaf nitrogen was not associated with the performanceof the photosynthetic system with increasing nitrogen supply.This separation between nitrogen treatments was not as clearfor LYM leaves. Stomatal conductance to transfer of water vapourwas neither influenced by leaf position nor directly by nitrogensupply. Rather conductance declined in parallel with the declinein photosynthetic capacity. Solanum tuberosum, potato, nitrogen, photosynthesis, stomatal conductance, leaf 相似文献
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Baxter R.; Bell S. A.; Sparks T.H.; Ashenden T.W.; Farrar J.F. 《Journal of experimental botany》1995,46(8):917-929
Agrostis capillaris L.5, Festuca vivipara L. and Poaalpina L.were grown in outdoor open-top chambers at either ambient (340 3µmol mol1) or elevated (6804µmol mol1)concentrations of atmospheric carbon dioxide (CO2) for periodsfrom 79189 d. Photosynthetic capacity of source leaves of plants grown atboth ambient and elevated CO2 concentrations was measured atsaturating light and 5% CO2. Dark respiration of leaves wasmeasured using a liquid phase oxygen electrode with the buffersolution in equilibrium with air (21% O2, 0.034% CO2). Photo-syntheticcapacity of P. alpina was reduced by growth at 680 µmolmol1 CO2 by 105 d, and that of F. vivipara was reducedat 65 d and 189 d after CO2 enrichment began, suggesting down-regulationor acclimation. Dark respiration of successive leaf blades ofall three species was unaltered by growth at 680 relative to340 µmol mol1 CO2. In F. vivipara, leaf respirationrate was markedly lower at 189 d than at either 0 d or 65 d,irrespective of growth CO2 concentration. There was a significantlylower total non-structural carbohydrate (TNC) concentrationin the leaf blades and leaf sheaths of A. capillaris grown at680µmol mol1 CO2. TNC of roots of A. capillariswas unaltered by CO2 treatment. TNC concentration was increasedin both leaves and sheaths of P. alpina and F. vivipara after105 d and 65 d growth, respectively. A 4-fold increase in thewater-soluble fraction (fructan) in P. alpina and in all carbohydratefractions in F. vivipara accounted for the increased TNC content. In F. vivipara the relationship between leaf photosyn-theticcapacity and leaf carbohydrate concentration was such that therewas a strong positive correlation between photosynthetic capacityand total leaf N concentration (expressed on a per unit structuraldry weight basis), and total nitrogen concentration of successivemature leaves reduced with time. Multiple regression of leafphotosynthetic capacity upon leaf nitrogen and carbohydrateconcentrations further confirmed that leaf photosynthetic capacitywas mainly determined by leaf N concentration. In P. alpina,leaf photosynthetic capacity was mainly determined by leaf CHOconcentration. Thus there is evidence for down-regulation ofphotosynthetic capacity in P. alpina resulting from increasedcarbohydrate accumulation in source leaves. Leaf dark respiration and total N concentration were positivelycorrelated in P. alpina and F. vivipara. Leaf dark respirationand soluble carbohydrate concentration of source leaves werepositively correlated in A. capillaris. Changes in source leafphotosynthetic capacity and carbohydrate concentration of plantsgrown at ambient or elevated CO2 are discussed in relation toplant growth, nutrient relations and availability of sinks forcarbon. Key words: Elevated CO2, Climate change, grasses, carbohydrate partitioning, photosynthesis, respiration 相似文献