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.     

Properties and Partial Purification of 1-Aminocyclopropane-1-carboxylate Synthase

We studied the regulation of 1-aminocyclopropane-1-carboxylate (ACC) synthase activity in tomato (Lycopersicon esculentum Mill.) fruit tissue and attempted the purification of this enzyme. The increase of ACC synthase activity in wounded tomato pericarp was inhibited by cordycepin and cycloheximide. Density labeling studies showed a 0.75% increase in the buoyant density of ACC synthase isolated from tomato pericarp tissue that had been incubated on ²H₂O as compared to ACC synthase from H₂O-treated tissue. These data are consistent with the hypothesis that ACC synthase is synthesized de novo following wounding of tomato pericarp tissue. SDS-gel electrophoresis and fluorography showed that the pattern of incorporation of l-[³⁵S]methionine into protein changed with time after wounding of the tissue. Radioactive protein bands that were not detected 1 hour after wounding, became apparent 2 to 3 hours after wounding.     

Regulation of Secondary Metabolite Biosynthesis: Catabolite Repression of Phenoxazinone Synthase and Actinomycin Formation by Glucose

Synthesis of the secondary metabolite, actinomycin, and the enzyme, phenoxazinone synthase, involved in the biosynthesis of the antibiotic, were shown to be under severe catabolite repression by glucose. Of a variety of hexoses and carbon compounds examined, glucose, and to a lesser extent, mannose, proved to be the most repressive for enzyme synthesis. The repression by glucose was most evident before production of the antibiotic. In a chemically defined medium suitable for actinomycin production, synthesis of phenoxazinone synthase began at the time the glucose (0.1%) supply was depleted. Soon after, antibiotic synthesis was initiated. Galactose, the major carbon source for growth and antibiotic synthesis, was not utilized until the glucose was consumed. Generally, carbon compounds which supported a rapid rate of growth were most effective in producing catabolite repression.     

Immunochemical Difference of Wound-Induced 1-Aminocyclopropane-1-carboxylate Synthase from the Auxin-Induced Enzyme

Immunochemical cross-reactivity of wound- and auxin-induced1-aminocyclopropane-1-carboxylate (ACC) synthase was examinedwith the antibody against wound-induced ACC synthase purifiedfrom mesocarp of winter squash (Cucurbita maxima Duch.). Theantibody recognized ACC synthase from wounded hypocotyls ofwinter squash and from wounded pericarp of tomato fruits, butnot the enzyme from IAA-treated hypocotyls of winter squash,tomato and mung bean. These results indicate that the primarystructure of the wound-induced enzyme is different from thatof the auxin-induced enzyme in the same species, and impliesthat there are two different genes for ACC synthase, one forwound induction and the other for auxin induction. (Received June 14, 1988; Accepted July 20, 1988)     

Apple 1-Aminocyclopropane-1-Carboxylic Acid Synthase Genes, MdACS1 and MdACS3a, are Expressed in Different Systems of Ethylene Biosynthesis

1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is one of the key regulatory enzymes involved in the synthesis of ethylene. Climacteric fruit ripening is accompanied by increased ethylene production, in which ethylene biosynthesis is changed from system 1 to system 2. In apple, at least four members of the ACS gene family have been identified, two of which, MdACS1 and MdACS3a, have been studied extensively due to their specific expression in fruit tissue. However, the regulatory role of MdACS1 and MdACS3a in the ethylene biosynthesis system is unknown. Here we addressed this issue by investigating ACS expression in ripening apple fruits. Expression analysis in ‘Golden Delicious’ and ‘Red Fuji’ fruits, in combination with treatments of 1-MCP (1-methylcyclopropene, an ethylene inhibitor) and Ethephon (an ethylene releaser) has demonstrated that MdACS3a and MdACS1operate in system 1 and system 2 ethylene biosynthesis, respectively.     

1-Aminocyclopropane-1-Carboxylate Oxidase Activity Limits Ethylene Biosynthesis in Rumex palustris during Submergence

Submergence strongly stimulates petiole elongation in Rumex palustris, and ethylene accumulation initiates and maintains this response in submerged tissues. cDNAs from R. palustris corresponding to a 1-aminocyclopropane-1-carboxylate (ACC) oxidase gene (RP-ACO1) were isolated from elongating petioles and used to study the expression of the corresponding gene. An increase in RP-ACO1 messenger was observed in the petioles and lamina of elongating leaves 2 h after the start of submergence. ACC oxidase enzyme activity was measured in homogenates of R. palustris shoots, and a relevant increase was observed within 12 h under water with a maximum after 24 h. We have shown previously that the ethylene production rate of submerged shoots does not increase significantly during the first 24 h of submergence (L.A.C.J. Voesenek, M. Banga, R. H. Thier, C.M. Mudde, F.M. Harren, G.W.M. Barendse, C.W.P.M. Blom [1993] Plant Physiol 103: 783-791), suggesting that under these conditions ACC oxidase activity is inhibited in vivo. We found evidence that this inhibition is caused by a reduction of oxygen levels. We hypothesize that an increased ACC oxidase enzyme concentration counterbalances the reduced enzyme activity caused by low oxygen concentration during submergence, thus sustaining ethylene production under these conditions. Therefore, ethylene biosynthesis seems to be limited at the level of ACC oxidase activity rather than by ACC synthase in R. palustris during submergence.     

Wound-Induced Ethylene Production and 1-Aminocyclopropane-1-carboxylic Acid Synthase in Mesocarp Tissue of Winter Squash Fruit

Discs (9 mm in diameter and 2 mm in thickness) sliced from mesocarpof winter squash fruit (Cucurbita maxima Duch.) upon incubationat 24°C produced ethylene at an increasing rate after alag period of 3 h. 1-Aminocydopropane-l-carboxylic acid (ACC)synthase activity also increased at a rapid rate after lag periodof less than 3 h, reaching a peak 14 h after incubation andthen declining sharply. The rise in ACC synthase activity precededa rapid increase in ACC formation and ethylene production. Inductionof ACC synthase by wounding in sliced discs was strongly suppressedby the application of cycloheximide, actinomycin D and cordycepin,suggesting that the rise in ACC synthase activity may resultfrom de novo synthesis of protein. ACC synthase extracted from wounded tissue of winter squashmesocarp required pyridoxal phosphate for its maximum activity.The optimum pH of the reaction was 8.5. Km value for S-adenosylmethioninewas 120 µM. The reaction was markedly inhibited by aminoethoxyvinylglycinewith Ki value being 2.7 µM. (Received March 23, 1983; Accepted May 23, 1983)     

Free Radical-mediated Formation of Ethylene from 1-Aminocyclopropane-1-carboxylic Acid: A Spin-frap Study

The ability of free radicals to convert l-aminocyclopropane-l-carboxylicacid (ACC) to ethylene under strictly chemical conditions hasbeen investigated using the aerobic xanthine/xanthine oxidasereaction and the Fenton reaction. Ethylene is formed when 1mM ACC is added to either of these reactions. Ethylene productionby the xanthine/xanthine oxidase system can be stimulated byH₂O₂ and inhibited by both catalase and superoxide dismutase,suggesting that the hydroxyl radical (OH?) formed by the Haber-Weissreaction is reacting with ACC to form ethylene. Ethylene productionfrom ACC by the Fenton reagent, which also produces OH?, showsa strong dependence upon H₂O₂. Involvement of the OH? radicalwas confirmed by spin-trap studies using 5,5-dimethyl-l-pyrroline-l-oxide(DMPO). Only the hydroxyl adduct of DMPO was detectable in boththe xanthine/xanthine oxidase reaction and the Fenton reaction.When ACC was added to the Fenton reaction, an additional adductof DMPO was detectable, which, on the basis of its hyperfinesplitting constants, can be tentatively identified as the DMPOadduct of a carbon-centered free radical. The data are consistentwith the view that formation of ethylene from ACC entails attackby OH? and the resultant formation of a carbon-centered radical,possibly of ACC. The chemical conversion of ACC to ethyleneis less efficient than that characteristic of senescing tissues,in which the reaction is enzymatically mediated. (Received October 1, 1981; Accepted November 17, 1981)     

ACC脱氨酶的应用研究进展与评述

ACC脱氨酶是一种有效降低逆境乙烯含量的外源促生物质,该酶在干旱、盐胁迫及重金属污染等逆境条件下能显著提高农作物的抗逆性和增加产量,深入挖掘ACC脱氨酶的应用价值对农业可持续发展具有重要的意义.该文综述了ACC脱氨酶的作用机制及酶活性的影响因素,并重点论述了ACC脱氨酶在提高作物抗逆性及产量和转基因技术等方面应用研究进展.分析了关于拓展ACC脱氨酶取材和应用范围,量化含ACC脱氨酶的根际微生物定殖能力等问题,并展望了 ACC脱氨酶在植物修复领域的应用以及建立ACC脱氨酶转基因技术体系等方面的研究前景和意义.     

Molecular Size of Wound-Induced 1-Aminocyclopropane-1-carboxylate Synthase from Cucurbita maxima Duch. and Change of Translatable mRNA of the Enzyme after Wounding

Wound-induced 1-aminocyclopropane-1-carboxylate (ACC) synthasewas purified by an immunoaffinity column from wounded mesocarpof winter squash (Cucurbita maxima Duch. cv. Ebisu) fruit, anda specific antibody was raised in rabbit. Translatable mRNAcoding for ACC synthase was barely detectable in fresh tissuebut clearly increased after wounding. The apparent molecularsize of the purified enzyme as estimated by SDS-polyacrylamidegel electrophoresis (PAGE) was about 50 kDa. However, SDS-PAGEfluorograms of in vitro translation product of ACC synthasemRNA and the in vivo labeled enzyme as well as Western blotanalysis showed that the subunit size of the enzyme was 58 kDa.The enzyme was partially degraded or processed to a 50 kDa peptideboth in vivo and in vitro. (Received December 19, 1987; Accepted June 13, 1988)     

Identification of the Reactive Sulfhydryl Group of 1-Aminocyclopropane-1-carboxylate Deaminase

1-Aminocyclopropane-1-carboxylate (ACC) deaminase, a pyridoxal phosphate enzyme that catalyzes cyclopropanring-opening and deamination of ACC, formed a quinoid intermediate with D-alanine, as shown by the appearance of a 510-nm absorption band. The presence of D-alanine also stimulated the inactivation of ACC deaminase with iodoacetamide.The increase of absorbance at 510 nm and the stimulation of the enzyme inactivation were temperature-dependent with a critical point at around 20°C, indicating a conformational change of the enzyme. To identify a reactive thiol group, this stimulated inactivation and an iodoacetantide derivative, N-(iodoacetamidoethyl)-1-aminonaphthalene-5-sulfonic acid were used. The residue that was modified by the specific reagent was monitored by absorbance at 350 nm through the digestion by lysylendopeptidase and the fractionation of peptides, and it was located at Cys-162 near the midpoint of the whole peptide chain of the ACC deaminase.     

Differential Expression of 1-Aminocyclopropane-1-carboxylate Synthase and Oxidase Gene Family in Micro-Tom Tomato Leaves and Roots Under Short Daily UV Radiation

Journal of Plant Growth Regulation - Few studies focussed on the effects of UV radiation on ethylene (ET) production, thus little is known about the changes in the expression of the ET biosynthetic...     

Induction of 1-Aminocyclopropane-1-carboxylic Acid Synthase in Wounded Mesocarp Tissue of Winter Squash Fruit and the Effects of Ethylene

1-Aminocyclopropane-1-carboxylic acid (ACC) synthase activityincreased rapidly after wounding of mesocarp tissue of wintersquash fruit (Cucurbita maxima Duch.) and reached a peak at16 h after excision and then declined sharply. The rise in ACCsynthase activity was followed by increases in the endogenousACC content and the rate of ethylene production. The activityof ethylene forming enzyme (EFE) also increased rapidly in theexcised discs of mesocarp of winter squash fruit. ACC synthase activity was strongly inhibited by aminoethoxyvinylglycinewith a Ki value of 2.1 µM. Michaelis-Menten constant ofACC synthase for S-adenosylmethionine was 13.3 µM. Ethylene suppressed the induction of ACC synthase in the woundedmesocarp tissue. The suppression by ethylene increased withthe increasing concentrations of applied ethylene and the maximumeffect was obtained at about 100 µl 1^–1 ethylene,at which point the induction was suppressed by 54%. Ethylenedid not inhibit ACC synthase activity, nor did it suppress theinduction of EFE, but rather it slightly enhanced the latter. (Received August 24, 1984; Accepted October 29, 1984)