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  • 1
    ISSN: 1432-2048
    Keywords: d-Amino acid ; 1-Aminocyclopropane-1-carboxylic acid ; α-Aminoisobutyric acid ; Ethylene synthesis ; 1-(Malonylamino)cyclopropane-1-carboxylic acid ; α-(Malonylamino)isobutyric ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1-Aminocyclopropane-1-carboxylic acid (ACC) is known to be converted to ethylene and conjugated into N-malonyl-ACC in plant tissues. When α-amino[1-14C]isobutyric acid (AIB), a structural analog of ACC, was administered to mungbean (Vigna radiata L.) hypocotyl segments, it was metabolized to 14CO2 and conjugated to N-malonyl-AIB (MAIB). α-Aminoisobutyric acid inhibited the conversion of ACC to ethylene and also inhibited, to a lesser extent, N-malonylation of ACC and d-amino acids. Although the malonylation of AIB was strongly inhibited by ACC as well as by d-amino acids, the metabolism of AIB to CO2 was inhibited only by ACC but not by d-amino acids. Inhibitors of ACC conversion to ethylene such as anaerobiosis, 2,4-dinitrophenol and Co2+, similarly inhibited the conversion of AIB to CO2. These results indicate that the malonyalation of AIB to MAIB is intimately related to the malonylation of ACC and d-amino acids, whereas oxidative decarboxylation of AIB is related to the oxidative degradation of ACC to ethylene.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: 1-Aminocyclopropane-1-carboxylate oxidase ; Ethylene ; Gene expression ; Hypocotyl excision ; Vigna ; Wounding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By screening a mung bean (Vigna radiata L.) hypocotyl cDNA library using a combination of apple (pAE12) and tomato (pTOM13) 1-aminocyclopropane1-carboxylate (ACC)-oxidase cDNAs as probes, putative ACC-oxidase clones were isolated. Based on restriction-enzyme map and DNA-sequencing analyses, they can be divided into two homology classes, represented by pVR-ACO1 and pVR-ACO2. While pVR-ACO1 and pVR-ACO2 exhibit close homology in their coding regions, their 3′-noncoding regions are divergent. pVR-ACO1 is a 1312-bp full-length clone and contains a single open reading frame encoding 317 amino acids (MW = 35.8 kDa), while pVR-ACO2 is 1172 bp long and is a partial cDNA clone encoding 308 amino acids. These two deduced amino-acid sequences share 83% identity, and display considerable sequence conservation (73–86%) to other ACC oxidases from various plant species. Northern blot analyses of RNAs isolated from hypocotyl, leaf, and stem tissues using gene-specific probes indicate that the pVR-ACO1 transcript is present in all parts of the seedling and that the expression in hypocotyls is further increased following excision. The maximum induction of ACC-oxidase transcripts occurred at about 6 h after excision, while the maximum enzyme activity was observed at 24 h. When excised hypocotyls were treated with ethylene a further enhanced level of transcripts was observed. Aminooxyacetic acid, an inhibitor of ACC-synthase activity, and 2,5-norbornadiene, an inhibitor of ethylene action, suppressed the wound-induced accumulation of ACC-oxidase mRNA, while an addition of ethylene in these tissues restored the accumulation of ACC-oxidase mRNA. These results indicate that the wound-induced expression of ACC-oxidase transcripts is mediated through wound-induced ethylene. Furthermore, when intact mung-bean seedlings were treated with exogenous ethylene, a marked increase in the level of ACC-oxidase mRNA was observed. Together, these results indicate that ethylene plays a key role in activating the expression of the ACC-oxidase gene in both intact and excised mung-bean hypocotyls.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: 1-Aminocyclopropane-1-carboxylic acid ; Carbon dioxide and C2H4 production ; Ethylene production ; Light and C2H4 production ; Nicotiana Fellowship ; Oryza
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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 CO2 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 CO2 treatment, indicating that dark treatment or CO2exerted 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 CO2. Similar results were obtained with tobacco leaf discs. The concentrations of CO2 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 CO2 or light in detached leaves of both rice and tobacco was rapid and fully reversible, indicating that CO2 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 CO2, which directly modulates the activity of the enzyme converting ACC to ethylene.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2048
    Keywords: 1-Amninocyclopropane-1-carboxylate synthase ; cDNA ; Ethylene synthesis ; Fruit ripening ; Gene expression ; Malus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1-Aminocyclopropane-1-carboxylate (ACC) synthase (EC 4.4.1.14) purified from apple (Malus sylvestris Mill.) fruit was subjected to trypsin digestion. Following separation by reversed-phase high-pressure liquid chromatography, ten tryptic peptides were sequenced. Based on the sequences of three tryptic peptides, three sets of mixed oligonucleotide probes were synthesized and used to screen a plasmid cDNA library prepared from poly(A)+ RNA of ripe apple fruit. A 1.5-kb (kilobase) cDNA clone which hybridized to all three probes were isolated. The clone contained an open reading frame of 1214 base pairs (bp) encoding a sequence of 404 amino acids. While the polyadenine tail at the 3′-end was intact, it lacked a portion of sequence at the 5′-end. Using the RNA-based polymerase chain reaction, an additional sequence of 148 bp was obtained at the 5′-end. Thus, 1362 bp were sequenced and they encode 454 amino acids. The deduced amino-acid sequence contained peptide sequences corresponding to all ten tryptic fragments, confirming the identity of the cDNA clone. Comparison of the deduced amino-acid sequence between ACC synthase from apple fruit and those from tomato (Lycopersicon esculentum Mill.) and winter squash (Cucurbita maxima Duch.) fruits demonstrated the presence of seven highly conserved regions, including the previously identified region for the active site. The size of the translation product of ACC-synthase mRNA was similar to that of the mature protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), indicating that apple ACC-synthase undergoes only minor, if any, post-translational proteolytic processing. Analysis of ACC-synthase mRNA by in-vitro translation-immunoprecipitation, and by Northern blotting indicates that the ACC-synthase mRNA was undetectable in unripe fruit, but was accumulated massively during the ripening proccess. These data demonstrate that the expression of the ACC-synthase gene is developmentally regulated.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2048
    Keywords: 1-Aminocyclopropane-1-carboxylate oxidase ; Ethylene ; Gene expression ; Hypocotyl excision ; Vigna ; Wounding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By screening a mung bean (Vigna radiata L.) hypocotyl cDNA library using a combination of apple (pAE12) and tomato (pTOM13) 1-aminocyclopropane1-carboxylate (ACC)-oxidase cDNAs as probes, putative ACC-oxidase clones were isolated. Based on restriction-enzyme map and DNA-sequencing analyses, they can be divided into two homology classes, represented by pVR-ACO1 and pVR-ACO2. While pVR-ACO1 and pVR-ACO2 exhibit close homology in their coding regions, their 3′-noncoding regions are divergent. pVR-ACO1 is a 1312-bp full-length clone and contains a single open reading frame encoding 317 amino acids (MW = 35.8 kDa), while pVR-ACO2 is 1172 bp long and is a partial cDNA clone encoding 308 amino acids. These two deduced amino-acid sequences share 83% identity, and display considerable sequence conservation (73–86%) to other ACC oxidases from various plant species. Northern blot analyses of RNAs isolated from hypocotyl, leaf, and stem tissues using gene-specific probes indicate that the pVR-ACO1 transcript is present in all parts of the seedling and that the expression in hypocotyls is further increased following excision. The maximum induction of ACC-oxidase transcripts occurred at about 6 h after excision, while the maximum enzyme activity was observed at 24 h. When excised hypocotyls were treated with ethylene a further enhanced level of transcripts was observed. Aminooxyacetic acid, an inhibitor of ACC-synthase activity, and 2,5-norbornadiene, an inhibitor of ethylene action, suppressed the wound-induced accumulation of ACC-oxidase mRNA, while an addition of ethylene in these tissues restored the accumulation of ACC-oxidase mRNA. These results indicate that the wound-induced expression of ACC-oxidase transcripts is mediated through wound-induced ethylene. Furthermore, when intact mung-bean seedlings were treated with exogenous ethylene, a marked increase in the level of ACC-oxidase mRNA was observed. Together, these results indicate that ethylene plays a key role in activating the expression of the ACC-oxidase gene in both intact and excised mung-bean hypocotyls.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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