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  • 1
    Electronic Resource
    Electronic Resource
    Early degradation of photosynthetic membranes in carob and sunflower cotyledons (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 96 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The assimilatory activity of cotyledons can play an essential role in the survival of seedlings with a slow and delayed development of primary leaves. Changes in the photosynthetic activity of the cotyledon, from the onset of greening through senescence, were studied in two such plants, carob and sunflower, in order to determine its efficiency and duration, also in connection with the achievement of assimilatory autonomy by the plantlet. Chlorophyll analyses showed that the cotyledon's chloroplasts reached maximal greening in plantlets with a pair of expanded leaves. In contrast, the cotyledon's photosynthetic activity, measured as the rate of oxygen release, started to decrease early, before expansion of primary leaves. The decrease was due to the inactivation of a number of photosystem II (PSII) units, as revealed by immunodetection of breackdown products of the reaction centre's D1 and D2 thylakoid proteins. No signals of PSII alteration were noticed in the primary leaf chloroplasts that differentiated under the same environmental conditions. The damage to the cotyledon PSII, occurring in a non-photoinhibitory situation, might be due to a slower rate of turnover of D1 polypeptide than in the leaf thylakoids. The differential turnover of this protein in cotyledons and in leaves might represent an organ-specific regulation of the photosynthetic activity. The peculiarity of the cotyledon thylakoids make these organs useful objects for studying the metabolic cycle of both D1 and D2 proteins in vivo, under non-photoinhibiting conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00466.x
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  • 2
    Electronic Resource
    Electronic Resource
    Expression of chloroplastic and cytosolic glutamine synthetase in barley leaves after cold-sensitive blocking of β-carotene synthesis by amitrole or mutation (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 3-Amino- 1,2,4-triazole (amitrole) provided to germinating barley at 20°C in the light led to bleached seedling leaves and photodynamic destruction of chloroplast structure, whereas normal greening and chloroplast ultrastructure was obtained when the seedlings developed in the presence of amitrole in the light at 30°C. Mass spectrometric analysis of the extractable herbicide demonstrated the same content of amitrole in leaves developed at 20 and 30°C. A very similar temperature-sensitive syndrome is characteristic for the nuclear gene mutant ligrina-o34 in barley. Amitrole and the mutation were shown to inhibit the cyclization of lycopene, leading to severe deficiencies in β-carotene and its xanthophyll derivative lutein. Besides accumulation of lycopene, also its precursors phytoene, phytofluene and ξ-carotene accumulated. Inhibition of carotenoid biosynthesis by amitrole and the mutation at 20°C in the light led to a strong reduction of both transcript and protein levels for chloroplastic glutamine synthetase (GS2) while transcript amount and protein of the cytosolic isoenzyme (GS1) were unaffected. At 30°C increased levels of mRNA for the chloroplastic isoform GS2 were observed in wild type, mutant and amitrole-treated seedlings, but protein levels remained unchanged. Turnover rates of the GS2 protein were the same at 20 and 30°C. This extensive translational control of chloroplastic GS2 synthesis was also observed in a heat shock experiment, which revealed transiently increased mRNA levels for chloroplastic GS2 but unchanged protein levels.Permissive synthesis of β-carotene and chloroplastic glutamine synthetase (GS2) at 30°C in the presence of amitrole or the tigrina-o34 mutation might be due to two alternative pathways of ionone ring formation using either lycopene or neurosporene as substrates for cyclization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00965.x
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  • 3
    Electronic Resource
    Electronic Resource
    Cotyledonal chloroplasts in the hypogeal seeds of clementine (1987)
    Springer
    Planta 170 (1987), S. 300-307 
    Details
    ISSN: 1432-2048
    Keywords: Chloroembryophyte ; Chloroplast (differential development) ; Citrus ; Embryo (chloroplasts) ; Seed germination ; Thylakoid (polypeptides)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clementine (Citrus nobilisxCitrus aurantium amara pumila) is a chloroembryophyte with green quiescent embryos and hypogeal germination. The cotyledonal chloroplasts have been studied during germination in the dark and under two different irradiances 120 and 240 μmol·m-2·s-1 throughout a period of three weeks. The plastids of the outer adaxial and inner regions develop differently. In the light, the former differentiate a photosynthetically active thylakoid system with an ultrastructural organization and a polypeptide composition resembling that of leaf chloroplasts. The “inner” chloroplasts maintain an organization reminiscent of chloroplasts of the quiescent embryo and never get beyond the photosynthesis/respiration compensation point; their differentiation pattern appears essentially the same under the two different irradiances. These observations and the germination in the dark indicate that the above differentiation is not strictly photodependent. The greening ability of the cotyledons provides, on occasion, an additional photosynthetic supply to this plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395020
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  • 4
    Electronic Resource
    Electronic Resource
    Structural and biochemical aspects of peach fruit abscission (Prunus persica L. Batsch) (1985)
    Springer
    Planta 164 (1985), S. 1-11 
    Details
    ISSN: 1432-2048
    Keywords: Abscission (fruit) ; Cellulase ; Fruit abscission ; Polygalacturonase ; Prunus (abscission)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physiological drop of immature fruits was studied in relation to the activation of the abscission zone located between the fruit and the receptacle. Light- and electron-microscopy observations demonstrated that this zone consisted of two types of parenchymatous cells: in the distal region, closer to the fruit, were groups of small thick-walled cells with few intercellular spaces; in the proximal region, closer to the pedicel, the stillgrouped cells were larger, polyphenolic-rich, and thick-walled but with many wide intercellular spaces. Separation of the fruit occurred by dissolution of the middle lamella of the cells of this zone followed by an increase in the size of the intercellular spaces. Lysis of the middle lamella began at the corners of the cells and spread from there across the entire wall surface. Structural changes were paralleled by an increase in soluble proteins, endo-cellulase and exo-polygalacturonase activity. Isoelectric focusing indicated that both enzymes were present as isoenzymes whose patterns were affected by embryoctomy and 2-chloroethylphosphonic acid treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391019
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  • 5
    Electronic Resource
    Electronic Resource
    A novel E-type endo-β-1,4-glucanase with a putative cellulose-binding domain is highly expressed in ripening strawberry fruits (1999)
    Springer
    Plant molecular biology 40 (1999), S. 323-332 
    Details
    ISSN: 1573-5028
    Keywords: cellulose-binding domain ; endo-β-1,4-glucanase ; fruit ripening ; strawberry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two full-length cDNA clones (faEG1 and faEG3, respectively) have been isolated by screening a cDNA library representing transcripts from red strawberry fruits. Southern blot analysis of genomic DNA suggests that the strawberry endo-β-1,4-glucanases (EGases) are encoded by a multigene family. The cognate genes are predominantly expressed during the ripening process proper, although, in the case of faEG3, some expression has also been observed in large green fruits and, at low amounts, in young vegetative green tissues. In agreement with other ripening-related genes in strawberry, also the expression of faEG1 and faEG3 is down-regulated by treatment with an auxin analogue (1-naphthaleneacetic acid, NAA). Differences in temporal expression of the two EGase genes in fruits are not accompanied by differences in spatial expression. The pattern of expression and the sequence characteristics of the two polypeptides suggest that the two strawberry EGases operate in a synergistic and coordinate manner. The protein encoded by faEG1 looks like one of the usual higher-plant EGases (average molecular mass of 54 kDa), while the protein encoded by faEG3 has a greater deduced molecular mass (about 68 kDa) due to the presence of an extra peptide of about 130 amino acids at the C-terminus. Such unusual peptide shows some features also found in microbial cellulases and contains a putative cellulose-binding domain. We propose that the faEG3-encoded EGase might especially hydrolyse the xyloglucans coating the cellulose microfibrils, thus rendering the cell wall more susceptible to the subsequent hydrolytic activity of the faEG1-encoded EGase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006299821980
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  • 6
    Electronic Resource
    Electronic Resource
    A cDNA sequence coding for glutamine synthetase in Ordeum vulgare L. (1990)
    Springer
    Plant molecular biology 15 (1990), S. 161-163 
    Details
    ISSN: 1573-5028
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017735
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  • 7
    Electronic Resource
    Electronic Resource
    Differential ethylene-inducible expression of cellulase in pepper plants (1995)
    Springer
    Plant molecular biology 29 (1995), S. 735-747 
    Details
    ISSN: 1573-5028
    Keywords: Capsicum annuum ; endo-β-(1,4)-glucanase ; ethylene ; leaf abscission ; nucleotide sequence ; ripening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ethylene promotes the abscission of leaves and the ripening of fruits in pepper plants, and in both events an increase in cellulase activity is observed. However, two enzyme isoforms (pI 7.2 and 8.5, respectively) are differentially involved in the two physiological phenomena. The pI 8.5 form has been purified from ripe fruits. It is a glycoprotein with an apparent molecular mass of 54 kDa. Two short peptides were sequenced and a very high homology to a tomato cellulase was observed. Polyclonal antibodies, raised against the purified enzyme, have allowed us to demonstrate that the observed ethylene-induced increase in cellulase activity is paralleled by de novo synthesis of protein. Three cDNAs (CX1, CX2 and CX3), encoding different cellulases, were obtained and characterized and their expression investigated. Accumulation of all three mRNAs is induced by ethylene treatment, though to different levels. CX1 is mainly expressed in ripe fruits while CX2 is especially found in abscission zones. CX3 accumulates at very low levels in activated abscission zones. Comparisons with other known cellulases demonstrate clear heterogeneity within the higher plant cellulases. Differences in ethylene inducibility and molecular structure suggest different physiological roles for cellulase in pepper plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041164
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of ppEG1, a member of a multigene family which encodes endo-β-1,4-glucanase in peach (1997)
    Springer
    Plant molecular biology 34 (1997), S. 791-802 
    Details
    ISSN: 1573-5028
    Keywords: abscission ; endo-β-1,4-glucanase ; ethylene ; promoter ; Prunus persica ; transgenic tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three cDNA clones (pCel10, pCel20 and pCel30), each encoding different endo-β-1,4-glucanases in peach, were obtained by RT-PCR and their expression investigated by northern analysis during leaf and fruit abscission and during fruit development. This analysis allowed the detection of only the pCel10-related mRNA. A 2.2 kb transcript accumulated in ethylene activated abscission zones of leaves and fruits, and ppEG1 (Prunus persica endoglucanase 1) the gene coding for pCel10, was isolated and characterized. A cDNA (termed pCel1), containing the entire open reading frame of ppEG1, was obtained and its sequence used to define the structure of the gene and the exon/intron boundaries. ppEG1 consists of 7 exons and encodes a 497 amino acid polypeptide including a putative signal peptide at the N-terminus. The similarity of this peach endo-β-1,4-glucanase (EGase, EC 3.2.1.4) is high (76.3%) with the ripening avocado and low (47.3%) with the bean abscission EGase. A 1639 bp region at the 5′ of the transcription start site shows regulatory functions in transgenic tobacco plants, as judged by its ability to drive GUS expression in cell separation-related events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005884429760
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