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  • 1
    Electronic Resource
    Electronic Resource
    CHLOROPHYLL DEGRADATION (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 50 (1999), S. 67-95 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Although the loss of green color in senescent leaves and ripening fruits is a spectacular natural phenomenon, research on chlorophyll breakdown has been largely neglected until recently. This review summarizes knowledge about the fate of chlorophyll in degreening tissues that has been gained during the past few years. Structures of end- and intermediary products of degradation as well as the biochemistry of the porphyrin-cleaving reaction have been elucidated. The intracellular localization of the catabolic pathway is particularly important in the regulation of chlorophyll breakdown. None of the genes encoding the related catabolic enzymes has so far been isolated, which makes chlorophyll degradation an area of opportunity for future research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.50.1.67
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf senescence in a non-yellowing mutant of Festuca pratensis: Degradation of carotenoids (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 70 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The loss of pigments was assessed in detached leaves of Festuca pratensis Huds. kept in permanent darkness. Two genotypes, a normal yellowing cultivar Rossa and a non-yellowing mutant Bf 993 were compared with each other. Analysis of individual pigments, chlorophylls. β-carotene, lutein, violaxanthin and neoxanthin was performed using HPLC. In the non-yellowing genotype the high retention of chlorophylls was associated with an equally high retention of total carotenoids. Although the two genotypes differ markedly with regard to the rate of pigment loss, the ratios of yellow to green pigments did not change significantly during dark-induced senescence. At the end of the senescence period β-carotene was retained to a higher degree than the xanthophylls, particularly in the yellowing genotype. In the mutant leaves the ratio of chlorophyll a to b remained nearly constant, whereas in leaves of the normal genotype a preferential retention of chlorophyll b was observed towards the end of the senescence period. It is concluded that the thylakoids of the non-yellowing genotype retain all the principal components of protein-pigment complexes, i.e. chlorophylls, carotenoids and apoproteins. Possible explanations for the stability of these complexes in the mutant are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb04321.x
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  • 3
    Electronic Resource
    Electronic Resource
    Chlorophyll breakdown in senescent leaves: demonstration of Mg-dechelatase activity (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 89 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The action of Mg-dechelatase was brought to light by incubating senescent rape cotyledons or chloroplasts under conditions which prevented the oxidative cleavage of chlorophyll-porphyrin. The accumulation of chlorophyllide and pheophorbide taking place under such conditions was considered as a measure of apparent activities of chlorophyllase and dechelatase, respectively. In excised cotyledons metal chelators such as 2,2′-dipyridyl and o-phenanthroline caused a marked accumulation of pheophorbide a, without affecting the apparent activity of chlorophyllase. Treatment of cotyledons with an inhibitor of cytoplasmic protein synthesis d-2-(4-methyl-2,6-dinitroanilino)-N-methyl-propionamide (d-MDMP) caused a reduced accumulation of pheophorbide a in the presence of dipyridyl, suggesting that the appearance and maintenance of Mg-dechelatase activity in senescent cotyledons requires continuous cytoplasmic protein synthesis. In isolated senescent chloroplasts (gerontoplasts) the cleavage of chlorophyll-porphyrin requires the supplementation with glucose-6-phosphate (Glc6P). Upon the incubation of gerontoplasts in the absence of Glc6P, a conspicuous accumulation of pheophorbide a occurred. Much smaller pools of pheophorbide a were produced when porphyrin cleavage was allowed in the presence of Glc6P. These phenomena were not observed in pre-senescent chloroplasts. In contrast to the apparent Mg-dechelatase activity, chlorophyllase activity did not change in a senescent-specific fashion. The lysis of gerontoplasts by freezing and thawing caused an enhancement of apparent chlorophyllase activity whereas the activity of Mg-dechelatase was lower than in the intact organelles. In the pre-senescent chloroplasts, lysis evoked a small apparent Mg-dechelatase activity, suggesting that in a latent form this enzyme may be present even before the onset of foliar senescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb00165.x
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  • 4
    Electronic Resource
    Electronic Resource
    Leaf senescence in Festuca pratensis: accumulation of lipofuscinlike compounds (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 74 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fluorescent compounds (FCs) with spectral properties comparable to those of lipofuscin-like compounds are present in aqueous methanolic extracts of senescent meadow fescue, Festuca pratensis Huds., leaves. An HPLC system for the separation of FC from other fluorescent materials was developed. The chromatograms suggest that the FC-fraction consists of a large number of chemically related compounds. FCs are accumulated during senescence in leaves of a yellowing genotype, cv. Rossa. In leaves of a non-yellowing genotype, Bf 993, only traces of FCs appear at advanced stages of senescence.FCs are regarded as final products of lipid peroxidation. Since both yellowing and non-yellowing genotypes are competent with regard to the degradation of galactolipids (the potential sources of polyunsaturated fatty acids) as well as regarding lipoxygenase (EC 1.13.11.12; a key enzyme of lipid peroxidation), and since incompentence to degrade chlorophyll is associated with lack of FC accumulation in the mutant genotype, it is hypothesized that the polar FCs present in senescent F. pratensis leaves represent catabolites of chlorophyll.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb04953.x
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  • 5
    Electronic Resource
    Electronic Resource
    Development of an assay for Mg-dechelatase of oilseed rape cotyledons, using chlorophyllin as the substrate (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: Chlorophyllin (Chlin), the Mg-chlorin obtained from chlorophyll (Chl) was employed as substrate of Mg-dechelatase. The release of Mg2+ was associated with a shift of absorption from 644 to 687 nm. Changes of absorption at 687 nm were taken as a measure of Mg-dechelatase activity present in preparations of oilseed rape thylakoids. Absorption changes were correlated linearly with enzyme dose. The pH optimum of Mg release from Chlin was ca 9 with a broad flank down to pH 7. The reaction showed saturation kinetics with an apparent Km value of ca 17 nM. The activity was inhibited in the presence of cysteamine or reduced glutathion. There was no effect of the thiol reagent N-ethyl maleimide. The bulk of dechelatase activity was associated with the chloroplast membranes. The enzyme is partially latent and the appearance of full activity requires the solubilization of thylakoids with detergent. The highest activities were detected in mature green rape cotyledons. During dark-induced senescence the activity declined at roughly the same rate as Chl was lost in the leaf tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00784.x
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  • 6
    Electronic Resource
    Electronic Resource
    Die Funktion proteolytischer Enzyme bei der Proteinaufnahme durchNeurospora crassa (1964)
    Springer
    Naturwissenschaften 51 (1964), S. 489-490 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00633117
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  • 7
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1965)
    Springer
    Naturwissenschaften 52 (1965), S. 484-484 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626258
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  • 8
    Electronic Resource
    Electronic Resource
    Longevity and senescence of needles in Pinus cembra L. (1992)
    Springer
    Trees 6 (1992), S. 156-161 
    Details
    ISSN: 1432-2285
    Keywords: Pinus cembra ; Needle longevity ; Needle senescence ; Nutrient elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Needle development has been investigated in Pinus cembra at several locations in the Grisons. Special attention has been paid to longevity and senescence. Despite large variations from one tree to another, longevity (up to 12 years) appeared to increase with increasing altitude. With increasing age, contents of nutrients such as N, P, K and, to a lesser extent, Mg and S tend to decrease. Photosynthetic activity did not decline with increasing age of short shoots. Senescence begins in mid-August in needles of the oldest age classes. It is associated with the mobilization and withdrawal of large proportions of N, P, K and also Mg and S, but Ca appears to be immobile. The extent of yellowing is irregular in individual trees but needle losses on a large scale are followed by reduced losses in subsequent years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202431
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  • 9
    Electronic Resource
    Electronic Resource
    Catabolism of carotenoids: Involvement of peroxidase? (1982)
    Springer
    Plant cell reports 1 (1982), S. 244-246 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In primary leaves of barley allowed to senesce under natural conditions, carotenoids, like chlorophylls, disappear gradually. Commercial horse-radish peroxidase catalizes the oxidation of lutein to unknown colorless products. This reaction depends on the presence of 2,4 dichlorophenol. It is independent of peroxide but is nullified in the presence of catalase. Preparations of thylakoids from barley chloroplasts show an activity with features comparable to those of horse-radish peroxidase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272629
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  • 10
    Electronic Resource
    Electronic Resource
    Production and release of a chlorophyll catabolite in isolated senescent chloroplasts (1992)
    Springer
    Planta 187 (1992), S. 230-235 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll (breakdown, senescence) ; Chlorophyll catabolite ; Chloroplast (chloroplast senescence) ; Hordeum (chloroplast) ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A non-green catabolite of chlorophyll (Chl) the fluorescent compound FC 2, is produced when intact senescent chloroplasts of barley (Hordeum vulgare L.) are incubated in the presence of ATP. The origin of FC 2 has now been demonstrated by employing senescent chloroplasts containing Chl 14C-labelled in the pyrrole-rings: upon incubation in the presence of ATP, 14C-labelled FC 2 is generated. The production of FC 2 requires the hydrolysis of ATP as demonstrated by the failure of the β, γ-imido analogue to support the reaction. Adenosine triphosphate can partially be replaced by UTP but GTP and CTP, as well as ADP and AMP, are ineffective. The system responsible for FC 2 production can also be fueled with glucose-6-phosphate, fructose-6-phosphate and glucose-1-phosphate; other sugar-phosphates including glyceraldehyde-3-phosphate have no effect. Adenosine triphosphate is also required for the release of FC 2 from chloroplasts. When chloroplasts are incubated in the presence of UTP or hexose-monophosphates which support the generation of FC 2 within the organelles, the catabolite is not released. It is concluded that the envelope of senescent chloroplasts is equipped with translocators for the cytosolic compounds which provide the metabolic energy and cofactors required for the action of the catalyst(s) responsible for the oxidative cleavage of Chl-porphyrin and possibly also for the dismantling of Chl-protein complexes. Moreover, a translocator may be involved in the release of the primary catabolites of Chl from chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201944
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