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  • Chloroplast biogenesis  (2)
  • Chlorophyll-protein complexes  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Fate of the porphyrin cofactors during the light-dependent turnover of catalase and of the photosystem II reaction-center protein D1 in mature rye leaves (1996)
    Springer
    Planta 198 (1996), S. 413-422 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll-protein complexes ; Gabaculine ; Heme ; Light stress ; Photoinhibition ; Secale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The apoprotein of the enzyme catalase (EC 1.11.1.6) was shown to exhibit a light-dependent turnover in leaves. Present results indicate that photoinactivation of the enzyme was not accompanied by a synchronous destruction and new synthesis of its heme moiety. In rye (Secale cereale L.) leaves the catalase content was not depleted in light when porphyrin synthesis was inhibited by gabaculine. Photoinactivation of purified bovine liver or rye leaf catalase in vitro was not accompanied by concomitant damage to the heme groups. Both the incorporation of δ-[3H]aminolevulinic acid ([3H]ALA) into catalase-heme and its apparent turnover increased with irradiance. However, the apparent half-life of the catalase-heme was much longer than that of its apoprotein. It is probable that not only degradation but also an exchange with the free heme pool contributed to the apparent turnover of radioactivity of the catalase-heme. Part of the chlorophyll (Chl) associated with photosystem II (PS II) had a preferential light-induced turnover, and repair of PS II appeared to require new Chl synthesis also in mature green rye leaves. The activity of PS II, indicated by the ratio of variable to maximal fluorescence (Fv/Fm), rapidly declined in the presence of gabaculine in light and the reaction-center proteins D1 and D2 were depleted. When segments of mature green rye leaves were labeled with [3H]ALA and incorporation into Chl-protein complexes analysed after electrophoretic separation in the presence of Deriphat, the highest radioactivity was observed in the core complex of PS II, while PS I and the light-harvesting complex of PS II (LHC II) were unlabeled. In greening etiolated leaves highest incorporation was observed in LHC II. Both the incorporation of [3H]ALA into the PS II core complex of green rye leaves and its turnover increased with irradiance. However, the apparent half-life of the PS II-bound labeled porphyrin compounds (mainly Chl) was considerably longer than that of the reaction-center protein D1 under identical conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620058
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  • 2
    Electronic Resource
    Electronic Resource
    Capacity for chlorophyll synthesis in heat-bleached 70S ribosome-deficient rye leaves (1977)
    Springer
    Planta 135 (1977), S. 83-88 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Chloroplast biogenesis ; High-temperature sensitivity ; Plastid ribosomes ; Ribosomes ; Secale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The leaves of young rye plants (Secale cereale L.) grown at 32° were deficient in chlorophyll and in chloroplastic rRNA as compared to those grown at 22°, which developed normally. Both chlorophyll accumulation and the formation of plastidic rRNA were largely restored at 32° when the plants were transfered several times for 1 h per day to 22°. In the chlorotic 32°-grown rye leaves the in vivo activity of δ-aminolevulinate synthetase was very low. Aminolevulinate dehydratase however, exhibited high activity in extracts from 32°-grown leaves and was localized in the plastid fraction isolated from the chlorotic leaf tissue. After application of δ-aminolevulinic acid to chlorotic parts of leaves growing at 32°, protochlorophyll(ide) was formed and accumulated in the dark. In the light, the protochlorophyll(ide) was photooxidized at 32°. The results suggest a cytoplasmic site of synthesis for the series of enzymes converting δ-aminolevulinate to protochlorophyll(ide). It is concluded that an inhibition of δ-aminolevulinate synthetase and the photooxidation of protochlorophyll(ide) or chlorophyll are responsible for the chlorosis of the leaves at 32°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387980
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative analysis of the action of cytokinin and light on the formation of ribulosebisphosphate carboxylase and plastid biogenesis (1978)
    Springer
    Planta 142 (1978), S. 75-82 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast biogenesis ; Cytokinins ; Enzyme development ; Photoregulation ; Ribulose-1,5-bisphosphate carboxylase ; Secale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of cytokinin in plastid biogenesis was investigated in etiolated rye leaves (Secale cereale L.) and compared with the effect of white light. Cytokinin deficiency of the leaves was induced by early excision of the seedling roots and reversed by the application of kinetin. The cytokinin supply had a much greater influence on plastid biogenesis than on leaf growth in general. The activities of several chloroplastic enzymes were increased 200%–400% after kinetin treatment of cytokinin-depleted leaves. The activity of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and the amount of fraction-I protein even showed a sevenfold increase. In cytokinin-depleted leaves the development of ribulose-1,5-bisphosphate carboxylase and NADP-glyceraldehydephosphate dehydrogenase was specifically, and markedly inhibited by actinomycin D. The inhibition was partially or even completely overcome after treatment with kinetin. However, under all conditions, RNA synthesis of the leaves, was only partially inhibited by actinomycin D. According to immunologic studies, all dark-grown leaves, in addition to the complete enzyme, contained an excess of free small subunit of ribulose-1,5-bisphosphate carboxylase that was absent in mature light-grown leaves. The most striking accumulation of free small subunit, protein occurred in cytokinin-depleted dark-grown leaves, indicating a deficiency of the plastidic synthesis of the large subunit. The capacity as well as the activity of plastidic protein synthesis was preferentially increased by cytokinin and light. Cytokinin increased, the amount of plastidic ribosomes per leaf and relative to the amount of cytoplasmic ribosomes. While the percentage of cytoplasmic ribosomes bound as polyribosomes was little affected by the cytokinin supply, the proportion of plastidic polyribosomes was increased from 11% to 18% after kinetin treatment of cytokinin-depleted leaves. In the light, the proportion of plastidic polyribosomes reached 39% of the total plastidic ribosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385123
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