Comparison of the effects of cytokinins on enzyme development in different cell compartments of the shoot organs of rye seedlings
TL;DR: Variation in cytokinin supply has different effects on protein formation and enzyme development in primary leaves and coleoptiles of rye seedlings and subsequent addition of kinetin enhances the decay of protein and most of the enzyme activities determined and thus, in a similar way to the effect of light, seems to promote the senescence of the co-optiles.
About: This article is published in Zeitschrift für Pflanzenphysiologie.The article was published on 1974-03-01. It has received 25 citations till now. The article focuses on the topics: Cytokinin & Kinetin.
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TL;DR: Glyoxysome Biogenesis of Leaf Peroxisomes and Hormonal Influences: Foundations of Microbody Transition in Fatty Cotyledons.
Abstract: INTRODUCTION 159 SOURCES OF MICROBODIES: MICROBODY CONSTITUENTS 162 Glyoxysomes...... ....... ........ ... ...... ... ..... 162 Leaf Peroxisomes 164 Microbodies from Other Tissues ...... 164 DISTRIBUTION OF ENZYMES WITHIN MICROBODIES 165 ISOENZYMES IN GLYOXYSOMES AND LEAF PEROXISOMES 166 Isoenzymes of MDH 166 Isoenzymes of Citrate Synthetase 167 Isoenzymes of Aspartate-a.-Ketoglutarate Transaminase 168 FUNCTIONS OF GLYOXYSOMES AND LEAF PEROXISOMES 168 DEVELOPMENT OF MICROBODIES 170 Glyoxysome Biogenesis ..... ,", . . . . . . . . . . . . . . ,. 170 Biogenesis of Leaf Peroxisomes 176 Microbody Transition in Fatty Cotyledons 177 Hormonal Influences 185 CONCLUSIONS , ...... , 186
386 citations
TL;DR: Although indications are presented that the promotion of chloroplast development by cytokinins is closely connected with a stimulation of the gene expression program for plastogenesis, other sites of hormone action cannot be excluded and are discussed in the last part of the review.
139 citations
TL;DR: It is concluded that cytoplasmic protein synthesis must contribute a functional chloroplasts envelope including the mechanism for the recognition and uptake of chloroplast proteins which are synthesized on cytopLasmic ribosomes.
Abstract: 1. In developing rye (Secale cereale L.) leaves the formation of plastidic ribosomes was selectively prevented in light as well as in darkness, when the seedlings were grown at an elevated temperature of 32° instead of 22° where normal development ocurred. Plastid ribosome deficient parts of lightgrown leaves were chlorotic at 32°. — 2. At both temperatures the leaves contained under all conditions (light or dark, on H2O or nutrient solution) equal or very similar amounts of total amino nitrogen. In light, the contents of total protein and dry weight were lower at 32° than at 22°, especially when the plants were grown on nutrient solution. — 3. Mitochondrial marker enzymes had normal or even higher activities in 32°-grown leaves. Respiration rates were similar for segments of leaves grown on water in light either at 32° or at 22° but by 20–30% lower for 32°-grown plants when they had been raised in darkness or on nutrient solution. In contrast to 22°-grown tissue, respiration of 32°-grown leaf segments was rather insensitive to KCN. Comparative inhibitor studies indicated the presence of both the cyanide-sensitive and the cyanide-insensitive pathway of respiration in 32°-grown leaves. — 4. Leaf microbody marker enzymes were present in leaves grown at 32°. From chlorotic parts of 32°-light-grown leaves a typical microbody fraction was isolated on sucrose densitygradients. — 5. Leaves of seedlings grown at 32° contained only very low levels of ribulosediphosphate carboxylase activity and of fraction I protein. Photosynthetic 14CO2-fixation of such leaves was only a few per cent of that observed in normal leaves, and no photosynthetic oxygen evolution was observed in chlorotic leaf segments. However, ten other soluble enzymes which are exclusively or partially localized in chloroplasts reached high activities under all conditions at 32° (Table 4). — 6. From chlorotic parts of 32°-light-grown leaves as well as from etiolated 32°-grown leaves a fraction of intact plastids was isolated and purified by sucrose gradient centrifugation which contained several soluble chloroplast enzymes. From the results we conclude that cytoplasmic protein synthesis must contribute a functional chloroplast envelope including the mechanism for the recognition and uptake of chloroplast proteins which are synthesized on cytoplasmic ribosomes.
113 citations
TL;DR: In green and etiolated leaves of rye (Secale cereale L. ev. "Halo" as mentioned in this paper ) exposed to strong light at low temperature (0.4°C) catalase was inactivated.
Abstract: In green as well as in etiolated leaves of rye (Secale cereale L. ev. ‘Halo’), exposed to strong light at low temperature (0.4°C) catalase was inactivated. Other heme-containing enzymes (peroxidases) and various enzymes of photosynthetic, photorespiratory or peroxide metabolism were not photoinactivated. After returning plants from a low to a physiological temperature (22°C), catalase activity recovered within 12 h through new synthesis. The leaf contents of H2O2 and organic peroxides were not affected by the photoinactivation of catalse. The content of malondialdehyde generally increased after exposure to a higher light intensity. High-light-induced increases of ascorbate, and particularly of glutathione, were more marked in catalase-deficient than in normal leaves. Photoinactivation of catalase was accompanied by severe inhibition of photosynthesis. Photoinhibition of photosynthesis was not related to the lack of catalase because photosynthesis was not impaired when catalase activity was kept low by growing the plants under non-photorespiratory conditions. Photoinhibition appeared to result from photodamage in primary photochemistry of photosystem II, as indicated by a decrease of the maximal variable fluorescence. Photoinhibition of photosynthesis and of catalase have in common that in both instances proteins are involved that are continuously inactivated in light and, therefore, particularly sensitive to stress conditions that prevent their replacement by repair synthesis.
87 citations
References
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TL;DR: A spectrophotometric method of measuring the enzymatic formation and disappearance of umaric and cis -aconitic acids is reported.
746 citations
545 citations
TL;DR: Through separation of proteins by electrofocusing, by Sephadex 6200 column chromatography, and by starch gel and polyacryl- amide gel electrophoresis, it was shown that a single peroxiso- mal protein catalyzed these reactions.
173 citations
TL;DR: Cultured tobacco tissue possesses proplastids capable of differentiating into mature chloroplasts; the absence of this compound results in a blockage of the formation of grana, and the possibility that kinetin exerts a direct effect upon chloroplast differentiation is considered.
Abstract: Cultured tobacco tissue possesses proplastids capable of differentiating into mature chloroplasts. Kinetin (6-furfurylaminopurine) is a specific requirement for this differentiation; the absence of this compound results in a blockage of the formation of grana. The possibility that kinetin exerts a direct effect upon chloroplast differentiation is considered.
136 citations
TL;DR: In cotyledons of sunflower seedlings glyoxysomal and peroxisomal enzymes exhibit different rates of development during germination, and it is proposed that malate and aspartate may be involved in hydrogen transport between microbodies and other cellular sites.
Abstract: In cotyledons of sunflower seedlings glyoxysomal and peroxisomal enzymes exhibit different rates of development during germination. The total activity of isocitrate lyase, a glyoxysomal marker enzyme, rapidly increased during the first 3 days, and then decreased 89% by day 9. Exposure to light accelerated this decrease only slightly. The specific activity of glyoxysomal enzymes (malate synthetase, isocitrate lyase, citrate synthetase, and aconitase) in the microbody fraction from sucrose density gradients increased between days 2 and 4 about 2- to 3-fold, and thereafter it remained about constant in light or darkness.Total activity of the peroxisomal enzymes increased slowly in the dark during the first 4 days of germination and thereafter remained at a constant level of activity in the dark or increased 2-fold in 24 hours of light. The specific activties of glycolate oxidase, hydroxypyruvate reductase, and serine-glyoxylate aminotransferase in the isolated microbody fraction increased about 10-fold between days 2 and 4 in the dark and then remained constant or increased again 10-fold after an additional 48 hours in the light.The total activity of the common microbody marker, catalase, developed similarly to isocitrate lyase, but decreased only 72% by day 9. The specific activities of enzymes (catalase, malate dehydrogenase, and aspartate aminotransferase) common to both microbody systems were 10- to 1000-fold greater than those of other enzymes. It is proposed that malate and aspartate may be involved in hydrogen transport between microbodies and other cellular sites.Glutamate-glyoxylate aminotransferase was very active in microbodies from castor bean endosperm and sunflower cotyledons. The specific activity of this aminotransferase developed similarly to glyoxysomal enzymes in the dark but further increased in the light, as did peroxisomal enzymes.The microbody fraction of castor bean endosperm germinated in the dark for 5 days contained both glyoxysomal and peroxisomal enzymes of similar specific activity.Adjacent to the microbody fraction on sucrose gradients from sunflower cotyledons were etioplasts at slightly lower densities and protein bodies at similar and higher densities. Their presence in the microbody fractions resulted in artificially low specific activities.
132 citations