Incorporation of [14C] carbon dioxide and [2-14C] mevalonic acid into terpenoids of higher plants during chloroplast development.
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ABSTRACT:
SUBMITTER: Treharne KJ
PROVIDER: S-EPMC1264981 | biostudies-other | 1966 Apr
REPOSITORIES: biostudies-other
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Project description:1. Chloroplasts prepared by the non-aqueous technique will, after fragmentation by ultrasonic treatment, incorporate [2-(14)C]mevalonic acid into phytoene, the first C(40) compound formed in the biosynthetic sequence to coloured carotenoids. 2. With suspensions containing 3.5mg. of chlorophyll, the optimum amounts of cofactor required were ATP (10mumoles), magnesium chloride (20mumoles) and glutathione (20mumoles); neither NAD(+) nor NADP(+) was required. 3. Very small amounts of squalene are also formed and synthesis is stimulated by addition of NADH or NADPH. Phytoene synthesis was not affected by the presence of these cofactors and no lycopersene (the C(40) homologue of squalene) was detected. 4. The phytol side chain of chlorophyll is also labelled under these conditions. 5. Preparations of developing chloroplasts are more active than preparations of mature chloroplasts.
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Project description:Many eukaryotic green algae possess biophysical carbon-concentrating mechanisms (CCMs) that enhance photosynthetic efficiency and thus permit high growth rates at low CO2 concentrations. They are thus an attractive option for improving productivity in higher plants. In this study, the intracellular locations of ten CCM components in the unicellular green alga Chlamydomonas reinhardtii were confirmed. When expressed in tobacco, all of these components except chloroplastic carbonic anhydrases CAH3 and CAH6 had the same intracellular locations as in Chlamydomonas. CAH6 could be directed to the chloroplast by fusion to an Arabidopsis chloroplast transit peptide. Similarly, the putative inorganic carbon (Ci) transporter LCI1 was directed to the chloroplast from its native location on the plasma membrane. CCP1 and CCP2 proteins, putative Ci transporters previously reported to be in the chloroplast envelope, localized to mitochondria in both Chlamydomonas and tobacco, suggesting that the algal CCM model requires expansion to include a role for mitochondria. For the Ci transporters LCIA and HLA3, membrane location and Ci transport capacity were confirmed by heterologous expression and H(14) CO3 (-) uptake assays in Xenopus oocytes. Both were expressed in Arabidopsis resulting in growth comparable with that of wild-type plants. We conclude that CCM components from Chlamydomonas can be expressed both transiently (in tobacco) and stably (in Arabidopsis) and retargeted to appropriate locations in higher plant cells. As expression of individual Ci transporters did not enhance Arabidopsis growth, stacking of further CCM components will probably be required to achieve a significant increase in photosynthetic efficiency in this species.
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Project description:1. The patterns of incorporation of (14)C into glycerolipid fatty acids of developing maize leaf lamina from supplied [1-(14)C]acetate and from (14)CO(2) during steady-state photosynthesis were similar. Oleate of phosphatidylcholine and palmitate of phosphatidylglycerol attained linear rates of labelling more rapidly than did other fatty acids, particularly the linoleate and linolenate of monogalactosyl diacylglycerol. 2. After the transfer of lamina from labelled to unlabelled acetate, there was a decrease in labelled oleate and linoleate of phosphatidylcholine and a concomitant increase in the amount of radioactivity in the linoleate and linolenate of monogalactosyl diacylglycerol. 3. The rapidly labelled phospholipids, phosphatidylcholine and phosphatidylglycerol, were shown by differential and sucrose-density-gradient centrifugation to be associated with different organelles, the former being mainly in a low-density membrane fraction, probably microsomal, and the latter mainly in chloroplasts. 4. During a 48h period after supplying spinach leaves with [(14)C]acetate, radioactivity was lost from the oleate of phosphatidylcholine present in fractions sedimented at 12000g and 105000g, and accumulated in the linolenate of monogalactosyl diacylglycerol of the chloroplast. 5. It is proposed that the phosphatidylcholine of some non-plastid membranes is intimately involved in the process of oleate desaturation and that this lipid serves as a donor of unsaturated C(18) fatty acids to other lipids, principally monogalactosyl diacylglycerol, of the chloroplasts.
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Project description:1. [14C]Acetylcholine synthesis and 14CO2 production from [U-14C]glucose has been measured in tissue prism preparations from human neocortex. 2. Electron micrographs of prisms from human and rat neocortex show that both contain intact synaptic endings with evenly-distributed vesicles and normal-appearing mitochondria, but only poorly preserved cell body structure. 3. Synthesis of [14C]acetylcholine in prisms from rat neocortex is similar to estimates for turnover in vivo. Synthesis in prisms from human neocortex is 18% of that in rat tissue and 64% of that in tissue from baboon neocortex for incubations performed in 31 mM-K+. 4. Investigations of prisms prepared from rat brains stored at 37 degrees C after death revealed that synthesis of [14C]acetylcholine in the presence of 31 mM-K+ was greatly decreased within 30 min of post-mortem incubation, whereas synthesis at 5 mM-K+ and production of 14CO2 at both K+ concentrations were only significantly affected after longer periods. Changes were similar in neocortex and striatum. Thus human autopsy material is unlikely to be suitable for use with this system. 5. Investigations using animal models suggest that [14C]acetylcholine synthesis and 14CO2 production are not affected by surgical or anaesthetic procedures. 6. Neither [14C]acetylcholine synthesis nor 14CO2 production in human prisms was significantly changed with age between 15 and 68 years. 7. Samples from patients with the dementing condition Alzheimer's disease showed a significant decrease in [14C]acetylcholine synthesis to 47% of normal samples and a significant increase of 39% in production of 14CO2.
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Project description:Pea leaves were illuminated in air containing 150 or 1000p.p.m. of 14CO2 for various times. Alternatively, segments of wheat leaves were supplied with [3-14C]serine for 40 min in the light in air with 145, 326 or 944p.p.m. of 12CO2. Sucrose was extracted from the leaf material, hydrolysed with invertase, and 14C in the pairs of carbon atoms C-3+C-4, C-2+C-5 and C-1+C-6 in the glucose moiety was measured. The results obtained after metabolism of 14CO2 were consistent with the operation of the photosynthetic carbon-reduction cycle; the effects of CO2 concentration on distribution of 14C in the carbon chain of glucose after metabolism of [3-14C]serine is more easily explained by metabolism through the glycollate pathway than by the carbon-reduction cycle.
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Project description:BackgroundChloroplast genomes evolve slowly and many primers for PCR amplification and analysis of chloroplast sequences can be used across a wide array of genera. In some cases 'universal' primers have been designed for the purpose of working across species boundaries. However, the essential information on these primer sequences is scattered throughout the literature.ResultsA database is presented here which assembles published primer information for chloroplast DNA. Additional primers were designed to fill gaps where little or no primer information could be found. Amplicons are either the genes themselves (typically useful in studies of sequence variation in higher-order phylogeny) or they are spacers, introns, and intergenic regions (for studies of phylogeographic patterns within and among species). The current list of 'generic' primers consists of more than 700 sequences. Wherever possible, we give the locations of the primers in the thirteen fully sequenced chloroplast genomes (Nicotiana tabacum, Atropa belladonna, Spinacia oleracea, Arabidopsis thaliana, Populus trichocarpa, Oryza sativa, Pinus thunbergii, Marchantia polymorpha, Zea mays, Oenothera elata, Acorus calamus, Eucalyptus globulus, Medicago trunculata).ConclusionThe database described here is designed to serve as a resource for researchers who are venturing into the study of poorly described chloroplast genomes, whether for large- or small-scale DNA sequencing projects, to study molecular variation or to investigate chloroplast evolution.
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Project description:Photosynthetic and respiratory exchanges of CO(2) by plants with the atmosphere are significantly larger than anthropogenic CO(2) emissions, and these fluxes will change as growing conditions are altered by climate change. Understanding feedbacks in CO(2) exchange is important to predicting future atmospheric [CO(2)] and climate change. At the tissue and plant scale, respiration is a key determinant of growth and yield. Although the stimulation of C(3) photosynthesis by growth at elevated [CO(2)] can be predicted with confidence, the nature of changes in respiration is less certain. This is largely because the mechanism of the respiratory response is insufficiently understood. Molecular, biochemical and physiological changes in the carbon metabolism of soybean in a free-air CO(2) enrichment experiment were investigated over 2 growing seasons. Growth of soybean at elevated [CO(2)] (550 micromol x mol(-1)) under field conditions stimulated the rate of nighttime respiration by 37%. Greater respiratory capacity was driven by greater abundance of transcripts encoding enzymes throughout the respiratory pathway, which would be needed for the greater number of mitochondria that have been observed in the leaves of plants grown at elevated [CO(2)]. Greater respiratory quotient and leaf carbohydrate content at elevated [CO(2)] indicate that stimulated respiration was supported by the additional carbohydrate available from enhanced photosynthesis at elevated [CO(2)]. If this response is consistent across many species, the future stimulation of net primary productivity could be reduced significantly. Greater foliar respiration at elevated [CO(2)] will reduce plant carbon balance, but could facilitate greater yields through enhanced photoassimilate export to sink tissues.
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Project description:1. The incorporation of (14)C into the brain glycogen of conscious rabbits with labelled glucose, bicarbonate and glutamate as precursors has been studied. 2. Substantial incorporation from all these precursors was demonstrated after an interval of 5hr. from their injection. 3. With [(14)C]glucose maximal incorporation occurred at about 8hr. from the time of injection. 4. Hydrocortisone led to increased incorporation of (14)C from labelled glucose. 5. Some comparisons between the turnover of brain glycogen and that of skeletal and cardiac muscle are reported.
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Project description:Plant growth response to elevated levels of CO2 in the environment needs to be deeply investigated to understand the impact of rising global carbon dioxide levels. While the response of plants directly exposed to elevated CO2 is relatively well-studied, the trans-generational impact of elevated CO2 exposure in plants returned to ambient conditions is unexplored. In this study, we show that plants develop a trans-generational memory of elevated CO2 exposure in the next generation even after returning the plants to ambient CO2 levels. By analysing whole genome methylation, we identified that cytosine DNA methylation mechanisms are key to both initiate and maintain this epigenetic memory across generations. Grant ID: EF-1921724 Grant Title: Revealing how epigenetic inheritance governs the environmental challenge response with transformative 3D genomics and machine learning Funding Source: National Science Foundation (NSF)
2023-03-20 | GSE215743 | GEO