Correlation Between the Development of Photorespiration and the Change in Activities of NH3 Assimilation Enzymes in Greening Oat Leaves

1991 ◽  
Vol 18 (6) ◽  
pp. 583 ◽  
Author(s):  
JW Yu ◽  
KC Woo
Keyword(s):  
Avena Sativa ◽  
Co2 Fixation ◽  
Chloroplast Development ◽  
Photosynthetic Capacity ◽  
Higher Plants ◽  
Glutamate Synthase ◽  
Chlorophyll Synthesis ◽  
Continuous Illumination ◽  
Bisphosphate Carboxylase ◽  
Glutamate Dehydrogenase Activity

The development of photosynthetic capacity and photorespiration during chloroplast development in 7-day-old etiolated oat (Avena sativa L.) primary leaves was investigated together with changes in the activity of possible NH3-assimilating enzymes. The development of photosynthetic CO2 fixation and photorespiration capacity, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and glutamine synthetase (GS) activities comparable to green leaves were completed within 48 h of continuous illumination. Chlorophyll synthesis and glutamate synthase (GOGAT) activity continued to increase beyond this time. Within this 48-h period, the activities of Rubisco, GS and GOGAT increased 2.3, 2 and 3 times repectively. Throughout the greening treatment, the GS and GOGAT activities were always high enough to sustain the expected rate of photorespiratory NH3 production. In contrast, glutamate dehydrogenase activity decreased during greening, and its measured rate was not high enough for photorespirtory NH3 assimilation. These results support the idea that the GS/GOGAT pathway is the major, if not the only, route for photorespiratory NH3 assimilation in the light in leaves of higher plants.

Photoregulation of chloroplast developm ent: transcriptional, translational and post-translational controls?

1983 ◽  
Vol 303 (1116) ◽  
pp. 419-431 ◽  
Keyword(s):  
Steady State ◽  
Translational Control ◽  
Nuclear Dna ◽  
Chloroplast Development ◽  
Light Harvesting ◽  
Limit Of Detection ◽  
Continuous Illumination ◽  
Steady State Concentration ◽  
Bisphosphate Carboxylase ◽  
State Concentration

Chloroplast development involves the nucleus, the cytoplasm and the chloroplast of plant cells. This may be illustrated by reference to the two most abundant proteins of the chloroplast: (i) the soluble CO 2 -fixing enzyme ribulose 1,5-bisphosphate carboxylase—oxygenase, whose large subunit (LSU) is encoded in chloroplast DNA and synthesized on chloroplast ribosomes and whose small subunit (SSU) is encoded in nuclear DNA, synthesized on cytoplasmic ribosomes in precursor form and transported into chloroplasts, and (ii) the thylakoid-bound light-harvesting chlorophyll a/b complex, whose pigment components are synthesized in the chloroplast and whose apoproteins resemble the SSU in site of coding and site of synthesis. We have examined the extent to which biosynthetic events in the nucleocytoplasmic compartments are coordinated with those inside the chloroplast during the de-etiolation of pea seedlings. We have examined the levels of LSU, SSU and the light-harvesting chlorophyll a/b protein (LHCP) by using a highly specific radioimmune assay. The steady-state levels of the corresponding mRNAs have been determined using specific cloned DNA probes. With the SSU, the mRNA and protein levels are near the limit of detection in dark-grown plants but increase markedly under continuous white light, with a lag of about 24 h. The protein appears to be under simple phytochrome control at the level of the steady-state concentration of its mRNA. The LSU also appears to be regulated through the steady-state concentration of its mRNA but in this case the mRNA is not under simple phytochrome control. The LHCP mRNA is readily detectable in dark-grown plants and accumulates further under illumination in a phytochrome-mediated manner. However, the LHCP itself (like chlorophyll) is not detectable in dark-grown plants and accumulates to high levels only under continuous illumination, with a lag of about 6 h. Post-translational control is particularly important in the accumulation of the LHCP: continuous chlorophyll synthesis is required for the stabilization of the protein within the thylakoid membrane, at least during the early stages of chloroplast development.

Photoregulation of the biosynthesis of ribulose bisphosphate carboxylase

Development ◽  
1984 ◽  
Vol 83 (Supplement) ◽  
pp. 163-178
Author(s):  
R. John Ellis ◽  
Thomas F. Gallagher ◽  
Gareth I. Jenkins ◽  
C. Ruth Lennox
Keyword(s):  
Chloroplast Development ◽  
Higher Plants ◽  
Large Subunit ◽  
Nuclear Genome ◽  
Small Subunit ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Subunit Mrna ◽  
Parallel Increase

Chloroplast development in higher plants is light dependent, and is accompanied by the synthesis of chlorophyll and the accumulation of many chloroplast polypeptides. There is a 100-fold greater content of the photosynthetic enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase, in light-grown seedlings of Pisum sativum than in dark-grown seedlings. Following the illumination of dark-grown seedlings, there is a parallel increase in the content of both the mRNA and the polypeptide of the small subunit of the carboxylase; this subunit is a product of the nuclear genome. The increases in the mRNA and the polypeptide of the large subunit, which is a product of the chloroplast genome, show less synchronicity. Studies with isolated leaf nuclei show that the increase in small subunit mRNA is mediated primarily at the level of transcription. Three distinct effects of light on transcription of small subunit genes have been found; a rapid (∼1 h) burst, followed by a decline, when etiolated plants are first exposed to light; a slow (∼36h) development of the competence to transcribe rapidly after the initial burst; rapid (∼20 min) switches in both directions when fully greened plants are exposed to light—dark transitions.

scholarly journals Mutation Mechanism of Leaf Color in Plants: A Review

Forests ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 851 ◽  
Author(s):  
Ming-Hui Zhao ◽  
Xiang Li ◽  
Xin-Xin Zhang ◽  
Heng Zhang ◽  
Xi-Yang Zhao
Keyword(s):  
Chloroplast Development ◽  
Higher Plants ◽  
Chlorophyll Synthesis ◽  
Economic Losses ◽  
Future Research ◽  
Leaf Color ◽  
Poor Growth ◽  
Existing Problems ◽  
Color Mutation ◽  
Development And Differentiation

Color mutation is a common, easily identifiable phenomenon in higher plants. Color mutations usually affect the photosynthetic efficiency of plants, resulting in poor growth and economic losses. Therefore, leaf color mutants have been unwittingly eliminated in recent years. Recently, however, with the development of society, the application of leaf color mutants has become increasingly widespread. Leaf color mutants are ideal materials for studying pigment metabolism, chloroplast development and differentiation, photosynthesis and other pathways that could also provide important information for improving varietal selection. In this review, we summarize the research on leaf color mutants, such as the functions and mechanisms of leaf color mutant-related genes, which affect chlorophyll synthesis, chlorophyll degradation, chloroplast development and anthocyanin metabolism. We also summarize two common methods for mapping and cloning related leaf color mutation genes using Map-based cloning and RNA-seq, and we discuss the existing problems and propose future research directions for leaf color mutants, which provide a reference for the study and application of leaf color mutants in the future.

scholarly journals SCARECROW gene function is required for photosynthetic development in maize

2020 ◽  
Author(s):  
Thomas E. Hughes ◽  
Jane A. Langdale
Keyword(s):  
Leaf Anatomy ◽  
Pyruvate Carboxylase ◽  
Chloroplast Development ◽  
Photosynthetic Capacity ◽  
Ribulose Bisphosphate Carboxylase ◽  
Wild Type ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Maize Leaves ◽  
Ribulose Bisphosphate Carboxylase Oxygenase

AbstractC4 photosynthesis in grasses relies on a specialized leaf anatomy. In maize, this ‘Kranz’ leaf anatomy is patterned in part by the duplicated SCARECROW (SCR) genes ZmSCR1 and ZmSCR1h. Here we show that in addition to patterning defects, chlorophyll content and levels of transcripts encoding Golden2-like regulators of chloroplast development are significantly lower in Zmscr1;Zmscr1h mutants than in wild-type. These perturbations are not associated with changes in chloroplast number, size or ultrastructure. However, the maximum rates of carboxylation by ribulose bisphosphate carboxylase/oxygenase (RuBisCO, Vcmax) and phosphoenolpyruvate carboxylase (PEPC, Vpmax) are both reduced, leading to perturbed plant growth. The CO2 compensation point and 13C‰ of Zmscr1;Zmscr1h plants are both normal, indicating that a canonical C4 cycle is operating, albeit at reduced overall capacity. Taken together, our results reveal that the maize SCR genes, either directly or indirectly, play a role in photosynthetic development.Significance statementSCARECROW (SCR) is one of the best studied plant developmental regulators, however, its role in downstream plant physiology is less well-understood. Here, we have demonstrated that SCR is required to establish and/or maintain photosynthetic capacity in maize leaves.

Measurement of ferrochelatase activity using a novel assay suggests that plastids are the major site of haem biosynthesis in both photosynthetic and non-photosynthetic cells of pea (Pisum sativum L.)

2002 ◽  
Vol 362 (2) ◽  
pp. 423-432 ◽  
Author(s):  
Johanna E. CORNAH ◽  
Jennifer M. ROPER ◽  
Davinder Pal SINGH ◽  
Alison G. SMITH
Keyword(s):  
Ferrous Iron ◽  
Specific Activity ◽  
Higher Plants ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Marker Enzyme ◽  
Hexane Extraction ◽  
Higher Plant ◽  
Major Site ◽  
Haem Biosynthesis

Ferrochelatase is the terminal enzyme of haem biosynthesis, catalysing the insertion of ferrous iron into the macrocycle of protoporphyrin IX, the last common intermediate of haem and chlorophyll synthesis. Its activity has been reported in both plastids and mitochondria of higher plants, but the relative amounts of the enzyme in the two organelles are unknown. Ferrochelatase is difficult to assay since ferrous iron requires strict anaerobic conditions to prevent oxidation, and in photosynthetic tissues chlorophyll interferes with the quantification of the product. Accordingly, we developed a sensitive fluorimetric assay for ferrochelatase that employs Co2+ and deuteroporphyrin in place of the natural substrates, and measures the decrease in deuteroporphyrin fluorescence. A hexane-extraction step to remove chlorophyll is included for green tissue. The assay is linear over a range of chloroplast protein concentrations, with an average specific activity of 0.68nmol·min−1·mg of protein−1, the highest yet reported. The corresponding value for mitochondria is 0.19nmol·min−1·mg of protein−1. The enzyme is inhibited by N-methylprotoporphyrin, with an estimated IC50 value of ≈ 1nM. Using this assay we have quantified ferrochelatase activity in plastids and mitochondria from green pea leaves, etiolated pea leaves and pea roots to determine the relative amounts in the two organelles. We found that, in all three tissues, greater than 90% of the activity was associated with plastids, but ferrochelatase was reproducibly detected in mitochondria, at levels greater than the contaminating plastid marker enzyme, and was latent. Our results indicate that plastids are the major site of haem biosynthesis in higher plant cells, but that mitochondria also have the capacity for haem production.

scholarly journals Plastid-Localized EMB2726 Is Involved in Chloroplast Biogenesis and Early Embryo Development in Arabidopsis

2021 ◽  
Vol 12 ◽  
Author(s):  
Chuanling Li ◽  
Jian-Xiu Shang ◽  
Chenlei Qiu ◽  
Baowen Zhang ◽  
Jinxue Wang ◽  
...  
Keyword(s):  
Chloroplast Development ◽  
Developmental Process ◽  
Higher Plants ◽  
Critical Role ◽  
Elongation Factor ◽  
Early Embryo ◽  
The Body ◽  
Insertion Mutant ◽  
Cell Stage ◽  
Dna Insertion

Embryogenesis is a critical developmental process that establishes the body organization of higher plants. During this process, the biogenesis of chloroplasts from proplastids is essential. A failure in chloroplast development during embryogenesis can cause morphologically abnormal embryos or embryonic lethality. In this study, we isolated a T-DNA insertion mutant of the Arabidopsis gene EMBRYO DEFECTIVE 2726 (EMB2726). Heterozygous emb2726 seedlings produced about 25% albino seeds with embryos that displayed defects at the 32-cell stage and that arrested development at the late globular stage. EMB2726 protein was localized in chloroplasts and was expressed at all stages of development, such as embryogenesis. Moreover, the two translation elongation factor Ts domains within the protein were critical for its function. Transmission electron microscopy revealed that the cells in emb2726 embryos contained undifferentiated proplastids and that the expression of plastid genome-encoded photosynthesis-related genes was dramatically reduced. Expression studies of DR5:GFP, pDRN:DRN-GFP, and pPIN1:PIN1-GFP reporter lines indicated normal auxin biosynthesis but altered polar auxin transport. The expression of pSHR:SHR-GFP and pSCR:SCR-GFP confirmed that procambium and ground tissue precursors were lacking in emb2726 embryos. The results suggest that EMB2726 plays a critical role during Arabidopsis embryogenesis by affecting chloroplast development, possibly by affecting the translation process in plastids.

Ammonia, glutamine, and asparagine: a carbon–nitrogen interface

1988 ◽  
Vol 66 (10) ◽  
pp. 2103-2109 ◽  
Author(s):  
K. W. Joy
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Higher Plants ◽  
Amino Nitrogen ◽  
Glutamate Synthase ◽  
Dinitrogen Fixation ◽  
Similar Function ◽  
Metabolic Processes ◽  
Organic Form ◽  
Primary Input

In plants, the primary input of nitrogen (obtained from the soil or from symbiotic dinitrogen fixation) occurs through the assimilation of ammonia into organic form. Synthesis of glutamine (via glutamine synthetase) is the major, and possibly exclusive, route for this process, and there is little evidence for the participation of glutamate dehydrogenase. A variety of reactions distribute glutamine nitrogen to other compounds, including transfer to amino nitrogen through glutamate synthase. In many plants asparagine is a major recipient of glutamine nitrogen and provides a mobile reservoir for transport to sites of growth; ureides perform a similar function in some legumes. Utilisation of transport forms of nitrogen, and a number of other metabolic processes, involves release of ammonia, which must be reassimilated. In illuminated leaves, there is an extensive flux of ammonia released by the photorespiratory cycle, requiring continuous efficient reassimilation. Aspects of ammonia recycling and related amide metabolism in higher plants are reviewed.

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