scholarly journals Dynamic Remodeling of the Plastid Envelope Membranes – A Tool for Chloroplast Envelope in vivo Localizations

2012 ◽  
Vol 3 ◽  
Author(s):  
Frederique K. H. Breuers ◽  
Andrea Bräutigam ◽  
Stefan Geimer ◽  
Ulla Y. Welzel ◽  
Giovanni Stefano ◽  
...  
Keyword(s):  
Chloroplast Envelope ◽  
Plastid Envelope ◽  
Envelope Membranes

Nitrate metabolism in relation to the aspartate-type C-4 pathway of photosynthesis in Eleusine coracana

1974 ◽  
Vol 52 (12) ◽  
pp. 2599-2605 ◽  
Author(s):  
C. K. M. Rathnam ◽  
V. S. R. Das
Keyword(s):  
Glutamate Dehydrogenase ◽  
Eleusine Coracana ◽  
Bundle Sheath ◽  
Chloroplast Envelope ◽  
Mesophyll Cells ◽  
Bundle Sheath Cells ◽  
Nitrate Metabolism ◽  
Type C ◽  
Envelope Membranes ◽  
Sheath Cells

The intercellular and intracellular distributions of nitrate assimilating enzymes were studied. Nitrate reductase was found to be localized on the chloroplast envelope membranes. The chloroplastic NADPH – glutamate dehydrogenase was concentrated in the mesophyll cells. The extrachloroplastic NADH – glutamate dehydrogenase was localized in the bundle sheath cells. Glutamate synthesized in the mesophyll chloroplasts was interpreted to be utilized exclusively in the synthesis of aspartate, while in the bundle sheath cells it was thought to be consumed in other cellular metabolic processes. Based on the results, a scheme is proposed to account for the nitrate metabolism in the leaves of Eleusine coracana Gaertn. in relation to its aspartate-type C-4 pathway of photosynthesis.

Mechanism of protein import across the chloroplast envelope

2000 ◽  
Vol 28 (4) ◽  
pp. 485-491 ◽  
Author(s):  
K. Chen ◽  
X. Chen ◽  
D. J. Schnell
Keyword(s):  
Protein Import ◽  
Essential Elements ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Subunits ◽  
Targeting Signals ◽  
Outer Envelope Membrane ◽  
Envelope Membranes

The development and maintenance of chloroplasts relies on the contribution of protein subunits from both plastid and nuclear genomes. Most chloroplast proteins are encoded by nuclear genes and are post-translationally imported into the organelle across the double membrane of the chloroplast envelope. Protein import into the chloroplast consists of two essential elements: the specific recognition of the targeting signals (transit sequences) of cytoplasmic preproteins by receptors at the outer envelope membrane and the subsequent translocation of preproteins simultaneously across the double membrane of the envelope. These processes are mediated via the co-ordinate action of protein translocon complexes in the outer (Toe apparatus) and inner (Tic apparatus) envelope membranes.

scholarly journals TIP family aquaporins play role in chloroplast osmoregulation and photosynthesis

2020 ◽  
Author(s):  
Azeez Beebo ◽  
Ahmad Zia ◽  
Christopher R. Kinzel ◽  
Andrei Herdean ◽  
Karim Bouhidel ◽  
...  
Keyword(s):  
Electron Transport ◽  
Oxygen Evolution ◽  
Photosynthetic Electron Transport ◽  
Chloroplast Envelope ◽  
Photosynthetic Oxygen Evolution ◽  
Wild Type ◽  
Thylakoid Lumen ◽  
Photosynthetic Oxygen ◽  
Osmotic Treatment ◽  
Envelope Membranes

SUMMARYPhotosynthetic oxygen evolution by photosystem II requires water supply into the chloroplast to reach the thylakoid lumen. A rapid water flow is also required into the chloroplast for optimal oxygen evolution and to overcome osmotic stress. The mechanisms governing water transport in chloroplasts are largely unexplored. Previous proteomics indicated the presence of three aquaporins from the tonoplast intrinsic protein (TIP) family, TIP1;1, TIP1;2 and TIP2;1, in chloroplast membranes of Arabidopsis thaliana. Here we revisited their location and studied their role in chloroplasts. Localization experiments indicated that TIP2;1 resides in the thylakoid, whereas TIP1;2 is present in both thylakoid and envelope membranes. Mutants lacking TIP1;2 and/or TIP2;1 did not display a macroscopic phenotype when grown under standard conditions. The mutant chloroplasts and thylakoids underwent less volume changes than the corresponding wild type preparations upon osmotic treatment and in the light. Significantly reduced rates of photosynthetic electron transport were obtained in the mutant leaves, with implications on the CO2 fixation rates. However, electron transport rates did not significantly differ between mutants and wild type when isolated thylakoids were examined. Less acidification of the thylakoid lumen was measured in mutants thylakoids, resulting in a slower induction of delta pH-dependent photoprotective mechanisms. These results identify TIP1;2 and TIP2;1 as chloroplast proteins and highlight their importance for osmoregulation and optimal photosynthesis. A third aquaporin, TIP1;1, is present in the chloroplast envelope, and may play role in photosynthesis under excessive light conditions, as based on the weak photosynthetic phenotype of its mutant.

Proteomics of chloroplast envelope membranes

2003 ◽  
Vol 78 (3) ◽  
pp. 205-230 ◽  
Author(s):  
Norbert Rolland ◽  
Myriam Ferro ◽  
Daphné Seigneurin-Berny ◽  
Jérôme Garin ◽  
Roland Douce ◽  
...  
Keyword(s):  
Chloroplast Envelope ◽  
Envelope Membranes

Importance of diacylglycerol in glycerolipid biosynthesis by spinach chloroplast envelope membranes

1994 ◽  
Vol 33 (1-2) ◽  
pp. 105-118 ◽  
Author(s):  
Jacques Joyard ◽  
Eric Maréchal ◽  
Agnès Malherbe ◽  
Maryse A. Block ◽  
Roland Douce
Keyword(s):  
Chloroplast Envelope ◽  
Spinach Chloroplast ◽  
Envelope Membranes

Plastid Envelope Membranes and the Dynamics of Plant Membrane Biogenesis

1992 ◽  
pp. 77-92
Author(s):  
Roland Douce ◽  
Maryse A. Block ◽  
Eric Maréchal ◽  
Albert-Jean Dorne ◽  
Jacques Joyard
Keyword(s):  
Membrane Biogenesis ◽  
Plastid Envelope ◽  
Envelope Membranes

scholarly journals Maize defective kernel5 is a bacterial TamB homologue required for chloroplast envelope biogenesis

2019 ◽  
Vol 218 (8) ◽  
pp. 2638-2658 ◽  
Author(s):  
Junya Zhang ◽  
Shan Wu ◽  
Susan K. Boehlein ◽  
Donald R. McCarty ◽  
Gaoyuan Song ◽  
...  
Keyword(s):  
Inorganic Phosphate ◽  
Phosphate Uptake ◽  
Soluble Sugars ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Double Membrane ◽  
Plastid Envelope ◽  
Membrane Envelope ◽  
Bacterial Outer Membrane ◽  
Outer Membrane Biogenesis

Chloroplasts are of prokaryotic origin with a double-membrane envelope separating plastid metabolism from the cytosol. Envelope membrane proteins integrate chloroplasts with the cell, but envelope biogenesis mechanisms remain elusive. We show that maize defective kernel5 (dek5) is critical for envelope biogenesis. Amyloplasts and chloroplasts are larger and reduced in number in dek5 with multiple ultrastructural defects. The DEK5 protein is homologous to rice SSG4, Arabidopsis thaliana EMB2410/TIC236, and Escherichia coli tamB. TamB functions in bacterial outer membrane biogenesis. DEK5 is localized to the envelope with a topology analogous to TamB. Increased levels of soluble sugars in dek5 developing endosperm and elevated osmotic pressure in mutant leaf cells suggest defective intracellular solute transport. Proteomics and antibody-based analyses show dek5 reduces levels of Toc75 and chloroplast envelope transporters. Moreover, dek5 chloroplasts reduce inorganic phosphate uptake with at least an 80% reduction relative to normal chloroplasts. These data suggest that DEK5 functions in plastid envelope biogenesis to enable transport of metabolites and proteins.

Lipid Labelling in Intact Chloroplasts from Exogenous Nucleotide Precursors

1981 ◽  
Vol 36 (1-2) ◽  
pp. 62-70 ◽  
Author(s):  
Margrit Bertrams ◽  
Käthe Wrage ◽  
Ernst Heinz
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
De Novo ◽  
Membrane System ◽  
Chloroplast Envelope ◽  
Label Free ◽  
Intact Chloroplasts ◽  
Time Required

Abstract De novo-synthesis of glycerolipids in chloroplasts is initiated by a stroma enzyme which catalyzes the formation of lyso-phosphatidic acid from glycerophosphate and acyl-CoA. When these substrates are added to isolated, intact chloroplasts, only glycerophosphate can readily pass through the chloroplast envelope which represents a permeation barrier for acyl-CoA, although higher thioester concentrations destroy this membrane system. At low concentrations of acyl-CoA, which do not impair the envelope, intact chloroplasts metabolize exogenous acyl-CoA in two ways to give free fatty acids and labelled phosphatidyl choline. This indicates that the envelope thioesterase can use exogenous substrates. Isolated, intact chloroplasts fixing radioactive CO2 label free fatty acids and acylglycerols but not galactolipids, since they cannot convert 3-phosphoglycerate into UDP-galactose which in vivo is supplied by the cytoplasm. This cooperation was simulated in vitro by adding all enzymes and cofactors necessary for conversion of 3-phosphoglycerate into UDP-galactose to intact chloro­plasts which then formed labelled monogalactosyl diacylglycerol from labelled CO2. The time required to transfer envelope-made galactolipids from the envelope into thylakoids was studied by incubating intact chloroplasts with radioactive UDP-galactose, subsequent osmotic disruption of organelles with concomitant enzymatic degradation of UDP-galactose followed by separation of envelopes and thylakoids. Only after short times (< 1min) appreciable proportions 920-30%) of radioactive galactolipid export from envelopes into thylakoids.

scholarly journals Thermal Damage to Chloroplast Envelope Membranes

1989 ◽  
Vol 90 (2) ◽  
pp. 606-609 ◽  
Author(s):  
Douglas C. McCain ◽  
Judith Croxdale ◽  
John L. Markley
Keyword(s):  
Thermal Damage ◽  
Chloroplast Envelope ◽  
Envelope Membranes

scholarly journals Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

2016 ◽  
Vol 113 (38) ◽  
pp. 10714-10719 ◽  
Author(s):  
Amélie A. Kelly ◽  
Barbara Kalisch ◽  
Georg Hölzl ◽  
Sandra Schulze ◽  
Juliane Thiele ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Lipid Transfer ◽  
Terminal Sequence ◽  
Outer Envelope ◽  
Outer Envelope Membrane ◽  
Envelope Reconstruction ◽  
Envelope Membranes

Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.

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