scholarly journals Role of Galactolipids in Plastid Differentiation Before and After Light Exposure

Plants ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 357 ◽  
Author(s):  
Fujii ◽  
Wada ◽  
Kobayashi
Keyword(s):  
Thylakoid Membrane ◽  
Protein Complexes ◽  
Light Exposure ◽  
Chlorophyll Biosynthesis ◽  
Membrane Structures ◽  
Plastid Differentiation ◽  
Internal Membrane ◽  
Before And After ◽  
Pigment Protein Complexes ◽  
Cotyledon Cells

Galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are the predominant lipid classes in the thylakoid membrane of chloroplasts. These lipids are also major constituents of internal membrane structures called prolamellar bodies (PLBs) and prothylakoids (PTs) in etioplasts, which develop in the cotyledon cells of dark-grown angiosperms. Analysis of Arabidopsis mutants defective in the major galactolipid biosynthesis pathway revealed that MGDG and DGDG are similarly and, in part, differently required for membrane-associated processes such as the organization of PLBs and PTs and the formation of pigment–protein complexes in etioplasts. After light exposure, PLBs and PTs in etioplasts are transformed into the thylakoid membrane, resulting in chloroplast biogenesis. During the etioplast-to-chloroplast differentiation, galactolipids facilitate thylakoid membrane biogenesis from PLBs and PTs and play crucial roles in chlorophyll biosynthesis and accumulation of light-harvesting proteins. These recent findings shed light on the roles of galactolipids as key facilitators of several membrane-associated processes during the development of the internal membrane systems in plant plastids.

The Influence of 5-Aminolevulinic Acid on Protochlorophyllide and Protochlorophyll Accumulation in Dark-Grown Scenedesmus

1990 ◽  
Vol 45 (1-2) ◽  
pp. 71-73 ◽  
Author(s):  
Kiriakos Kotzabasis ◽  
Horst Senger
Keyword(s):  
Aminolevulinic Acid ◽  
Protein Complexes ◽  
Chlorophyll Biosynthesis ◽  
Scenedesmus Obliquus ◽  
Good Tool ◽  
Future Studies ◽  
Pigment Protein Complexes ◽  
Kinetics Of ◽  
Grown Culture ◽  
In Cells

The intermediate of chlorophyll biosynthesis, 5-aminolevulinic acid (ALA ), is a necessary prerequisite for the formation of protochlorophyllide (PChlide) and protochlorophyll (PChl) in the dark. The application of ALA to a dark-grown culture of the pigment mutant C-2 A′ of Scenedesmus obliquus increased the amount of PChlide 30-fold and the amount of PChl about 10-fold. The rates of ALA-dependent formation of PChlide and PChl reach their maximum values at different concentrations of added ALA . Similarly, the kinetics of PChlide and PChl formation in cells incubated with ALA are different. Cells of Scenedesmus mutant C-2 A′ incubated with various concentrations of ALA for different periods provide a good tool for future studies differentiating between PChlide and PChl metabolism . − The incorporation of Chl deriving from either PChl or PChlide into different pigment protein complexes is discussed.

Heat-Induced Alterations in Thylakoid Membrane Protein Composition in Barley

1994 ◽  
Vol 21 (6) ◽  
pp. 759 ◽  
Author(s):  
TS Takeuchi ◽  
JP Thornber
Keyword(s):  
Thylakoid Membrane ◽  
Elevated Temperatures ◽  
Quaternary Structure ◽  
Protein Complexes ◽  
Protein Composition ◽  
Spectroscopic Studies ◽  
Lhc Ii ◽  
Ps Ii ◽  
Ps I ◽  
Pigment Protein Complexes

Biochemical and spectroscopic studies on the effects of high temperatures (45-47� C) over a 1 h period on the protein composition, fluorescence and photochemical activities of the barley thylakoid membrane were made. Photosystem II (PS II) activity decreased as expected, and photosystem I (PS I) activity also unexpectedly decreased. Our data support previous conclusions that the decrease in PS I activity is largely due to inactivation (or loss) of a component between the two photosystems. A two-dimensional electrophoretic system permitted first the separation of the thylakoid pigment-protein complexes of unstressed and stressed plants, followed by a determination of their subunit composition. The changes in the protein composition of each pigment-protein complex in response to elevated temperatures were monitored. Heat changed the quaternary structure of PS II and resulted in removal of the oxygen-evolving enhancer proteins from the thylakoid, but did essentially no damage to the PS I complex. The PS II core complex dissociated from a dimeric form to a monomeric one, and the major LHC II component (LHC IIb) changed from a trimeric to a monomeric form. The pigments that are lost from thylakoids during heat stress are mainly removed from the PS II pigment-proteins.

Herbicides which Interfere with the Biosynthesis of Carotenoids and Their Effect on Pigment Excitation, Chlorophyll Fluorescence and Pigment Composition of the Thylakoid Membrane

1984 ◽  
Vol 39 (5) ◽  
pp. 455-458 ◽  
Author(s):  
K. H. Grumbach
Keyword(s):  
Chlorophyll Fluorescence ◽  
Thylakoid Membrane ◽  
Protein Complexes ◽  
Red Light ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Pigment Composition ◽  
Fluorescence Emission Spectra ◽  
Characteristic Emission ◽  
Pigment Protein Complexes

Plants grown in the presence of the herbicides assayed synthesized chlorophylls during growth at low fluence rates. Subsequent irradiation with higher fluence rates of red light induced a strong chlorosis with SAN 6706 being a much stronger herbicide than J 852 or amino-triazole. All herbicides assayed also changed the content and composition of chlorophylls, carotenoids and pigment-protein-complexes of the thylakoid membrane and therefore the pigment excitation and chlorophyll fluorescence emission spectra of the plastid. With increasing herbicide toxicity the main characteristic emission bands at 690 and 730 nm disappeared and new emission bands at 715 (J 852) and 700 nm (SAN 6706) appeared. Such “artificial” membranes with a changed pigment composition were very susceptible to light. Presented data may be taken as evidence, that the lack of photoprotective cyclic carotenoids caused by the specific action of a bleaching herbicide is the primary event that may lead to a disturbed formation of the thylakoid membrane and its destruction by light and oxygen.

scholarly journals Fast Diffusion of the Unassembled PetC1-GFP Protein in the Cyanobacterial Thylakoid Membrane

Life ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 15
Author(s):  
Radek Kaňa ◽  
Gábor Steinbach ◽  
Roman Sobotka ◽  
György Vámosi ◽  
Josef Komenda
Keyword(s):  
Membrane Proteins ◽  
Single Molecule ◽  
Protein Interactions ◽  
Thylakoid Membrane ◽  
Protein Complexes ◽  
Correlation Spectroscopy ◽  
Membrane Microdomains ◽  
Fast Diffusion ◽  
Light Harvesting Complexes ◽  
Term Survival

Biological membranes were originally described as a fluid mosaic with uniform distribution of proteins and lipids. Later, heterogeneous membrane areas were found in many membrane systems including cyanobacterial thylakoids. In fact, cyanobacterial pigment–protein complexes (photosystems, phycobilisomes) form a heterogeneous mosaic of thylakoid membrane microdomains (MDs) restricting protein mobility. The trafficking of membrane proteins is one of the key factors for long-term survival under stress conditions, for instance during exposure to photoinhibitory light conditions. However, the mobility of unbound ‘free’ proteins in thylakoid membrane is poorly characterized. In this work, we assessed the maximal diffusional ability of a small, unbound thylakoid membrane protein by semi-single molecule FCS (fluorescence correlation spectroscopy) method in the cyanobacterium Synechocystis sp. PCC6803. We utilized a GFP-tagged variant of the cytochrome b6f subunit PetC1 (PetC1-GFP), which was not assembled in the b6f complex due to the presence of the tag. Subsequent FCS measurements have identified a very fast diffusion of the PetC1-GFP protein in the thylakoid membrane (D = 0.14 − 2.95 µm2s−1). This means that the mobility of PetC1-GFP was comparable with that of free lipids and was 50–500 times higher in comparison to the mobility of proteins (e.g., IsiA, LHCII—light-harvesting complexes of PSII) naturally associated with larger thylakoid membrane complexes like photosystems. Our results thus demonstrate the ability of free thylakoid-membrane proteins to move very fast, revealing the crucial role of protein–protein interactions in the mobility restrictions for large thylakoid protein complexes.

scholarly journals Discoloration of Historical Plastic Objects: New Insight into the Degradation of β-Naphthol Pigment Lakes

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2278
Author(s):  
Anna Micheluz ◽  
Eva Mariasole Angelin ◽  
João Almeida Lopes ◽  
Maria João Melo ◽  
Marisa Pamplona
Keyword(s):  
Light Exposure ◽  
Molecular Structures ◽  
Conservation Science ◽  
Organic Pigment ◽  
Organic Pigments ◽  
Before And After ◽  
The Individual ◽  
Determining Factor ◽  
Insight Into ◽  
Historical Samples

Light is a determining factor in the discoloration of plastics, and photodegradation processes can affect the molecular structures of both the polymer and colorants. Limited studies focused on the discoloration of heritage plastics in conservation science. This work investigated the discoloration of red historical polyethylene (PE) objects colored with PR 48:2 and PR 53:1. High-density and low-density PE reference polymers, neat pigment powders, and historical samples were assessed before and after accelerated photoaging. The applied methodology provided insight into the individual light-susceptibility of polyethylenes, organic pigment lakes, and their combined effect in the photoaging of historical plastic formulations. After light exposure, both PE references and historical samples yellowed, PR53:1 faded, and PR 48:2 darkened; however, both organic pigments faded severely in the historical samples. This highlights the role played by the plastic binder likely facilitating the pigment photofading. Fourier transform infrared spectroscopy and mass spectrometry techniques—EGA-MS, PY-GC/MS, and TD-GC/MS—were successfully employed for characterizing the plastic formulations and degradation. The identification of phthalic compounds in both aged β-naphthol powders opens new venues for studies on their degradation. This work’s approach and analytical methods in studying the discoloration of historical plastics are novel, proving their efficacy, reliability, and potentiality.

scholarly journals Two Sides of the Coin: Ezrin/Radixin/Moesin and Merlin Control Membrane Structure and Contact Inhibition

2019 ◽  
Vol 20 (8) ◽  
pp. 1996 ◽  
Author(s):  
Katharine A. Michie ◽  
Adam Bermeister ◽  
Neil O. Robertson ◽  
Sophia C. Goodchild ◽  
Paul M. G. Curmi
Keyword(s):  
Actin Cytoskeleton ◽  
Protein Complexes ◽  
Membrane Vesicle ◽  
Contact Inhibition ◽  
Cell Junctions ◽  
Cellular Membranes ◽  
Membrane Structures ◽  
Cortical Actin ◽  
Erm Proteins ◽  
Structural Conservation

The merlin-ERM (ezrin, radixin, moesin) family of proteins plays a central role in linking the cellular membranes to the cortical actin cytoskeleton. Merlin regulates contact inhibition and is an integral part of cell–cell junctions, while ERM proteins, ezrin, radixin and moesin, assist in the formation and maintenance of specialized plasma membrane structures and membrane vesicle structures. These two protein families share a common evolutionary history, having arisen and separated via gene duplication near the origin of metazoa. During approximately 0.5 billion years of evolution, the merlin and ERM family proteins have maintained both sequence and structural conservation to an extraordinary level. Comparing crystal structures of merlin-ERM proteins and their complexes, a picture emerges of the merlin-ERM proteins acting as switchable interaction hubs, assembling protein complexes on cellular membranes and linking them to the actin cytoskeleton. Given the high level of structural conservation between the merlin and ERM family proteins we speculate that they may function together.

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