scholarly journals Genome communication in plants mediated by organelle–n­ucleus-located proteins

2020 ◽  
Vol 375 (1801) ◽  
pp. 20190397 ◽  
Author(s):  
Karin Krupinska ◽  
Nicolás E. Blanco ◽  
Svenja Oetke ◽  
Michela Zottini
Keyword(s):  
Chloroplast Development ◽  
Cell Cycle Control ◽  
Plastid Transformation ◽  
Light Responses ◽  
Dual Targeting ◽  
Dual Localization ◽  
Retrograde Signalling ◽  
Eukaryotic Proteins ◽  
Plastid Proteins ◽  
Associated Proteins

An increasing number of eukaryotic proteins have been shown to have a dual localization in the DNA-containing organelles, mitochondria and plastids, and/or the nucleus. Regulation of dual targeting and relocation of proteins from organelles to the nucleus offer the most direct means for communication between organelles as well as organelles and nucleus. Most of the mitochondrial proteins of animals have functions in DNA repair and gene expression by modelling of nucleoid architecture and/or chromatin. In plants, such proteins can affect replication and early development. Most plastid proteins with a confirmed or predicted second location in the nucleus are associated with the prokaryotic core RNA polymerase and are required for chloroplast development and light responses. Few plastid–nucleus-located proteins are involved in pathogen defence and cell cycle control. For three proteins, it has been clearly shown that they are first targeted to the organelle and then relocated to the nucleus, i.e. the nucleoid-associated proteins HEMERA and Whirly1 and the stroma-located defence protein NRIP1. Relocation to the nucleus can be experimentally demonstrated by plastid transformation leading to the synthesis of proteins with a tag that enables their detection in the nucleus or by fusions with fluoroproteins in different experimental set-ups. This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’.

scholarly journals Evidence for dual targeting of Arabidopsis plastidial glucose-6-phosphate transporter GPT1 to peroxisomes via the ER

2019 ◽  
Author(s):  
Marie-Christin Baune ◽  
Hannes Lansing ◽  
Kerstin Fischer ◽  
Tanja Meyer ◽  
Lennart Charton ◽  
...  
Keyword(s):  
Seed Set ◽  
Embryo Sac ◽  
Transit Peptide ◽  
Pentose Phosphate ◽  
Peroxisomal Membrane ◽  
On Demand ◽  
Dual Targeting ◽  
Phosphate Translocator ◽  
Dual Localization ◽  
Essential Function

ABSTRACTFormer studies on Arabidopsis glucose-6-phosphate/phosphate translocator isoforms GPT1 and GPT2 reported viability of gpt2 mutants, however an essential function for GPT1, manifesting as a variety of gpt1 defects in the heterozygous state during fertilization/seed set. Among other functions, GPT1 is important for pollen and embryo-sac development. Since previous work on enzymes of the oxidative pentose phosphate pathway (OPPP) revealed comparable effects, we investigated whether GPT1 might dually localize to plastids and peroxisomes. In reporter fusions, GPT2 was found at plastids, but GPT1 also at the endoplasmic reticulum (ER) and around peroxisomes. GPT1 contacted oxidoreductases and also peroxins that mediate import of peroxisomal membrane proteins from the ER, hinting at dual localization. Reconstitution in yeast proteoliposomes revealed that GPT1 preferentially exchanges glucose-6-phosphate for ribulose-5-phosphate. Complementation analyses of heterozygous gpt1 plants demonstrated that GPT2 is unable to compensate for GPT1 in plastids, whereas genomic GPT1 without transit peptide (enforcing ER/peroxisomal localization) increased gpt1 transmission significantly. Since OPPP activity in peroxisomes is essential during fertilization, and immuno-blot analyses hinted at unprocessed GPT1-specific bands, our findings suggest that GPT1 is indispensable at both plastids and peroxisomes. Together with the G6P-Ru5P exchange preference, dual targeting explains why GPT1 exerts functions distinct from GPT2 in Arabidopsis.One sentence summaryIn contrast to plastidial GPT2, GPT1 exhibits slightly different exchange preferences and alternatively targets the ER, from where the protein can be relocated to peroxisomes on demand.

scholarly journals An isoform of the plastid RNA polymerase-associated protein FSD3 negatively regulates chloroplast development

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Sangyool Lee ◽  
Young Hee Joung ◽  
Ju-Kon Kim ◽  
Yang Do Choi ◽  
Geupil Jang
Keyword(s):  
Rna Polymerase ◽  
Photosynthetic Activity ◽  
Chloroplast Development ◽  
Transmembrane Domain ◽  
Developmental Defects ◽  
Expression Of Genes ◽  
Associated Proteins ◽  
Plastid Rna Polymerase ◽  
Chloroplast Nucleoid

Abstract Background Plastid-encoded RNA polymerase (PEP) plays an essential role in chloroplast development by governing the expression of genes involved in photosynthesis. At least 12 PEP-associated proteins (PAPs), including FSD3/PAP4, regulate PEP activity and chloroplast development by modulating formation of the PEP complex. Results In this study, we identified FSD3S, a splicing variant of FSD3; the FSD3 and FSD3S transcripts encode proteins with identical N-termini, but different C-termini. Characterization of FSD3 and FSD3S proteins showed that the C-terminal region of FSD3S contains a transmembrane domain, which promotes FSD3S localization to the chloroplast membrane but not to nucleoids, in contrast to FSD3, which localizes to the chloroplast nucleoid. We also found that overexpression of FSD3S negatively affects photosynthetic activity and chloroplast development by reducing expression of genes involved in photosynthesis. In addition, FSD3S failed to complement the chloroplast developmental defects in the fsd3 mutant. Conclusion These results suggest FSD3 and FSD3S, with their distinct localization patterns, have different functions in chloroplast development, and FSD3S negatively regulates expression of PEP-dependent chloroplast genes, and development of chloroplasts.

scholarly journals JADE family proteins regulate proteasome abundance and activity

2021 ◽  
Author(s):  
Lena Kathrin Ebert ◽  
Sebastian Bargfrede ◽  
Katrin Bohl ◽  
Roman-Ulrich Mueller ◽  
Thomas Benzing ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Sequence Similarity ◽  
Genetic Disorders ◽  
Cell Cycle Control ◽  
26S Proteasome ◽  
Cellular Functions ◽  
Histone Acetyl Transferase ◽  
Direct Role ◽  
Associated Proteins ◽  
Almost All

JADE family proteins (JADE1/2/3) have been implicated in diverse cellular functions and signaling pathways ranging from WNT signaling and cell cycle control to cell death and complex transcriptional regulation through histone acetyl-transferase complexes. JADE proteins show a high degree of sequence similarity and share two PHD zinc finger domains. JADE1 interacts with cilia-associated proteins and has been implicated in cilia-related genetic disorders with kidney phenotypes. However, the function of the widely expressed JADE proteins at the molecular level is still elusive. Here we show that JADE proteins regulate proteasome abundance and activity. Using kidney cells as a model, we demonstrate that loss of either JADE protein resulted in increased expression of almost all components of the 26S proteasome. Regulation occurred at the post-translational level and was not the consequence of transcriptional activation. Consistent with a role for JADE proteins in regulating overall proteasomal abundance, proteasomal activity was elevated in Jade-deficient cells, while exogenous expression of JADE1/2/3 decreased the level of proteasome activity. Coimmunoprecipitation experiments confirmed the interaction of proteasomal subunits with Jade1 suggesting a direct role of JADE proteins in regulating turnover, stability and abundance of the 26s proteasome. These data may now explain the plethora of cellular roles that have been attributed to JADE proteins.

Photoreceptor disk membrane substructures by means of the complementary freeze-fracture-replica methods

1978 ◽  
Vol 36 (2) ◽  
pp. 156-157
Author(s):  
A. Tonosaki ◽  
M. Yamasaki ◽  
H. Washioka ◽  
J. Mizoguchi
Keyword(s):  
Cell Membranes ◽  
Freeze Fracture ◽  
Purple Membrane ◽  
Remarkable Case ◽  
Single Face ◽  
Disk Membrane ◽  
Associated Proteins ◽  
Photoreceptor Membranes

A vertebrate disk membrane is composed of 40 % lipids and 60 % proteins. Its fracture faces have been classed into the plasmic (PF) and exoplasmic faces (EF), complementary with each other, like those of most other types of cell membranes. The hypothesis assuming the PF particles as representing membrane-associated proteins has been challenged by serious questions if they in fact emerge from the crystalline formation or decoration effects during freezing and shadowing processes. This problem seems to be yet unanswered, despite the remarkable case of the purple membrane of Halobacterium, partly because most observations have been made on the replicas from a single face of specimen, and partly because, in the case of photoreceptor membranes, the conformation of a rhodopsin and its relatives remains yet uncertain. The former defect seems to be partially fulfilled with complementary replica methods.

Characterization of microtubules by dark-field STEM and replication

1991 ◽  
Vol 49 ◽  
pp. 152-153
Author(s):  
S.B. Andrews ◽  
R.D. Leapman ◽  
P.E. Gallant ◽  
T.S. Reese
Keyword(s):  
Protein Interactions ◽  
Low Dose ◽  
Unit Length ◽  
Dark Field ◽  
Carbon Films ◽  
Microtubule Associated Proteins ◽  
Molecular Weights ◽  
Freeze Dried ◽  
Protein Motors ◽  
Associated Proteins

As part of a study on protein interactions involved in microtubule (MT)-based transport, we used the VG HB501 field-emission STEM to obtain low-dose dark-field mass maps of isolated, taxol-stabilized MTs and correlated these micrographs with detailed stereo images from replicas of the same MTs. This approach promises to be useful for determining how protein motors interact with MTs. MTs prepared from bovine and squid brain tubulin were purified and free from microtubule-associated proteins (MAPs). These MTs (0.1-1 mg/ml tubulin) were adsorbed to 3-nm evaporated carbon films supported over Formvar nets on 600-m copper grids. Following adsorption, the grids were washed twice in buffer and then in either distilled water or in isotonic or hypotonic ammonium acetate, blotted, and plunge-frozen in ethane/propane cryogen (ca. -185 C). After cryotransfer into the STEM, specimens were freeze-dried and recooled to ca.-160 C for low-dose (<3000 e/nm2) dark-field mapping. The molecular weights per unit length of MT were determined relative to tobacco mosaic virus standards from elastic scattering intensities. Parallel grids were freeze-dried and rotary shadowed with Pt/C at 14°.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

Alzheimer's Paired Helical Filaments Contain Insoluble Cytoskeletal Elements

1985 ◽  
Vol 43 ◽  
pp. 748-751
Author(s):  
P. Gambetti ◽  
G. Perry ◽  
L. Autillo-Gambetti
Keyword(s):  
Paired Helical Filaments ◽  
Microscope Level ◽  
Antigenic Determinants ◽  
Light Microscope Level ◽  
Neuronal Cytoskeleton ◽  
Ionic Detergent ◽  
Associated Proteins ◽  
Pathologic Lesions ◽  
10 Nm Filaments ◽  
Cytoskeletal Elements

Neurofibrillary tangles (NFT) are one of the major pathologic lesions of Alzheimer's disease. These neuronal inclusions are predominantly composed of paired helical filaments (PHF), which consist of two 10 nm filaments winding around each other with an approximately 80 nm periodicity. Besides PHF, NFT comprise also 15 nm filaments, 10 nm filaments which are probably neurofilaments, microtubules and granular material. At variance with the neuronal cytoskeleton, PHF are insoluble in ionic detergent.Studies at the light microscope level have shown that NFT have unique antigenic determinants as well as determinants in common with elements of the normal neuronal cytoskeleton such as neurofilaments and microtubule-associated proteins. The present study uses immunocytochemistry and cytochemistry at the electron microscope level to assess which NFT component contains these determinants and whether these antigenic determinants are soluble in an ionic detergent.

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