Structure and function of plasmodesmata

2001 ◽  
Vol 28 (7) ◽  
pp. 711
Author(s):  
Leila M. Blackman ◽  
Robyn L. Overall
Keyword(s):  
Structure And Function ◽  
Passive Movement ◽  
Size Exclusion ◽  
Molecular Architecture ◽  
Exclusion Limit ◽  
Dynamic Nature ◽  
Cell Transport ◽  
Selective Transport ◽  
Size Exclusion Limit ◽  
And Function

Little is known about the molecular architecture of plasmodesmata. Electron micrographs of plasmodesmata, although showing remarkably consistent features, do not reveal the dynamic nature of plasmodesmata. In addition, the generally accepted size exclusion limit of plasmodesmata of 1 kDa as determined by the microinjection of fluorescent probes, is not an accurate measure of the size of molecules that can move from cell to cell. In some cases, plasmodesmata allow the non-selective movement of proteins up to 50 kDa, whereas others allow the selective transport of proteins such as transcription factors. Insights to the molecular architecture of plasmodesmata and the mechanism of cell-to-cell transport can be gained by the examination of the type of molecules and conditions under which selective and passive movement of molecules occurs.

Identification of a developmental transition in plasmodesmatal function during embryogenesis in Arabidopsis thaliana

Development ◽  
2002 ◽  
Vol 129 (5) ◽  
pp. 1261-1272 ◽  
Author(s):  
Insoon Kim ◽  
Frederick D. Hempel ◽  
Kyle Sha ◽  
Jennifer Pfluger ◽  
Patricia C. Zambryski
Keyword(s):  
Size Exclusion ◽  
Nutrient Transfer ◽  
Intercellular Signaling ◽  
Wild Type ◽  
Exclusion Limit ◽  
Fluorescent Tracer ◽  
Cell Transport ◽  
Developmental Transition ◽  
Size Exclusion Limit ◽  
Chromosome I

Plasmodesmata provide routes for communication and nutrient transfer between plant cells by interconnecting the cytoplasm of adjacent cells. A simple fluorescent tracer loading assay was developed to monitor patterns of cell-to-cell transport via plasmodesmata specifically during embryogenesis. A developmental transition in plasmodesmatal size exclusion limit was found to occur at the torpedo stage of embryogenesis in Arabidopsis; at this time, plasmodesmata are down-regulated, allowing transport of small (approx. 0.5 kDa) but not large (approx. 10 kDa) tracers. This assay system was used to screen for embryo-defective mutants, designated increased size exclusion limit of plasmodesmata(ise), that maintain dilated plasmodesmata at the torpedo stage. The morphology of ise1 and ise2 mutants discussed here resembled that of the wild-type during embryo development, although the rate of their embryogenesis was slower. The ISE1 gene was mapped to position 13 cM on chromosome I using PCR-based biallelic markers. ise2 was found to be allelic to the previously characterized mutant emb25 which maps to position 100 cM on chromosome I. The results presented have implications for intercellular signaling pathways that regulate embryonic development, and furthermore represent the first attempt to screen directly for mutants of Arabidopsis with altered size exclusion limit of plasmodesmata.

A urea channel from Bacillus cereus reveals a novel hexameric structure

2012 ◽  
Vol 445 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Gerard H. M. Huysmans ◽  
Nathan Chan ◽  
Jocelyn M. Baldwin ◽  
Vincent L. G. Postis ◽  
Svetomir B. Tzokov ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Structure And Function ◽  
Size Exclusion ◽  
Fluorescent Labelling ◽  
Transmembrane Helices ◽  
Cryo Electron Microscopy ◽  
C Terminus ◽  
Exclusion Chromatography ◽  
Urea Channel ◽  
And Function

Urea is exploited as a nitrogen source by bacteria, and its breakdown products, ammonia and bicarbonate, are employed to counteract stomach acidity in pathogens such as Helicobacter pylori. Uptake in the latter is mediated by UreI, a UAC (urea amide channel) family member. In the present paper, we describe the structure and function of UACBc, a homologue from Bacillus cereus. The purified channel was found to be permeable not only to urea, but also to other small amides. CD and IR spectroscopy revealed a structure comprising mainly α-helices, oriented approximately perpendicular to the membrane. Consistent with this finding, site-directed fluorescent labelling indicated the presence of seven TM (transmembrane) helices, with a cytoplasmic C-terminus. In detergent, UACBc exists largely as a hexamer, as demonstrated by both cross-linking and size-exclusion chromatography. A 9 Å (1 Å=0.1 nm) resolution projection map obtained by cryo-electron microscopy of two-dimensional crystals shows that the six protomers are arranged in a planar hexameric ring. Each exhibits six density features attributable to TM helices, surrounding a putative central channel, while an additional helix is peripherally located. Bioinformatic analyses allowed individual TM regions to be tentatively assigned to the density features, with the resultant model enabling identification of residues likely to contribute to channel function.

Abstract 15070: Micu1 Regulates Mitochondrial Cristae Structure and Function Independent of the Mitochondrial Calcium Uniporter Channel

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Dhanendra Tomar ◽  
Manfred Thomas ◽  
Joanne Garbincius ◽  
Devin Kolmetzky ◽  
Oniel Salik ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Coiled Coil ◽  
Structure And Function ◽  
Membrane Dynamics ◽  
Size Exclusion ◽  
Null Mouse ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Cytochrome C Release ◽  
And Function

Background: MICU1 is an EF-hand domain containing Ca 2+ -sensor regulating the mitochondrial Ca 2+ uniporter channel and mitochondrial Ca 2+ uptake. MICU1-null mouse and fly models display perinatal lethality with disorganized mitochondrial architecture. Interestingly, these phenotypes are distinct from other mtCU loss-of-function models ( MCU, MICU2, EMRE, MCUR1 ) and thus are likely not explained solely by changes in matrix Ca 2+ content. Using size-exclusion proteomics and co-immunofluorescence, we found that MICU1 localizes to mitochondrial complexes lacking MCU. These observations suggest that MICU1 may have additional cellular functions independent of the MCU. Methods: Biotin-based proximity labeling and proteomics, protein biochemistry, live-cell Ca 2+ imaging, electron microscopy, confocal and super-resolution imaging were utilized to identify and validate MICU1 novel functions. Results: The expression of a MICU1-BioID2 fusion protein in MCU +/+ and MCU -/- cells allowed the identification of the total vs. MCU-independent MICU1 interactome. LC-MS analysis of purified biotinylated proteins identified the mitochondrial contact site and cristae organizing system (MICOS) components Mitofilin (MIC60) and Coiled-coil-helix-coiled-coil helix domain containing 2 (CHCHD2) as MCU independent novel MICU1 interactors. We demonstrate that MICU1 is essential for proper organization of the MICOS complex and that MICU1 ablation results in altered cristae organization, mitochondrial ultrastructure, mitochondrial membrane dynamics, membrane potential, and cell death signaling. We hypothesize that MICU1 is a MICOS Ca 2+ - sensor since perturbing MICU1 is sufficient to modulate cytochrome c release independent of Ca 2+ uptake across the inner mitochondrial membrane. Conclusions: Here, we provide the first experimental evidence of an intermembrane space Ca 2+ - sensor regulating mitochondrial membrane dynamics, independent of changes in matrix Ca 2+ content. This study provides a novel paradigm to understand Ca 2+ -dependent regulation of mitochondrial structure and function and may help explain the mitochondrial remodeling reported to occur in numerous disease states.

The chloroplastic DEVH-box RNA helicase INCREASED SIZE EXCLUSION LIMIT 2 involved in plasmodesmata regulation is required for group II intron splicing

2015 ◽  
Vol 39 (1) ◽  
pp. 165-173 ◽  
Author(s):  
Nicolas Carlotto ◽  
Sonia Wirth ◽  
Nicolas Furman ◽  
Nazarena Ferreyra Solari ◽  
Federico Ariel ◽  
...  
Keyword(s):  
Group Ii Intron ◽  
Rna Helicase ◽  
Size Exclusion ◽  
Intron Splicing ◽  
Exclusion Limit ◽  
Size Exclusion Limit ◽  
Group Ii

Movement Protein of Tobacco Mosaic Virus Modifies Plasmodesmatal Size Exclusion Limit

Science ◽  
1989 ◽  
Vol 246 (4928) ◽  
pp. 377-379 ◽  
Author(s):  
S. WOLF ◽  
W. J. LUCAS ◽  
C. M. DEOM ◽  
R. N. BEACHY
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Movement Protein ◽  
Size Exclusion ◽  
Exclusion Limit ◽  
Size Exclusion Limit

scholarly journals Him-10 Is Required for Kinetochore Structure and Function on Caenorhabditis elegans Holocentric Chromosomes

2001 ◽  
Vol 153 (6) ◽  
pp. 1227-1238 ◽  
Author(s):  
Mary Howe ◽  
Kent L. McDonald ◽  
Donna G. Albertson ◽  
Barbara J. Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Structure And Function ◽  
Holocentric Chromosomes ◽  
Molecular Architecture ◽  
Mitotic Chromosomes ◽  
C Elegans ◽  
Meiotic Chromosomes ◽  
Evolutionarily Conserved ◽  
And Function ◽  
Chromosome Nondisjunction

Macromolecular structures called kinetochores attach and move chromosomes within the spindle during chromosome segregation. Using electron microscopy, we identified a structure on the holocentric mitotic and meiotic chromosomes of Caenorhabditis elegans that resembles the mammalian kinetochore. This structure faces the poles on mitotic chromosomes but encircles meiotic chromosomes. Worm kinetochores require the evolutionarily conserved HIM-10 protein for their structure and function. HIM-10 localizes to the kinetochores and mediates attachment of chromosomes to the spindle. Depletion of HIM-10 disrupts kinetochore structure, causes a failure of bipolar spindle attachment, and results in chromosome nondisjunction. HIM-10 is related to the Nuf2 kinetochore proteins conserved from yeast to humans. Thus, the extended kinetochores characteristic of C. elegans holocentric chromosomes provide a guide to the structure, molecular architecture, and function of conventional kinetochores.

scholarly journals Determining the Size Exclusion for Nanoparticles in Citrus Leaves

HortScience ◽  
2016 ◽  
Vol 51 (6) ◽  
pp. 732-737 ◽  
Author(s):  
Ed Etxeberria ◽  
Pedro Gonzalez ◽  
Priyanka Bhattacharya ◽  
Parvesh Sharma ◽  
Pu Chun Ke
Keyword(s):  
Cell Wall ◽  
Plant Cell Wall ◽  
Fluorescent Microscopy ◽  
Leaf Tissue ◽  
Porous Matrix ◽  
Pamam Dendrimers ◽  
Size Exclusion ◽  
Exclusion Limit ◽  
Size Exclusion Limit ◽  
Citrus Leaves

Implementation of nanotechnology in agriculture is intimately dependent on the capacity of nanoparticles (NPs) to move within the plant body and reach the targeted cells. Although the fibrillar nature of the plant cell wall permits the movement of molecules through its porous matrix (apoplast), the movement of particles through the aqueous apoplastic milieu has its size limitations given the tightly knitted cellulose/hemicellulose fiber structure. In the present study, we used fluorescent NPs of different composition and sizes, and followed their movement into citrus leaves by fluorescent microscopy. Our results indicate that in citrus leaves, the size exclusion limit for NPs is of ≈5.4 nm. This conclusion was based on the capacity of PAMAM dendrimers G-4 and G-5 (4.5 and 5.4 nm, respectively) to move through the cell wall and into the phloem, but failure of similar PAMAM dendrimers G-6 (6.7 nm) to move through the apoplast. Dendrimer NPs 5.4 nm and smaller were observed to penetrate the leaf tissue, and then taken up and mobilized by the phloem elements. The current study provides evidence on the size limit for NPs use in agriculture.

scholarly journals Cucumber Mosaic Virus Movement Protein Severs Actin Filaments to Increase the Plasmodesmal Size Exclusion Limit in Tobacco

2010 ◽  
Vol 22 (4) ◽  
pp. 1373-1387 ◽  
Author(s):  
Shengzhong Su ◽  
Zhaohui Liu ◽  
Cheng Chen ◽  
Yan Zhang ◽  
Xu Wang ◽  
...  
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Actin Filaments ◽  
Movement Protein ◽  
Size Exclusion ◽  
Virus Movement ◽  
Exclusion Limit ◽  
Size Exclusion Limit
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