Information about Plasmodesma
Plasmodesmata (singular, plasmodesma) are microscopic channels of plants traversing the cell walls and middle lamella between pairs of plant cells and facilitating transport and communication between them. Unlike animal cells, plant cells are protected by a cell wall that is impermeable to large molecules such as proteins and in these cells plasmodesmata enable regulated intercellular transport. Plant cells can use both passive and active transport to move molecules and ions through the passage . A plasmodesma is constructed of three main layers, the plasma membrane, the cytoplasmic sleeve, and the desmotubule .
Around the desmotubule and the plasmamembrane areas of an electron dense material have been seen, often joined together by spoke-like structures that seem to split the plasmodesma into smaller channels . These structures may be composed of myosin and actin, which are part of the cell's cystoskeleton. If this is the case these proteins could be used in the selective transport of large molecules between the two cells.
Plasmodesmata have been shown to transport proteins, messenger RNA and viral genomes from cell to cell . The best studied of these are viral movement proteins such as those of the tobacco mosaic virus MP-30 . MP-30 is thought to bind to the virus's own genome and shuttle it from infected cells to uninfected cells through plasmodesmata. Flowering Locus T protein moves from leaves to the shoot apical meristem through plasmodesmata to initiate flowering.
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
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Structure
Plasmodesmal plasma membrane
The plasma membrane portion of the plasmodesma is a continuous extension of the cellular plasmalemma . It is similar in structure to most cellular phospholipid bilayers.Cytoplasmic sleeve
The cytoplasmic sleeve is enclosed by the plasma membrane and is an extension of the cytosol. Trafficking through plasmodesmata is assumed to occur through this passage. Smaller molecules (e.g. monosaccharides) and ions can easily pass through plasmodesmata by diffusion without the need for additional chemical energy. It is unknown how the selective transport of larger molecules, such as proteins, occurs. One hypothesis is that the polysaccharide callose accumulates around the neck region of plasmodesmata reducing their diameter and thereby controlling permeability to substances in the cytoplasm .Desmotubule
The desmotubule is a tube of appressed endoplasmic reticulum that runs between two adjacent cells . Some molecules are known to be transported through this channel , but it is not thought to be the main route for plasmodesmatal transport.Around the desmotubule and the plasmamembrane areas of an electron dense material have been seen, often joined together by spoke-like structures that seem to split the plasmodesma into smaller channels . These structures may be composed of myosin and actin, which are part of the cell's cystoskeleton. If this is the case these proteins could be used in the selective transport of large molecules between the two cells.
Transport
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Tobacco mosaic virus movement protein 30 localizes to plasmodesmata.
Links
Video showing vesicular transport through the plasmodesmata of a Water Lily petal cell. Kinesin and Dynein actively move the vesicles along microtubule highways, into and out of the cell. [1]References
Plantae
Haeckel, 1866[1]
Divisions
Green algae
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Haeckel, 1866[1]
Divisions
Green algae
- Chlorophyta
- Charophyta
- Non-vascular land plants (bryophytes)
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cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell.
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Plant cells are quite different from the cells of the other eukaryotic kingdoms' organisms. Their distinctive features include:
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- A large central vacuole (enclosed by a membrane, the tonoplast
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Plant cells are quite different from the cells of the other eukaryotic kingdoms' organisms. Their distinctive features include:
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- A large central vacuole (enclosed by a membrane, the tonoplast
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cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell.
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Active transport (sometimes called active uptake) is the mediated transport of biochemicals, and other atomic/molecular substances, across membranes. Unlike passive transport, this process requires the expenditure of cellular energy to move molecules "uphill" against a
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lipid bilayer or bilayer lipid membrane (BLM) is a membrane or zone of a membrane composed of lipid molecules (usually phospholipids). The lipid bilayer is a critical component of all biological membranes, including cell membranes, and so is absolutely essential for all
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The cytosol (cf. cytoplasm, which also includes the organelles) is the internal fluid of the cell, and a portion of cell metabolism occurs here. Proteins within the cytosol play an important role in signal transduction pathways and glycolysis.
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- This article is about the physical mechanism of diffusion. For alternative meanings, see diffusion (disambiguation).
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
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Callose is a plant polysaccharide. It is comprised of glucose residues linked together through b-1,3-linkages, and is termed a B-glucan. It is thought to be manufactured at the cell wall by callose synthases and is degraded by b-1,3-glucanases.
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Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility.
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Structure and Function
Domains
Most myosin molecules are composed of both a head and a tail domain...... Click the link for more information.
Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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Movement proteins are non-structural proteins encoded by many, if not all, plant viruses to enable their movement from one infected cell to neighbouring cells. Some plant viruses express more than one movement protein.
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Kinesins are a class of motor proteins found in cells. They are dimers (molecule pairs) reminiscent of feet on a rod. Kinesins move on the much larger microtubule cables powerered by the hydrolysis of ATP.
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Dynein is a motor protein (also called molecular motor or motor molecule) in cells which converts the chemical energy contained in ATP into the mechanical energy of movement.
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Vesicle may refer to
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- Vesicle (biology), a relatively small and enclosed compartment within a cell
- Vesicular texture, a small enclosed cavity found in some volcanic rock, such as basalt
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Microtubules are one of the components of the cytoskeleton. They have diameter of ~ 24 nm and length varying from several micrometers to possibly millimeters in axons of nerve cells.
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