Cytoskeleton

(Click image to enlarge in new window)

After a day on the beach, I grew so tired of the heat that I decided to travel to somewhere cool… actually, somewhere cold: a ski resort. Today I can see that there are just as many people on the ski resort as the beach. My search will be no easier, but at least I do not have to squeeze between sweaty bodies.  I am determined to find the next organelle, the cytoskeleton, which I hear appears like a thin network of strings. Can you find it before I do?

<Scroll to bottom for correct location…>

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Structure

A plant’s cytoskeleton extends throughout its whole cytoplasm. Its two major components are microtubules and actin microfilaments. Microtubules are formed by the centrosome, or the microtubule organizing center, which differs from that of an animal cell because it does not include centrioles.

  • Microtubules: a hollow tube made of 13 strands of tubulin dimers. Measures 25nm in diameter.
  • Microfilaments: a long polymer fiber made of two actin strands. Measures 7nm in diameter.

Plant cells do not depend on intermediate filaments like animal cells because the cell wall already stabilizes cell shape. Intermediate filaments are generally needed to anchor organelles and maintain structure.

The cytoskeleton is not easily visible–not with a light microscope and certainly not with the naked eye–but techniques such as confocal microscopy with treatments of taxol, oryzalin, and NPA can produce clear images. The examples below are from a project at UCS (the University of Louisiana at Lafayette).

Cytoskeleton of taxol-treated plant roots

Rhodamine-phalloidin stained f-actin in corn root

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Function

The cytoskeleton primarily provides structural support to the cell; microtubules resist compression and microfilaments resist tension. In addition to strengthening the internal structure, the cytoskeleton also regulates cell growth, development, and division. For instance, the centrosome produces microtubules that stretch across the cell during the prophase of mitosis. These microtubules help split the chromosomes and arrange the division of the cell plate. Actin microfilaments may also guide vesicles and other organelles to move to their correct locations. Because the cytoskeleton is a system that encompasses a multitude of other organelles, it is still under in-depth investigation by researchers and scientists. There is still much to discover about the method by which the cytoskeleton contributes to cell growth and development, and new findings reveal a greater variety of roles of this complex filament network.

Microtubules in cell division (http://www.ncbi.nlm.nih.gov/books/NBK26831/)

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