Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists watch cell-shape process for first time

11.10.2010
Researchers at the Carnegie Institution for Science, with colleagues at the Nara Institute of Science and Technology, observed for the first time a fundamental process of cellular organization in living plant cells: the birth of microtubules by studying recruitment and activity of individual protein complexes that create the cellular protein network known as the microtubule cytoskeleton—the scaffolding that provides structure and ultimately form and shape to the cell. These fundamental results could be important to agricultural research and are published in the October 10, 2010, early on-line edition of Nature Cell Biology.

All plant and animal cells rely on an elaborate array of molecular rods built from the protein tubulin. These rods, called microtubules, organize the cell and generate forces needed to support cell shape, cell movement, and importantly, cell division.

To perform these tasks, microtubules need to be organized into specific configurations. Animal cells separate their chromosomes during cell division by organizing the microtubules network from centrioles. A big mystery is how plants, which do not have centrioles organize their microtubule network. Understanding these mechanisms of molecular organization is a primary goal of cell biology.

As co-author David Ehrhardt from Carnegie's Department of Plant Biology explained: "In many cells, microtubule arrays are created with aid of a centralized body called a centrosome. Centrosomal arrays have been a focus of research for decades and much is now understood about how these arrays are created and organized by the centrosome. However, many differentiated animal cells, and flowering plant cells have arrays that are created independently of a centrosome. In fact, flowering plants lack centrosomes all together. Although these centrosome arrays are common in nature, they have received less study and their organization mechanisms remain largely mysterious."

The Ehrhardt lab previously found that individual microtubules in plant cell arrays are born at many locations along the inside of the cell membrane, where they are detached from the sites of birth and move along the membrane to interact with other microtubules. A primary challenge for investigating the molecular basis for these processes has been visualization of the protein complexes that give birth to new microtubule polymers.

The Ehrhardt and Hashimoto groups met this challenge by tagging a component of these complexes, known as nucleating complexes, with multiple copies of a fluorescent protein derived from jellyfish. When introduced into plant cells and visualized with highly sensitive spinning disk confocal microscopy, this tagged protein permitted the researchers to observe what happens as the microtubule array is being built.

Ehrhardt continued: "In centrosomal arrays, these nucleating complexes are recruited to the centrosome, where they give rise to a star-shaped array centered near the nucleus. By contrast, in the cells we studied these complexes were distributed at the cell membrane and were primarily located along the sides of other microtubules, an association that was correlated with their activity. So, microtubules appear to be important for locating and regulating their own formation proteins. In addition, daughter microtubules were created either at a distinct angle to the mother polymer, or in parallel to it. This choice of angle may play a role in either creating new organizational states or maintaining an existing one."

The investigators observed that formation complexes frequently did not remain in place after creating new microtubules, but often left, presumably to go through a new cycle of microtubule creation at a new location. The scientists hypothesized that liberation of the complexes from mother microtubules might be related to the mechanism of daughter microtubule detachment from origination sites.

To explore these questions, the investigators introduced their probe into a mutant lacking the protein katanin (named for a Japanese word for sword), whose job it is to cut microtubules into pieces. The scientists thought that katanin might be responsible for separating new microtubules from their formation complexes. In fact, without the cutting protein, the daughter microtubules completely failed to detach from their birth sites, and tagged formation complexes remained at the base of the daughter microtubule. The only time they saw a formation complex leave in the mutants was when the microtubule completely depolymerized—that is, the process whereby a large molecule decomposes into individual units. When this occurred, the tagged complex also disappeared. The results indicate that the formation complexes remain associated with mother microtubules until the daughter microtubule is removed either by katanin cutting or by complete depolymerization.

"As far as we are aware, this research is the first to witness the dynamics of individual gamma tubulin complex processes, which are fundamental to every plant and animal," remarked Ehrhardt. "We look at our plant system as a model for non-centrosomal array organization, which also occurs in many important differentiated animal cells. While we anticipate that some of the molecular players may be different, many of the principles may be similar. What we learn here could help us understand basic mechanisms underlying crop plant growth and development, and could have implications for understanding the process of acquiring cell shape and function of human cells."

*Authors on the paper are Masayoshi Nakamura of the Nara Institute of Science and Technology; David Ehrhardt of Carnegie; and Takashi Hashimoto of Nara and Stanford University. The work was partially supported by the Carnegie Institution for Science, the Japanese NARA Institute of Science and Technology and the Ministry of Education, Culture, Sports, Science and Technology.

The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

David Ehrhardt | EurekAlert!
Further information:
http://www.carnegiescience.edu

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>