Tailed Forisomes of Canavalia gladiata: A New Model to Study Ca2+-driven Protein Contractility
1 Indiana University/Purdue University, Department of Biology, 2101 East Coliseum Boulevard, Fort Wayne, IN 46805-1499, USA
2 School of Biological Science, Washington State University, Pullman, WA 99164-4236, USA
3 Department of Mechanical and Aerospace Engineering, Washington University, St Louis, MO 63130, USA
4 Institut für Allgemeine Botanik, Justus-Liebig-Universität, Senckenbergstr. 17–21, D-35390 Gießen, Germany
5 Department of Electrical and Systems Engineering, Washington University, St Louis, MO 63130, USA
* For correspondence. E-mail: petersw{at}ipfw.edu or knoblauch{at}wsu.edu
Received: 15 January 2007 Returned for revision: 25 February 2007 Accepted: 5 March 2007 Published electronically: 5 March 2007
Background and Aims: Forisomes are Ca2+-dependent contractile protein bodies that form reversible plugs in sieve tubes of faboid legumes. Previous work employed Vicia faba forisomes, a not entirely unproblematic experimental system. The aim of this study was to seek to establish a superior model to study these intriguing actuators.
Methods: Existing isolation procedures were modified to study the exceptionally large, tailed forisomes of Canavalia gladiata by differential interference contrast microscopy in vitro. To analyse contraction/expansion kinetics quantitatively, a geometric model was devised which enabled the computation of time-courses of derived parameters such as forisome volume from simple parameters readily determined on micrographs.
Key Results: Advantages of C. gladiata over previously utilized species include the enormous size of its forisomes (up to 55 µm long), the presence of tails which facilitate micromanipulation of individual forisomes, and the possibility of collecting material repeatedly from these fast-growing vines without sacrificing the plants. The main bodies of isolated Canavalia forisomes were box-shaped with square cross-sections and basically retained this shape in all stages of contraction. Ca2+-induced a 6-fold volume increase within about 10–15 s; the reverse reaction following Ca2+-depletion proceeded in a fraction of that time.
Conclusions: The sword bean C. gladiata provides a superior experimental system which will prove indispensable in physiological, biophysical, ultrastructural and molecular studies on the unique ATP-independent contractility of forisomes.
Key words: Ca2+-dependent contractility, contractile protein, fabaceae, forisome geometry, contraction kinetics, Canavalia gladiata, phloem transport, sieve element, tailed forisome
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  H. C. Pelissier, W. S. Peters, R. Collier, A. J. E. v. Bel, and M. Knoblauch GFP Tagging of Sieve Element Occlusion (SEO) Proteins Results in Green Fluorescent Forisomes Plant Cell Physiol., November 1, 2008; 49(11): 1699 - 1710. [Abstract] [Full Text] [PDF]
|
|