JXB Advance Access first published online on July 5, 2007
This version published online on July 19, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm143
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
Ca2+-mediated remote control of reversible sieve tube occlusion in Vicia faba
1Plant Cell Biology Research Group, Institute of General Botany, Justus-Liebig-University, Senckenbergstrasse 17, D-35390 Giessen, Germany
2Department of Plant Biology, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark
* To whom correspondence should be addressed. E-mail: aart.v.bel{at}bot1.bio.uni-giessen.de
According to an established concept, injury of the phloem triggers local sieve plate occlusion including callose-mediated constriction and, possibly, protein plugging of the sieve pores. Sieve plate occlusion can also be achieved by distant stimuli, depends on the passage of electropotential waves (EPWs), and is reversible in intact plants. The time-course of the wound response was studied in sieve elements of main veins of intact Vicia faba plants using confocal and multiphoton microscopy. Only 15–45 s after burning a leaf tip, forisomes (giant protein bodies specific for legume sieve tubes) suddenly dispersed, as observed at 3–4 cm from the stimulus site. The dispersion was reversible; the forisomes had fully re-contracted 7–15 min after burning. Meanwhile, callose appeared at the sieve pores in response to the heat shock. Callose production reached a maximum after 
20 min and was also reversible; callose degraded over the subsequent 1–2 h. The heat induction of both modes of occlusion coincided with the passage of an EPW visualized by electrophysiology or the potential-sensitive dye RH-414. In contrast to burning, cutting of the leaf tip induced neither an EPW nor callose deposition. The data are consistent with a remote-controlled occlusion of sieve plates depending on the longitudinal propagation of an EPW releasing Ca2+ into the sieve element lumen. It is hypothesized that forisome plugs and callose constriction are removed once the cytosolic calcium level has returned to the initial level in those sieve tubes.
Key words: Callose, CLSM, forisome, membrane potential, phloem, Vicia faba
This is a new version as the first version of the article was not Open Access.
Received 16 April 2007; Revised 29 May 2007 Accepted 30 May 2007
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