|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | |||||
First published online March 2, 2004
doi: 10.1242/10.1242/jcs.00966
Research Article |
1 University of Fribourg, Biology Department, Plant Biology, Fribourg, Switzerland
2 University of Zürich, Institute of Plant Biology, Zürich Switzerland
* Author for correspondence (e-mail: ulrich.ryser{at}unifr.ch)
Accepted 4 November 2003
The water pipes of elongating plant organs are the result of programmed cell death and are formed by the walls of dead and empty protoxylem elements. These protoxylem elements are passively elongated many times by the surrounding tissue before they are replaced and collapse. Well-known adaptations for this unique task include the characteristic secondary wall thickenings, forming rings and helices. A new, clearly distinct structural element containing glycine-rich proteins is now visualized for the first time, using confocal laser scanning microscopy in the mature protoxylem of elongating organs of seed plants. This structural element is arranged along the longitudinal axis of the protoxylem elements. It interconnects the secondary wall thickenings within and between protoxylem elements, as well as the protoxylem with other cell types such as xylem parenchyma cells and metaxylem elements. The structural element is stable against detergent extractions, proteinase, pectinase and cellulase hydrolysis, and is closely associated with rhamnogalacturonan-I, a pectic polysaccharide. The results clearly demonstrate that the cell wall of protoxylem cells is a highly dynamic and complex structure. The typical polysaccharide-rich primary wall of living and elongating plant cells is progressively modified and finally replaced by a protein-rich wall in the dead and passively stretched protoxylem elements. These glycine-rich walls originated early in the evolution of the seed plants as confirmed by the analysis of genomic information.
Key words: Extracellular matrix, Glycine-rich cell-wall protein, Plant anatomy, Protoxylem, Rhamnogalacturonan I, Seed plants (spermatophytes)
![]()
CiteULike
Complore
Connotea
Del.icio.us
Digg
Reddit
Technorati
Twitter What's this?
Related articles in JCS: