AOBPreview published online on October 4, 2007
Annals of Botany, doi:10.1093/aob/mcm248
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Xyloglucan Endotransglucosylase Activity Loosens a Plant Cell Wall
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University of Antwerpen, Biology Department, Groenenborgerlaan 171, 2020 Antwerpen, Belgium
* For correspondence. E-mail kris.vissenberg{at}ua.ac.be
Received: 6 June 2007 Returned for revision: 10 August 2007 Accepted: 14 August 2007
Background and Aims: Plant cells undergo cell expansion when a temporary imbalance between the hydraulic pressure of the vacuole and the extensibility of the cell wall makes the cell volume increase dramatically. The primary cell walls of most seed plants consist of cellulose microfibrils tethered mainly by xyloglucans and embedded in a highly hydrated pectin matrix. During cell expansion the wall stress is decreased by the highly controlled rearrangement of the load-bearing tethers in the wall so that the microfibrils can move relative to each other. Here the effect was studied of a purified recombinant xyloglucan endotransglucosylase/hydrolase (XTH) on the extension of isolated cell walls.
Methods: The epidermis of growing onion (Allium cepa) bulb scales is a one-cell-thick model tissue that is structurally and mechanically highly anisotropic. In constant load experiments, the effect of purified recombinant XTH proteins of Selaginella kraussiana on the extension of isolated onion epidermis was recorded.
Key Results: Fluorescent xyloglucan endotransglucosylase (XET) assays demonstrate that exogeneous XTH can act on isolated onion epidermis cell walls. Furthermore, cell wall extension was significantly increased upon addition of XTH to the isolated epidermis, but only transverse to the net orientation of cellulose microfibrils.
Conclusions: The results provide evidence that XTHs can act as cell wall-loosening enzymes.
Key words: XTH, XET activity, primary cell wall, xyloglucan, cellulose microfibrils, cellulose orientation, cell expansion, cell wall loosening, extensiometry, onion (Allium cepa), Selaginella kraussiana
These authors contributed equally to this work.
Present address: Laboratory of Functional Activity of Membranes, Biological Research Institute of Saint-Petersburg State University, Oranienbaumskoye sh. 2, Stary Peterhof, 198504 Saint-Petersburg, Russia.
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