Xyloglucan endotransglucosylase activity loosens a plant cell wall.
OBJECTIVE
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.


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.
Van Sandt
Vicky S T
VS
University of Antwerpen, Biology Department, Groenenborgerlaan 171, 2020 Antwerpen, Belgium.
Suslov
Dmitry
D
Verbelen
Jean-Pierre
JP
Vissenberg
Kris
K
D002473:Cell Wall / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D005936:Glucans / Q000378:metabolism; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D019697:Onions / Q000201:enzymology / Q000378:metabolism; D019441:Plant Epidermis / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D032503:Selaginellaceae / Q000201:enzymology / Q000378:metabolism; D014990:Xylans / Q000378:metabolism
D005936:Glucans; D011994:Recombinant Proteins; D014990:Xylans; C029353:xyloglucan; D002482:Cellulose; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase