A fungal endoglucanase with plant cell wall extension activity.
We have identified a wall hydrolytic enzyme from Trichoderma reesei with potent ability to induce extension of heat-inactivated type I cell walls. It is a small (23-kD) endo-1,4-beta-glucanase (Cel12A) belonging to glycoside hydrolase family 12. Extension of heat-inactivated walls from cucumber (Cucumis sativus cv Burpee Pickler) hypocotyls was induced by Cel12A after a distinct lag time and was accompanied by a large increase in wall plasticity and elasticity. Cel12A also increased the rate of stress relaxation of isolated walls at very short times (<200 ms; equivalent to reducing t(0), a parameter that estimates the minimum relaxation time). Similar changes in wall plasticity and elasticity were observed in wheat (Triticum aestivum cv Pennmore Winter) coleoptile (type II) walls, which showed only a negligible extension in response to Cel12A treatment. Thus, Cel12A modifies both type I and II walls, but substantial extension is found only in type I walls. Cel12A has strong endo-glucanase activity against xyloglucan and (1-->3,1-->4)-beta-glucan, but did not exhibit endo-xylanase, endo-mannase, or endo-galactanase activities. In terms of kinetics of action and effects on wall rheology, wall loosening by Cel12A differs qualitatively from the action by expansins, which induce wall extension by a non-hydrolytic polymer creep mechanism. The action by Cel12A mimics some of the changes in wall rheology found after auxin-induced growth. The strategy used here to identify Cel12A could be used to identify analogous plant enzymes that cause auxin-induced changes in cell wall rheology.
Yuan
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S
Department of Biology, 208 Mueller Lab, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Wu
Y
Y
Cosgrove
D J
DJ
D001696:Biomechanical Phenomena; D002455:Cell Division / Q000187:drug effects; D002473:Cell Wall / Q000382:microbiology / Q000502:physiology; D002480:Cellulase / Q000378:metabolism*; D018553:Cucumis sativus / Q000382:microbiology*; D005656:Fungal Proteins / Q000378:metabolism*; D006358:Hot Temperature; D018546:Hypocotyl / Q000382:microbiology / Q000502:physiology; D007700:Kinetics; D010935:Plant Diseases; D010940:Plant Proteins / Q000032:analysis; D014242:Trichoderma / Q000201:enzymology / Q000472:pathogenicity*; D014908:Triticum / Q000382:microbiology / Q000502:physiology
D005656:Fungal Proteins; D010940:Plant Proteins; C095825:expansin protein, plant; D002480:Cellulase