Glucanase-Induced Stipe Wall Extension Shows Distinct Differences from Chitinase-Induced Stipe Wall Extension of Coprinopsis cinerea.

ABSTRACT

This study reports that a high concentration of the endo-ß-1,3-glucanase ENG (200 µg ml-1) induced heat-inactivated stipe wall extension of Coprinopsis cinerea, whereas a high concentration of the extracellular ß-glucosidase BGL2 (1,000 µg ml-1) did not; however, in combination, low concentrations of ENG (25 µg ml-1) and BGL2 (260 µg ml-1) induced heat-inactivated stipe cell wall extension. In contrast to the previously reported chitinase-reconstituted stipe wall extension, ß-1,3-glucanase-reconstituted heat-inactivated stipe cell wall extension initially exhibited a fast extension rate that quickly decreased to zero after approximately 60 min; the stipe cell wall extension induced by a high concentration of ß-1,3-glucanase did not result in stipe breakage during measurement, and the inner surfaces of glucanase-reconstituted extended cell walls still remained as amorphous matrices that did not appear to have been damaged. These distinctive features of the ß-1,3-glucanase-reconstituted wall extension may be because chitin chains are cross-linked not only to the nonreducing termini of the side chains and the backbones of ß-1,6 branched ß-1,3-glucans but also to other polysaccharides. Remarkably, a low concentration of either the ß-1,3-glucanase ENG or of chitinase ChiE1 did not induce heat-inactivated stipe wall extension, but a combination of these two enzymes, each at a low concentration, showed stipe cell wall extension activity that exhibited a steady and continuous wall extension profile. Therefore, we concluded that the stipe cell wall extension is the result of the synergistic actions of glucanases and chitinases.IMPORTANCE We previously reported that the chitinase could induce stipe wall extension and was involved in stipe elongation growth of the mushroom Coprinopsis cinerea In this study, we explored that ß-1,3-glucanase also induced stipe cell wall extension. Interestingly, the extension profile and extended ultra-architecture of ß-1,3-glucanase-reconstituted stipe wall were different from those of chitinase-reconstituted stipe wall. However, ß-1,3-glucanase cooperated with chitinase to induce stipe cell wall extension. The significance of this synergy between glucanases and chitinases is that it enables a low concentration of active enzymes to induce wall extension, and the involvement of ß-1,3-glucanases is necessary for the cell wall remodeling and the addition of new ß-glucans during stipe elongation growth.