Jiangsu Key Laboratory for Microbes and Microbial Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Science, Nanjing Normal University, Nanjing, People's Republic of China.
Jiangsu Key Laboratory for Microbes and Microbial Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Science, Nanjing Normal University, Nanjing, People's Republic of China
Appl Environ Microbiol. 2019 Oct 16;85(21). doi: 10.1128/AEM.01345-19. Print 2019 Nov 1.
This study reports that a high concentration of the endo-β-1,3-glucanase ENG (200 μg ml) induced heat-inactivated stipe wall extension of , whereas a high concentration of the extracellular β-glucosidase BGL2 (1,000 μg ml) did not; however, in combination, low concentrations of ENG (25 μg ml) and BGL2 (260 μg ml) induced heat-inactivated stipe cell wall extension. In contrast to the previously reported chitinase-reconstituted stipe wall extension, β-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 β-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 β-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 β-1,6 branched β-1,3-glucans but also to other polysaccharides. Remarkably, a low concentration of either the β-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. We previously reported that the chitinase could induce stipe wall extension and was involved in stipe elongation growth of the mushroom In this study, we explored that β-1,3-glucanase also induced stipe cell wall extension. Interestingly, the extension profile and extended ultra-architecture of β-1,3-glucanase-reconstituted stipe wall were different from those of chitinase-reconstituted stipe wall. However, β-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 β-1,3-glucanases is necessary for the cell wall remodeling and the addition of new β-glucans during stipe elongation growth.
这项研究报告称，高浓度的内-β-1,3-葡聚糖酶 ENG（200μg/ml）诱导热失活的菌柄细胞壁延伸，而高浓度的胞外β-葡糖苷酶 BGL2（1000μg/ml）则没有；然而，低浓度的 ENG（25μg/ml）和 BGL2（260μg/ml）组合可以诱导热失活的菌柄细胞壁延伸。与先前报道的几丁质酶重建的菌柄细胞壁延伸不同，β-1,3-葡聚糖酶重建的热失活菌柄细胞壁延伸最初表现出快速的延伸速率，大约 60 分钟后迅速降至零；高浓度的β-1,3-葡聚糖酶诱导的菌柄细胞壁延伸在测量过程中不会导致菌柄断裂，并且葡聚糖酶重建的延伸细胞壁的内表面仍然保持无定形基质，似乎没有受损。β-1,3-葡聚糖酶重建的细胞壁延伸的这些独特特征可能是因为几丁质链不仅与侧链的非还原末端和β-1,6 分支β-1,3-葡聚糖的骨架交联，而且还与其他多糖交联。值得注意的是，低浓度的β-1,3-葡聚糖酶 ENG 或几丁质酶 ChiE1 都不会诱导热失活的菌柄细胞壁延伸，但是这两种酶的组合，每种酶的浓度都很低，表现出稳定且连续的细胞壁延伸轮廓的菌柄细胞壁延伸活性。因此，我们得出结论，菌柄细胞壁的延伸是葡聚糖酶和几丁质酶协同作用的结果。我们之前报道过，几丁质酶可以诱导菌柄壁延伸，并参与蘑菇菌柄的伸长生长。在这项研究中，我们探索了β-1,3-葡聚糖酶也可以诱导菌柄细胞壁延伸。有趣的是，β-1,3-葡聚糖酶重建的菌柄细胞壁的延伸轮廓和延伸的超结构与几丁质酶重建的菌柄细胞壁不同。然而，β-1,3-葡聚糖酶与几丁质酶合作诱导菌柄细胞壁延伸。葡聚糖酶和几丁质酶之间的这种协同作用的意义在于，它可以使低浓度的活性酶诱导细胞壁延伸，并且β-1,3-葡聚糖酶的参与对于菌柄伸长生长过程中的细胞壁重塑和新的β-葡聚糖的添加是必要的。
