title: Fungal hemicellulose-degrading enzymes cause physical property changes concomitant with solubilization of cell wall polysaccharides.
abstract: Physical properties of wheat coleoptile segments decreased after treatment with hemicellulose-degrading enzymes, indicating that hemicellulosic polysaccharides function to control the strength of primary cell walls. Changes in the physical properties of plant cell walls, a viscoelastic structure, are thought to be one of the growth-limiting factors for plants and one of the infection-affecting factors for fungi. To study the significance of hemicellulosic polysaccharides that form cross-bridges between cellulose microfibrils in controlling cell wall strength in monocot plants, the effects of hemicellulose degradation by recombinant Magnaporthe oryzae xylanase and 1,3-1,4-β-glucanase, and recombinant Aspergillus oryzae xyloglucanase on the physical properties and polysaccharide solubilization were investigated using wheat (Triticum aestivum L.) coleoptiles. Treatments with xylanase or 1,3-1,4-β-glucanase significantly decreased the viscosity and elasticity of wheat coleoptile segments. In addition, xyloglucanase treatment slightly decreased the viscoelasticity. Furthermore, 1,3-1,4-β-glucan polymer was solubilized during hydrolysis with xylanase and xyloglucanase, even though neither enzyme had hydrolytic activity towards 1,3-1,4-β-glucan. These results suggest that xylan and xyloglucan interact with 1,3-1,4-β-glucan and that the composites and hemicellulosic polysaccharides form inter-molecular bridges. Degradation of these bridges causes decreases in the physical properties, resulting in increased extensibility of the cell walls. These findings provide a testable model in which wheat coleoptile cell walls are loosened by the degradation of hemicellulosic polysaccharides and hemicellulose-degrading enzymes play a significant role in loosening the walls during fungal infection.
authors.affiliation: Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate, 024-0003, Japan.
authors.forename: Machiko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Yamamoto
authors.forename: Naoki
authors.initials: N
authors.lastname: Sakurai
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakano
authors.forename: Takumi
authors.initials: T
authors.lastname: Takeda
mesh_terms: D001236:Aspergillus oryzae / Q000201:enzymology / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism*; D020082:Magnaporthe / Q000201:enzymology / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*; D014990:Xylans / Q000378:metabolism
chemical_list: D005936:Glucans; D011134:Polysaccharides; D014990:Xylans; C029353:xyloglucan; C007916:hemicellulose; D006026:Glycoside Hydrolases; C072818:xyloglucan endo(1-4)-beta-D-glucanase