title: Stipe wall extension of Flammulina velutipes could be induced by an expansin-like protein from Helix aspersa.
abstract: Expansin proteins extend plant cell walls by a hydrolysis-free process that disrupts hydrogen bonding between cell wall polysaccharides. However, it is unknown if this mechanism is operative in mushrooms. Herein we report that the native wall extension activity was located exclusively in the 10 mm apical region of 30 mm Flammulina velutipes stipes. The elongation growth was restricted also to the 9 mm apical region of the stipes where the elongation growth of the 1st millimetre was 40-fold greater than that of the 5th millimetre. Therefore, the wall extension activity represents elongation growth of the stipe. The low concentration of expansin-like protein in F. velutipes stipes prevented its isolation. However, we purified an expansin-like protein from snail stomach juice which reconstituted heat-inactivated stipe wall extension without hydrolytic activity. So the previous hypotheses that stipe wall extension was resulted from hydrolysis of wall polymers by enzymes or disruption of hydrogen bonding of wall polymers exclusively by turgor pressure are challenged. We suggest that stipe wall extension may be mediated by endogenous expansin-like proteins that facilitate cell wall polymer slippage by disrupting noncovalent bonding between glucan chains or chitin chains.
authors.affiliation: 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 210023, PR China.
authors.forename: Hejian
authors.initials: H
authors.lastname: Fang
authors.affiliation: 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 210023, PR China.
authors.forename: Wenming
authors.initials: W
authors.lastname: Zhang
authors.affiliation: 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 210023, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Niu
authors.affiliation: 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 210023, PR China.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Liu
authors.affiliation: 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 210023, PR China.
authors.forename: Changmei
authors.initials: C
authors.lastname: Lu
authors.affiliation: 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 210023, PR China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wei
authors.affiliation: 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 210023, PR China. Electronic address: yuansheng@njnu.edu.cn.
authors.forename: Sheng
authors.initials: S
authors.lastname: Yuan
mesh_terms: D000818:Animals; D002473:Cell Wall / Q000187:drug effects* / Q000378:metabolism; D055393:Flammulina / Q000187:drug effects* / Q000378:metabolism; D005750:Gastric Juice / Q000737:chemistry; D011506:Proteins / Q000302:isolation & purification* / Q000378:metabolism*; D012908:Snails / Q000737:chemistry*
chemical_list: D011506:Proteins
keywords: Cell walls; Fruit body; Snail; Stipe elongation; Wall extension activity