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.
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.
Fungal Biol. 2014 Jan;118(1):1-11. doi: 10.1016/j.funbio.2013.10.003. Epub 2013 Oct 31.
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.
扩展蛋白通过一种不依赖于水解的过程扩展植物细胞壁，该过程破坏细胞壁多糖之间的氢键。然而，目前尚不清楚这种机制是否在蘑菇中起作用。本文报道了天然的细胞壁延伸活性仅存在于 30mm 金针菇梗的 10mm 顶端区域。伸长生长也仅限于梗的 9mm 顶端区域，其中 1mm 处的伸长生长是第 5mm 处的 40 倍。因此，细胞壁延伸活性代表了梗的伸长生长。金针菇梗中低浓度的扩展素样蛋白阻碍了其分离。然而，我们从蜗牛胃液中纯化了一种扩展素样蛋白，它可以重新构成热失活的梗细胞壁延伸，而没有水解活性。因此，以前关于梗细胞壁延伸是由酶水解细胞壁聚合物或仅由膨压破坏细胞壁聚合物氢键引起的假设受到了挑战。我们认为，梗细胞壁的延伸可能是由内源性扩展素样蛋白介导的，这些蛋白通过破坏葡聚糖链或几丁质链之间的非共价键，促进细胞壁聚合物的滑动。
