Cell biology of spatial regulation of formation of the cell wall

1.红豆杉细胞壁局部沉积过程中皮层微管的参与表现为有边坑的形成。建立了一种观察墙体三维结构的方法。用这种方法在豌豆上胚轴中发现纤维素微原纤维在进入核区后立即中断。这表明二次增稠的质膜结构域和坑区分别激活和灭活纤维素合酶。3.半纤维素仅在二次增稠中分布。这表明纤维素和半纤维素的沉积至少在一定程度上是由相同的机制控制的。4.氨丙磷对微管的破坏扰乱了纤维素和半纤维素的沉积模式，其方式与二次增厚的沉积模式相同。这意味着微管定义了增厚和凹坑之间的边界。5.基于以上结果，我提出以下假设：携带纤维素合酶和半纤维素的高尔基囊泡只与二次增稠的PM融合。纤维素合酶携带到PM在增稠的PM中合成纤维素微原纤维，但当进入坑的PM时失去活性。皮层微管定义增厚的PM结构域和小窝之间的边界。6.为了证明这一假设，我们尝试用Closterium细胞分离和鉴定与壁合成相关的PM蛋白。合成多纤维素细胞和合成少纤维素细胞的PM蛋白在二维PAGE斑点图案上存在一些差异。

1.Involvement of cortical microtubules in localized deposition of the cell wall was demonstrated in formation of bordered pit in Taxus. 2.A method to observe three dimensional structure of the wall was established. It was found in pea epicotyls by this method that cellulose microfibrils are interrupted immediately after entering into the pit areas. This indicates that the plasma membrane(PM) domains of secondary thickenings and pit areas activate and inactivate cellulose synthase, respectively. 3.Hemicellulose was distributed only in secondary thickenings. This indicates that depositions of cellulose and hemicellulose are controlled at least in part by the same mechanism. 4.Disruption of microtubules by amiprophos-methyl disordered deposition patterns of cellulose and hemicellulose in the same way as did the deposition pattern of the secondary thickening. This means that microtubules define the boundary between the thickening and the pit. 5.Based on the above results, I proposed the following hypothesis : Golgi vesicles carrying cellulose synthase and hemicelluloses fuse only with the PM of the secondary thickenings. Cellulose synthases carried to the PM synthesize cellulose microfibrils in the PM of the thickening but lose their activity when entering into the PM of the pit. Cortical microtubules define the boundary between the PM domains in the thickening and the pit. 6.Toward proving this hypothesis, separation and identification of PM proteins related to wall synthesis was tried using Closterium cells. Some differences in spot patterns of two dimensional PAGE were detected between PM proteins of cells synthesizing much and little cellulose.