Cell biology of spatial regulation of formation of the cell wall

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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.