Temporal and spatial changes of cellulose synthesis inClosterium acerosum (Schrank) Ehrenberg during cell growth

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Abstract
The amount and distribution of wall microfibril synthesis were investigated in the cell-division cycle ofClosterium acerosum. Electron-microscopic examination and a methylation analysis of alkali-extracted wall fragments showed that alkali-extracted wall was mainly composed of microfibrils and that the microfibrils ofC. acerosum were 4-linked glucans, i.e., cellulose. Cellulose synthesis was measured as incorporation of14C, fed to cells as NaHCO3, into extracted wall fragments. Extensive cellulose synthesis was coincident with septum formation, continued for more than 6 h and then ceased. It was found by microautoradiography that cellulose synthesis after cell division was essentially restricted to the expanding new semicells. Such a restricted distribution of cellulose synthesis was maintained for more than 6 h after septum formation, i.e., for more than 2 h after the cessation of expansion; afterwards, cellulose synthesis in some, but not all, cells became extended to the old semicells, and then ceased. Considerable cellulose synthesis also took place in the band-like expanding part of non-divided cells, indicating that cell division was not necessarily required for the induction of cellulose synthesis and the latter was coupled with cell expansion. Extension of cellulose synthesis to old semicells was brought about in divided cells by treatment with 3 mM colchicine, 28 μM vinblastine, 50 μM isopropyl-N-phenylcarbamate or 1 μM isopropyl-N(3-chlorophenyl)carbamate, indicating that microtubules are involved in the limitation of cellulose synthesis to the new semicells.