Structure, synthesis and orientation of microfibrils. VI. The role of ions in microfibril deposition in Oocystis solitaria.

The action of a series of chelators, cryptates and ionophores on microfibril deposition and the presence of cortical microtubules in Oocystis solitaria has been investigated. Having a potent inhibitory effect on cellulose synthesis were the calcium ionophores A 23187 and X-537A, the flourescent calcium chelator chlorotetracycline and the cryptates 211 and 221. Only at unphysiological concentrations, e.g. 100 mM or more, were the chelators EDTA and EGTA effective in completely inhibitory cellulose synthesis. A reduction in the rate of cellulose synthesis was observed with the sodium-selectiv ionophore dianemycin. This partial inhibition was independent of the ionophore concentration. Without effect on microfibril deposition were the potassium-selective ionophore valinomycin and cryptate 222. In all cases, whether cellulose synthesis is blocked or not, none of the above agents prevented the reassembly of cortical microtubules when applied during the recovery from colchicine treatment. Destruction of cortical microtubules through the calcium ionophore may be achieved, but only when additional (2 mM) calcium is added to the culture medium.