Low molecular weight sulphydryl compounds and the expression of a cell division mutant of Chlamydomonas reinhardi

Abstract

Cultures of the cytokinesis-deficient mutant of Chlamydomonas reinhardi, cyt 1 normally contain a mixture of uninucleate, binucleate and multinucleate cells. Inclusion of ethanol, diamide or mercaptoethanol in the culture medium increases the proportions of binucleate and multinucleate cells. A similar effect has previously been found with both cobalt and benzimidazole. Ethanol, cobalt and benzimidazole all raise internal cysteine or cystine levels very markedly in both mutant and wild-type cells. Changes in free cysteine or cystine levels and proportions of multinucleate cells in the mutant are induced over similar concentrations of ethanol and over similar time periods in a fixed concentration of ethanol. Diamide, thought to be a specific glutathione oxidising agent, and mercaptoethanol do not raise internal cysteine/ cystine levels. Agents which induce changes in levels of sulphydryl compounds or their oxidation-reduction status therefore seem to alter the expression of the mutant. Since similar changes in sulphydryl compounds only produce much lesser effects in cell division in wild type cells, it is proposed that cells of the mutant cyt 1 are in some way hypersensitive to such changes.