TEMPERATURE CONDITIONAL CAMP-REQUIRING MUTANT STRAINS OF CHLAMYDOMONAS REINHARDTII ARREST IN G(1) AND ARE RESCUED BY ADDED CAMP

摘要

Three independent isolates of Chlamydomonas, selected for caffeine resistance, were found to arrest in G(1) phase, as determined by quantitative fluorescence measurements of DNA, when grown at a non-permissive temperature. This cell cycle arrest correlated with lowered levels of cAMP and of adenylate cyclase activity. The arrested cells could be rescued by added cAMP but not AMP, hence the defect was not one of general purine metabolism. Back-crosses to wild type revealed that the phenotypes observed result from a combination of three separable mutations. It is clear that the mutations define functions that are more stringently required for cell division than for growth since the mutant strains are able to grow up to fifteen times normal size while blocked at the non-permissive temperature. The possible interaction of cAMP dependent events with division is discussed. [References: 43]