CA2+ CALMODULIN-DEPENDENT KINASE IS ESSENTIAL FOR BOTH GROWTH AND NUCLEAR DIVISION IN ASPERGILLUS-NIDULANS/

The calmodulin gene has been shown to be essential for cell cycle prog ression in a number of eukaryotic organisms. In vertebrates and Asperg illus nidulans the calmodulin dependence also requires calcium. We dem onstrate that the unique gene encoding a multifunctional calcium/calmo dulin-dependent protein kinase (CaMK) is also essential in A. nidulans . This enzyme is required both for the nuclear division cycle and for hyphal growth, because spores containing the disrupted gene arrest wit h a single nucleus and fail to extend a germ tube. A strain conditiona l for the expression of CaMK was created. When grown under conditions that resulted in a 90% decrease in the enzyme, both nuclear division a nd growth were markedly slowed. The CaMK seems to be important for pro gression from G(2) to mitosis.