Figure 10.

Maintaining high levels of NIMX^cdc2 kinase activity in the nimX^cdc2AF mutant fails to prevent DNA over-replication. The nimX^cdc2AF + alcA::nimE^{cyclin BΔD} strain, which contains a nondegradable (D box minus) nimE^{cyclin B} under control of the alcA promoter, and a wild-type strain were first germinated in minimal medium containing acetate (repressing) in the presence of 6 mM HU. Cells were allowed to undergo the first premature mitosis, which occurs after 9 h in minimal medium. Expression of nimE^{cyclin B ΔD} was then allowed by transferring cells to glycerol-containing medium. DAPI staining of representative cells of (A) the wild-type and (B) nimX^cdc2AF + alcA::nimE^{cyclin BΔD} strains after 7 h growth in glycerol-containing medium. Please note that when grown in minimal medium A. nidulans cells are much thinner than those shown in nutrient-rich medium (Figure 5). (C) p34^cdc2 H1 kinase activity was isolated from the nimX^cdc2AF + alcA::nimE^{cyclin BΔD} strain at the indicated times after transfer to glycerol-containing medium. Bar, 5 μm.