Fig. 4. nimU is an essential gene. (A) Wild type, nimU24 and nimU spores were grown for 14 hours at permissive and restrictive temperatures for nimU24, then fixed and stained with DAPI. The wild-type strain grew normally at both temperatures, producing multinucleate hyphae. nimU24 spores produced multinucleate hyphae at the permissive temperature, but only grossly enlarged nuclei at the restrictive temperature. The nimU spores produced grossly enlarged nuclei at both temperatures.