[Use of a pyrimidine-dependent mutant for effective labeling of the DNA OF Aspergillus nidulans].

Incorporation of the radioactive label from pyrimidines into RNA and DNA of an Aspergillus nidulans pyrimidine-dependent mutant was studied. The label from [14C2]uridine was incorporated at the highest rate into both fractions of nucleic acids from A. nidulans of the wild type and pyr-mutant. The content of the label in the DNA of the pyr-mutant was several times higher than that in the wild type DNA. Therefore, pyr-mutants can be used in order to study molecular-genetic processes in the cells of A. nidulans. The label from [3H5]deoxyuridine, [14C2]thymine, [14C2]thymidine, [14C2]cytosine and I114C2]uracil was incorporated into the pyr-mutant RNA and DNA at a much lower rate than into the wild type RNA and DNA. Apparently, these pyrimidines cannot maintain the growth of the pyr-mutant. Incorporation of the label from [14C2]uracil into the pyr-mutant DNA increased if growth of the mycelium was stimulated by low concentrations of unlabeled uridine.