Figure 2.—

Growth tests of the uaY12 mutant and of some of its revertants. (A) Comparison of the growth on adenine, hypoxanthine, and uric acid of uaY12 and some other uaY⁻ mutants. uaY2 corresponds to a null uaY allele and uaY109 to a leaky allele (see supplemental material for full genotypes, and materials and methods for the sequence of the mutations). These strains were plated on supplemented minimal media containing 5 mm of ammonium tartrate (NH₄⁺) or 0.1 mg/ml of adenine (Ad), hypoxanthine (HX), or uric acid (UA) as sole nitrogen sources. Plates were incubated for 2 days at 37°. At the top, the uaY alleles carried by each strain are indicated. A. nidulans coniospores are able to germinate on media without any utilizable nitrogen source, leading to low hyphal density and sparse sporulation, as illustrated by the residual growth of the null uaY2 mutant. (B) Growth test of uaY12 revertants. Conditions as in A, except that the plates at 25° were incubated for 4 days and the test on adenine was not included. “ +” indicates the wild-type strain (NA9910) and “12” the uaY12 strain used in the reversion experiment (NA9926). All the strains are in the same genetic background (yA2 riboC3 pyroA4) except the 12r128 strain (yA2 pantoB100 pyroA4).