TEMPERATURE-SENSITIVE PLEIOTROPIC REVERTANTS FROM A MUTANT IN THE AROM GENE CLUSTER OF NEUROSPORA CRASSA

Genetical and biochemical studies have been performed with revertants induced in a polyaromatic mutant (No. 58) in the arom gene cluster of Neurospora crassa. In addition to complete and partial revertants able to grow on minimal at both 25° and 35°, temperature-sensitive revertants capable of growth on minimal at 25° but not at 35° have been recovered. One of these revertants has been shown to lack biosynthetic dehydroquinase activity at both temperatures (utilizing the inducible catabolic isozyme for growth at 25°), to have dehydroshikimate reductase activity only at 25°, and to form an arom aggregate having a molecular weight approximately one-half that of wild type. These results are interpreted as indicating that pleiotropic mutants in the arom gene cluster can result from missense mutations, as well as from nonsense mutations as indicated in previous studies.