Gene control of developmental competence in Aspergillus nidulans

Conidia of Aspergillus nidulans placed in liquid nutrient medium germinate to produce hyphae that grow for a day or more as undifferentiated colonies. After 20 hr of growth, but not before, such colonies become responsive to induction and develop conidia-bearing structures (conidiophores) after being placed onto the surface of media-saturated membrane filters. Thus the time at which these colonies become developmentally competent is 20 hr. A mutant has been isolated which is indistinguishable from the wild-type strain except that it becomes competent to be induced 2 hr before the wild-type strain. At least one gene controlling competence has been characterized as a chromosomal allele. We have therefore been able to measure the time at which a growing colony becomes developmentally competent, and have shown that competence is under genetic control.