Cover photograph (Copyright © 2001, American Society for Microbiology. All rights reserved.): The filamentous fungus Aspergillus nidulans is a model organism to study developmental processes. It produces haploid conidiospores on top of a differentiated structure called a conidiophore. We isolated a mutant which is strongly reduced in conidiospore formation, and therefore colonies are brown and not green like the wild type. Molecular analysis revealed that two genes are affected in this strain, the central regulatory gene brlA and pclA, which encodes a cyclin homologue and interacts with a cyclin-dependent kinase. The scanning electron micrograph of the mutant conidiophore was taken in collaboration with A. Hassel and G. Kost (University of Marburg). (See related article on page 4075.)