DEVELOPMENTAL REPRESSION OF GROWTH AND GENE-EXPRESSION IN ASPERGILLUS

Asexual reproductive development can be initiated in Aspergillus nidulans in the presence of excess nutrients through artificial induction of the developmental regulatory genes brlA or abaA by fusing the genes to the promoter from the alcohol dehydrogenase I gene (alcA) and culturing cells in the presence of an inducing alcohol. Artificially induced development completely inhibits growth and represses expression of the endogenous alcA gene and the coordinately controlled aldehyde dehydrogenase gene (aldA). Repression of alcA and aldA expression probably occurs at both the transcriptional and posttranslational levels. We propose that developmental induction results in a generalized metabolic shutdown, leading to an inability of cells to acquire nutrients from the growth medium. Self-imposed nutrient limitation could reinforce the primary developmental stimulus and ensure progression through the asexual reproductive pathway.