Control of gene action in Aspergillus nidulans

Abstract

Aspergillus nidulans has been studied to determine the extent to which the mechanisms regulating gene activity in eukaryotes resemble those in bacteria and viruses. The following are our principal findings: (1) The nuclear membrane may play a regulatory role. The characteristics of certain mutations is consistent with there being nuclear permeases in Aspergillus , and with some control systems being localized within the nucleus. (2) The control of nitrate reduction involves a regulator substance with a positive mode of action, i. e. it is required to activate gene expression. The control system in this case cannot be localized within the nucleus. Nitrate reductase itself functions as the co-repressor of enzyme synthesis. (3) The structural genes involved in nitrate reduction are not grouped in an operon, although operons may exist for other systems in Aspergillus . (4) Ammonium represses the synthesis of enzymes in many pathways. mea R mutants show pathway-wide derepression. The mea gene may produce a regulator substance which interacts with each of these systems.