Isolation of a Gene That Down-Regulates Nitrate Assimilation and Influences Another Regulatory Gene in the Same System

Glutamine is the preferred source of nitrogen of Neurospora crassa. In its presence and that of the gene product of MSS (nmr-1), the fungus represses the assimilation of less preferred forms of nitrogen, such as nitrate. In the absence of glutamine and the presence of the product of gene nit-2, less preferred forms of nitrogen are assimilated as long as a specific pathway for their assimilation is induced. We report here the isolation, from a …