Regulation of glutamine synthetase messenger ribonucleic acid in connidia of Neurospora crassa.

A large quantity of prepackaged mRNA is present in conidia ofNeurospora crassa as evidenced by its capacity to direct the synthesis of proteins in two heterologous cell-free systems. With this mRNA noin vitro synthesis of glutamine synthetase could be detected by specific immunoprecipitation. Upon incubation of the conidia under nongrowing conditions, the specific mRNA for glutamine synthetase was evidenced in the polyadenylated RNA and to a lesser degree in the nonpolyadenylated RNA. The amount of specific mRNA correlated well with the specific activity of glutamine synthetase in the conidia, which was dependent on the nitrogen source in the incubation medium. Based on these results we propose that conidia ofN. crassa regulate its glutamine synthetase activity at the transcriptional level.