Co-ordinate control of ammonium-scavenging enzymes in the fruit body cap ofCoprinus cinereusavoids inhibition of sporulation by ammonium

Abstract

Observation of stained nuclei coupled with determination of activity of NADP-linked glutamate dehydrogenase (NADP-GDH) and glutamine synthetase (GS) in the same tissue, showed that increase in activity of both enzymes was initiated as karyogamy became evident in normally-developing basidia of fruit bodies of the basidiomycete Coprinus cinereus. Derepression of the two enzymes was highly positively correlated (correlation coefficient 0.91), implying co-ordinated regulation. Application and injection of solutions of ammonium salts to Coprinus fruit body caps arrested further development. Other salts had no such effect, indicating a specific sensitivity to ammonium. Similar enzymic events occur during sporulation of Saccharomyces cerevisiae, which is also sensitive to inhibition by ammonium salts. It is concluded that meiosis generally includes ammonium-sensitive processes and that co-ordinated derepression of the ammonium scavenging NADP-GDH and GS is a device to ensure removal of ammonium ions from the meiotic cell.