Ammonium ions and glutamine inhibit sporulation of Coprinus cinereus basidia assayed in vitro

Basidia of Coprinus cinereus (Schaeff.:Fr) S. F. Gray are committed to their developmental pathway, continuing through meiosis and sporulation even when excised from their parental fruit body. A technique is described which permits this in vitro differentiation to be used as a rapid, small-scale bioassay for chemicals which interfere with these morphogenetic processes. Of a range of compounds tested, only ammonium and glutamine, and some structural analogues, were able to inhibit basidium differentiation. Growth was not inhibited; instead the differentiation inhibitors caused vegetative hyphal tips to grow out from regions of the basidial apparatus expected to be in active growth during sporulation. Depending on the stage reached at the time of exposure to the inhibitors, vegetative hyphal tips emerged from the four apical sites for sterigmata, from the tips of sterigmata, from partially formed or abnormal spores, and from the basal regions of the basidium from which paraphyses would be expected to arise. The experiments show that ammonium ions and glutamine halt meiocyte differentiation. Reports of similar effects in other organisms, animals and plants as well as fungi, may imply that sporulation events are generally sensitive to ammonium inhibition.