Conidiophore and spore development in Aspergillus nidulans.

Abstract

SUMMARY: Conidiophore development was studied in wild-type and structurally defective mutants of Aspergillus nidulans. Cytoplasmic vesicles were found concentrated at growing apices. Plasmalemmasomes occurred frequently in the subapical and basal cytoplasm of growing sterigmata and near their developing septa; after septum formation they were flattened against the septa and the wall of the older cell and were associated with lomasomes. At this stage the wall developed a superficial lamina; the basipetally budding spore chain was invested from its initiation by a continuation of this lamina. The lamina was also associated with a dense network in the medium around the basal mycelium. The inner, secondary wall of the conidiophore became more electron-lucent with age; the continuity between this wall and the single wall of the sterigmata suggested this structure to be the site of action of the bristle locus. Pigmentation of wild-type and mutant conidiophores was associated with an electron-dense modification of the outer, primary wall. Stratification of the spore wall was indicated only by the similar development of a layer of electron-dense material. Cytoplasmic microfilaments were observed in all parts of the colony.