Abstract
ABSTRACT
Under the influence of the pheromone, “circein,” produced by an oogonial mother cell of Oedogonium donnellii Wolle, the androspore of the same species progresses through several behavioral changes and a series of developmental stages which result in the formation of a sperm‐producing dwarf male thallus. When subjected instead to an environment with an increased nitrate or ammonium ion concentration [0.02 M KNO3 or 0.01 M (NH)2SO4], an androspore undergoes a series of developmental changes which result in the formation of a vegetative male thallus indistinguishable from the one which originally released it. If exposed to neither circein nor increased nitrate/ammonium ion concentration, the androspore enters a cycle of swimming androspore: cyst: swimming androspore. Thus, three separate paths are open to the androspore depending on its environment: (1) development into a dwarf male thallus under the influence of female‐produced pheromone, circein, (2) development into a vegetative thallus under the influence of increased nitrate/ammonium ion concentration, and (3) periodic regeneration through an encystment cycle in an unaltered environment. Treatments with transcriptional and translational inhibitors indicate that androspore development into either a dwarf male or a vegetative thallus requires several different phases of de novo synthesis of RXA and protein stimulated by circein or by nitrate ion.