CERATOPTERIS - A MODEL SYSTEM FOR STUDYING SEX-DETERMINING MECHANISMS IN PLANTS

The homosporous fern Ceratopteris richardii is a model system for studying the genetic and epigenetic factors that are involved in sex-determining processes in plants. The sex of the Ceratopteris gametophyte is determined by antheridiogen, a gibberellin-like pheromone that is secreted by the hermaphroditic gametophyte and promotes male development of sexually immature gametophytes. Abscisic acid blocks the antheridiogen response in Ceratopteris. Several mutations that affect sex expression have been isolated and characterized; these mutations define at least some of the major regulatory genes that are involved in determining the sex of the Ceratopteris gametophyte. By studying the epistatic interactions among these mutants, it is possible to determine how these genes interact with one another to form a regulatory genetic hierarchy that controls sex determination and expression in Ceratopteris. While a genetic approach is useful in identifying genes that are involved in sex determination, other molecular approaches have been successfully employed in isolating sex-specific genes in Ceratopteris as well as genes involved in other aspects of its reproductive development.