9405780 Banks The primary objective of this proposal is to use a genetic approach to understand how antheridiogen and abscisic acid govern the sex of the gametophyte of Ceratopteris. At least some key regulatory genes involved in sex determination have been identified by generating and characterizing mutations that alter the normal sexual phenotype. A hypothetical model of how these genes interact in a regulatory hierarchy has been proposed. One objective of the proposed research is to continue with the genetic, morphological genes and physiological analysis of these mutants in order to understand the wild type functions of these genes and to further test and modify the proposed model of gene interaction. %%% Gametophytes of the fern Ceratopteris richardii are either hermaphroditic or male. The primary sex-determining signal in this and many other ferns is antheridiogen a gibberellin-like pheromone that is secreted by the hermaphroditic gametophyte and promotes male development of other sexually undetermined juvenile gametophytes. The plant hormone abscisic acid blocks the antheridiogen response. How sex is determined in plants is an important developmental question whose answer many ultimately have practical applications in agriculture and plant breeding. The proposed studies will provide a basic understanding of the genes involved in sex determination, and will also be of value in understanding how plant cells are coordinated to maintain a single sexual developmental fate, and how the sexual developmental fate of cells within an organism can change to adapt to changes in the environment. ***
