HORMONE-INDUCED SIGNALING DURING MOSS DEVELOPMENT.

Understanding how a cell responds to hormonal signals with a new program of cellular differentiation and organization is an important focus of research in developmental biology. In Funaria hygrometrica and Physcomitrella patens, two related species of moss, cytokinin induces the development of a bud during the transition from filamentous to meristematic growth. Within hours of cytokinin perception, a single-celled initial responds with changes in patterns of cell expansion, elongation, and division to begin the process of bud assembly. Bud assembly in moss provides an excellent model for the study of hormone-induced organogenesis because it is a relatively simple, well-defined process. Since buds form in a nonrandom pattern on cells that are not embedded in other tissues, it is possible to predict which cells will respond and where the ensuing changes will take place. In addition, bud assembly is amenable to biochemical, cellular, and molecular biological analyses. This review examines our current understanding of cytokinin-induced bud assembly and the potential underlying mechanisms, reviews the state of genetic analyses in moss, and sets goals for future research with this organism.