9506258 Poethig The correct timing of events in development is critical for normal morphogenesis. At the same time, changes in the relative timing of different developmental events (heterochrony) can be an important source of novelty in evolution, particularly when the timing of reproductive maturity changes relative to somatic maturity. The vegetative development of the shoot in plants is marked by several more or less discrete phases that can be distinguished from one another on the basis of a variety of morphological and physiological traits. A large number of obvious phase specific traits have been defined in maize, greatly facilitating the genetic and molecular analysis of the process of phase change in this species. Recently, Dr. Poethig has identified a new mutation, glossy early flowering, that dramatically accelerates both vegetative and reproductive development. Mutant plants produce leaves with adult vegetative fates abnormally early in shoot development and also flower early. Although extensive work on woody plants has suggested that the vegetative phase of the shoot is linked in some way to its reproductive capacity, gef is the first genetic link between these two aspects of shoot development in maize. Dr. Poethig proposes to a) characterize the phenotype of gef at a molecular, histological, and morphological level, b) determine its cell autonomy by clonal analysis, and c) establish its relationship to other genes involved in phase change by analyzing double mutations. In addition, he proposes to conduct extensive genetic screens for new mutations affecting phase change. these screens will involve screening in a wild type genetic background for mutations that accelerate vegetative phase change, and screening a gl15-2 background for mutations that either enhance or suppress this partially functional mutation. These experiments should provide new insight into the relationship between vegetative and reproductive maturation in plants, and provide th e genetic and molecular resources necessary for future research on the mechanisms of this important aspect of plant development. ***
