This proposal seeks to analyze the initiation and organization of lateral root meristems in radish (Raphanus sativus) where large numbers of meristems can be induced to develop synchronously and rapidly. By analysing patterns of protein profiles generated by in vitro translation we will determine times at which to produce cDNA libraries from which to isolate probes for genes that are expressed uniquely or preferentially in a staqe-specific manner in the organizing meristems. These probes will then be used to examine the tissue and cellular location of gene products, and to examine whether homologous genes are expressed in other types of meristems, such as the shoot apical meristem, or in meristems of other species. Our experiments will be aided by the use of primordiomorphs formed in gamma plantlets or by colchicine treatment. Primordiomorphs are meristems formed in the absence of cell division, and in them we will be able to examine the relationship between molecular genetic events and a requirement for cell divisions at specific stages of meristem initiation and organization. Apical meristems are initiated in the embryo of vascular plants and function directly, or indirectly through the formation of other meristems, to produce the entire post-embryonic organism. The initiation and organization of meristem function in localized groups of cells at specific sties is a major event in establishing the patterns of plant development. Little is known of the molecular genetic events that control the developmental pathway of meristem formation, or how these events are related to observable chanages in cellular and tissue structure.
