9506360 Zimmerman Essentially nothing is known about the molecular mechanisms nor the genes involved in regulating differentiation and morphogenesis during early embryogenesis in higher plants. This proposal describes the molecular and genetic analysis on one of the earliest stages of embryogenesis, the globular stage, Dr. Zimmerman has chosen this stage because it is during the globular stage that all of the basic tissue systems of the mature plant are initiated and the primary meristems are established. She has identified two globular defective Arabidopsis mutants that show interesting defects in development during the globular stage. One of these mutants may exhibit a homeotic transformation of one embryo cell type to another, and the other mutant shows defects in tissue organization and the transition to polarized growth. Each of these mutations appears to be caused by T-DNA insertion, and hence the genes of interest should be tagged; indeed, Dr. Zimmerman has already cloned one of the genes using T-DNA as a probe. She will use these mutants to address fundamental questions regarding the molecular basis for cellular identity, tissue differentiation and organization in plant embryogenesis. In order to begin to address these questions, she will 1) characterize the phenotype and timing of developmental interference in each mutant, 2) genetically map the mutations relative to known chromosomal markers and relative to other embryo defective genes, and in the longer term, 3) isolate and characterize the tagged genes responsible for the mutations in order to evaluate the molecular and developmental consequences of these mutations. ***
