9604489 Benfey The goal of this work is to understand the molecular mechanisms that regulate organogenesis in plants, here with a focus on root formation. A number of mutants have been collected from Arabidopsis which show altered division, expansion and maturation of root cells. The class of cell expansion mutants can itself be sub-divided into mutants that are affected by the environment and others that are autonomous of the environmental condition, but respond to internal (hormonal) cues. Other mutants of expansion shift from longitudinal to radial expansion. The work focuses on two mutants that are indicative of tow individual classes of modulated expansion growth, SABRE and COBRA. SABRE has been cloned. Experiments are designed to study hormonal and positional effects on the expression of the SABRE mutant phenotype, and functional studies of the gene products in transgenic assays. COBRA will be cloned by molecular complementation, a 56 kb region which contains the gene is in hand. The amount of the COBRA product will then be modulated to gauge its effect on the phenotype and, finally, additional mutants and suppresser mutations will be screened for. With this work, Dr. Benfey will initiate studies that integrate the developmental sequence of root cell expansion with a functional assay of the gene product and its positional and concentration effects. Work on the growth of plant root cells will contribute to our understanding of plant cell growth characteristics.
