A major goal of maize developmental genetics is the identification and characterization of the genes that direct and regulate the morphogenesis of the embryo and the plant. The principal investigator and his coworkers have been characterizing embryo-lethal mutations in several genes that play essential roles in the normal morphogenesis of the embryo. A second project is aimed at characterizing two genes that regulate the development of the axillary meristems. A major goal of these projects is to investigate the cellular autonomy of mutant expression of these genes. This will be done by using x-rays to break a chromosome arm carrying the normal allele, thereby producing genetically mutant sectors in otherwise genetically normal immature embryos. Specially constructed stocks will be used so that the mutant sectors will be marked by a lack of color (anthocyanin) while the normal tissues will be colored. If the genetically mutant sectors are phenotypically mutant, then the expression is cell autonomous, but if the mutant sectors are phenotypically normal, then mutant expression is non-autonomous. Similar approaches will be used in studies on dominant mutants affecting mature plant traits. Finally, x-ray induced sectors will be used in normal embryos to examine cell lineages and cell fate in the developing maize embryo. The acquisition of the portable x-ray unit would be of extraordinary significance for the research. This is so because, instead of having to bring heavy pots containing the corn plants with their attached developing ears into a building containing an x-ray unit, the mobile unit can be used to irradiate ears in the field. As a result, it will be possible to increase the scope of this area of research by at least an order of magnitude.
