MADS-box genes encode DNA-binding regulatory proteins that play key roles in plant and animal development. In plants, MADS-box genes regulate flower-meristem and flower-organ identity, and Dr. Yanofsky's prior studies have led to the isolation and initial characterization of many members of the Arabidopsis MADS-box gene family. In the current proposal, he plans to extend his descriptive studies to the functional level where he will focus on mutant alleles of three of these genes involved in gynoecium and fruit development. The AGL8 gene is required for normal carpel and fruit development since agl8 mutants display severe fruit abnormalities. In addition, AGL8 plays a redundant role, together with the APETALA1 and CAULIFLOWER genes, during flower initiation. A series of molecular and genetic experiments are planned to investigate the interaction between AGL8 and other genes controlling fruit and carpel development as well as the early step of flower initiation. These studies should provide significant insights into the functions of AGL8 and will allow Dr. Yanofsky to integrate its role into emerging models for flower initiation and carpel- and ovule-development. Dr. Yanofsky has identified a single targeted disruption event by homologous recombination in an initial population of 750 transgenic lines. Although this clearly demonstrates the feasibility of this procedure, the frequency of such an event has yet to be determined. This is particularly important since, if the frequency is roughly 10-(, then this already represents a rapid means of creating knockin and knockout mutations in their normal genomic context. If, however, the frequency is significantly lower, then improvements in transformation and/or selection strategies will be needed. Dr. Yanofsky will extend our successful efforts to use homologous recombination as a tool. Dr. Yanofsky will generate, constructs, and transgenic plants in an attempt to disrupt three additional MADS-box genes, including AGL4, AGL15, and AGL20.
