9724044 Gruissem The goal of this work is to develop a tractable protocol for gene targeting in higher plants through homologous DNA recombination. Although homologous recombination transgenes has been reported in the past, the frequency has been low. The work will use a novel procedure that has been developed by this laboratory, targeting one the RbcS gene family in Arabidopsis. A recombinant form of RbcS is first introduced randomly into the genome and this substrate is then used for recombination events during early development. The result of recombination between the introduced gene and a resident gene of the RbcS gene family can be detected by the activation of a transgenic reporter. Recombination events will be screened for, via reporter gene expression, at the seedling stage. Once this system has been developed, it will provide a tool for reverse genetics that has been extremely successful in micro-organisms in the past, while it has been missing in higher plants.