XVI International Botanical Congess

The discovery of an active RecA homolog in higher plant chloroplasts points to a role of recombination in the metabolism of chloroplast DNA. A crucial component of the recombination process is the resolution of the four-stranded Holliday junction by an endonuclease that specifically recognizes the structural features of this intermediate. Using a synthetic Holliday junction we have found a resolving activity in soybean chloroplast extracts which yields specific cleavage products. We have detected homologous recombination in vitro between two identical plasmids with non-overlapping deletions in an antibiotic resistance marker, after transformation of E. coli. We have characterized some of the recombinant products of the in vitro recombination assay and are in the process of developing a physical in vitro assay to study the recombination products directly.