Intra- and intermolecular site-specific recombination in plant cells mediated by bacteriophage P1 recombinase.

A site-specific recombination system has many potential uses for rearranging genetic material in higher eukaryotic cells: for example, the control of gene expression by deletion or inversion of DNA segments, the clustering of transgenic constructs via site-specific integration, and the generation of chromosomal translocations. In this report, we describe a first step towards the application of a site-specific recombination system in plant cells. By use of a transient assay, we demonstrate that the bacteriophage P1 cre gene can be expressed as a functional recombinase in tobacco cells. Upon expression in tobacco protoplasts, Cre recognizes its target sites, lox, and mediates reciprocal genetic crossovers at these sites. When the lox sites are present in cis to one another, and arranged in either direct or inverted orientations, we detect Cre/lox-specific deletion and inversion events, respectively. The placement of lox sites in trans resulted in the co-integration of the substrates by Cre-mediated intermolecular recombination. These results indicate that the Cre/lox site-specific recombination system might be further developed as an additional tool for manipulating DNA in plant cells. Applications relevant to the genetic engineering of higher plants are discussed.