Recombination in the Plant Genome and its Application in Biotechnology

Abstract

Genetic variation within and between species is based on recombination of DNA molecules. Recombination also plays a very important role in the repair of damaged DNA. Clarity about the mechanism by which recombination occurs is of profound interest not only to understand how this process assures the maintenance of genome integrity and at the same time is the driving force of evolution, but also for its application in biotechnology. The isolation of genes involved in recombination and the elucidation of the role of many of the corresponding gene products in Escherichia coli and Saccharomyces cerevisiae has formed the basis for comparative analysis in other, more complex eukaryotic systems. The identification of homologous genes from different organisms, including plants, suggests a conservation of the general mechanisms of recombination. Transgenes introduced in an organism may be incorporated in the genome by either homologous or nonhomologous recombination (end joining). The preferred pathway differs strongly between organisms. In plants there is a preference for random integration of the introduced DNA by nonhomologous recombination, which might lead to the accidental inactivation of important genes and to variable and unpredictable expression of the transgene itself. Therefore, there is an urgent need for the development and improvement of techniques for the directed integration of transgenes at specific locations in the genome. The integration of transgenes by homologous recombination would allow specific modification or disruption of endogenous genes, providing a tool for more detailed analysis of gene function. In combination with the recent introduction of site-specific recombination systems from E. coli or yeast into plants, this may lead to the development of versatile systems for modification of the plant genome.