DelsGate: a robust and rapid method for gene deletion.

Gene deletion is one of the most powerful tools to study gene function. In the genomics era there is great demand for fast, simple high-throughput methods for gene deletion to study the roles of the large numbers of genes that are being identified. Here we present an approach that speeds up the process of generation of deletion mutants by greatly simplifying the production of gene deletion constructs. With this purpose we have developed a method, which we named DelsGate (Deletion via Gateway), that combines PCR and Gateway cloning technology together with the use of the I-SceI homing endonuclease to generate precise deletion constructs in a very simple, universal and robust manner in just 2 days. DelsGate consists of standard PCR of only the 5' and 3' 1 kb gene flanks directly followed by in vitro Gateway cloning and final generation of the circular deletion construct by in vivo recombination in Escherichia coli. For use in DelsGate we have modified a Gateway cloning vector to include selectable markers for the transformation of Ascomycetes and the Basidiomycete fungus Ustilago maydis. The PCR and transformation steps of DelsGate should be well suited for high-throughput approaches to gene deletion construction in fungal species. We describe here the entire process, from the generation of the deletion construct with DelsGate to the analysis of the fungal transformants to test for gene replacement, with the Basidiomycete fungus Ustilago maydis. Application of DelsGate to other fungal species is also underway. Additionally, we describe how this basic approach can be adapted to other genetic manipulations with minor changes. We specifically describe its application to create unmarked deletions in Ralstonia solanacearum, a Gram-negative phytopathogenic bacterium.