This invention provides cyanobacteria as an alternative source of ahas and pdsgenes for plant transformations and for selectable marking. In particular, itprovides for cyanobacteria, for example, Synechocystis, as a source of genesencoding herbicide insensitive proteins, and elements of genes for control ofexpression in plastids. Nucleic acid fragments, both the acetolactate synthase(ahas) large subunit and the ahas small subunit, were found to provideherbicide resistance. Also, the present invention provides novel Synechocystismutant phytoene desaturase (PDS) gene conferring resistance to 4-fluoro-6-[(alpha,alpha,alpha,-trifluoro-m-tolyl)oxy]-picolinamide, a bleachingherbicide. The present invention provides improvements to method involvingcyanobacteria for the screening of compounds, including a new high-through-putprotocol that is a rapid and cost effective way to identify target site genes.
