One step modification of Chlamydomonas reinhardtii BACs using the RED/ET system

With the availability of the complete genome, Chlamydomonas BACs are being used extensively in functional genomics analysis. The following aspects of their construction, however, make them less than optimal for some types of analysis. (1) These BACs do not contain a gene to allow direct selection of transformants in complementation analysis. (2) Co-transformation using the BAC and an independent vector with a selectable marker has a low efficiency. (3) Most BACs have more than one gene, necessitating sub-cloning of each gene into a different vector (relying on the use of restriction enzymes). To simplify this process, we modified Chlamydomonas BACs by inserting 2 selectable marker cassettes, using the RED-ET system. We ligated a eukaryotic and a prokaryotic selectable marker cassette and used it in a one-step modification instead of a two-step counter selection protocol and showed the expression of both cassettes. This method will decrease the time needed for use of BACs in functional genomics analysis in Chlamydomonas