Blasticidin-S deaminase, a new selection marker for genetic transformation of the diatom .

Most genetic transformation protocols for the model diatom rely on one of two available antibiotics as selection markers: Zeocin (a formulation of phleomycin D1) or nourseothricin. This limits the number of possible consecutive genetic transformations that can be performed. In order to expand the biotechnological possibilities for , we searched for additional antibiotics and corresponding resistance genes that might be suitable for use with this diatom. Among the three different antibiotics tested in this study, blasticidin-S and tunicamycin turned out to be lethal to wild-type cells at low concentrations, while voriconazole had no detectable effect on . Testing the respective resistance genes, we found that the blasticidin-S deaminase gene () effectively conferred resistance against blasticidin-S to . Furthermore, we could show that expression of did not lead to cross-resistances against Zeocin or nourseothricin, and that genetically transformed cell lines with resistance against Zeocin or nourseothricin were not resistant against blasticidin-S. In a proof of concept, we also successfully generated double resistant (against blasticidin-S and nourseothricin) cell lines by co-delivering the vector with a vector conferring nourseothricin resistance to wild-type cells.