The pBS–pds vectors harboring mutated pds have been designed to contain several unique restriction sites for insertion of transgenes (Fig. 1). Thus, a number of restriction sites, both at the 5′ and 3′ of the pds, allow insertion of additional transgenes for co-transformation using the mutated pds as selection marker (Fig. 1A). The unique restriction sites provided at both sides of both inserts facilitate extraction of the linear DNA cassette consisting of transgenes and the endogenous DNA marker (Fig. 1B).