possibly due to the presence of repetitive DNA elements. We therefore designed an advanced shuttle vector in the form of pBS–pds (Fig. 1) featuring all requirements of an advanced shuttle vector for co-transformation of at least two additional transgenes. Transformation frequency using this vector was up to twenty-fold higher than transformation with pPlat–pds (Table 2 and [37]). In addition, transformed strains displayed resistance due to introduction of the selection marker for long time periods (up to 33 months), indicating high nuclear stability of the developed vector