Linear schemes of the plasmids used in this study: pX1M-Z, pX1N-Z, pX1M-Z-X2, pX1N-Z-X2 and pGLG61/HpXYL3. Expression cassettes prGAP-XYL1-trAOX, prGAP-XYL2-trXYL2 and prGAP-XYL3-trAOX are shown as white, gray and doted boxes, respectively. The modified version of XYL1 ORF is shown as black box. The zeocin resistance gene (Zeor) and geneticin resistance gene (APH), linked to an impaired constitutive gene promoter, encoding glyceraldehydephosphate dehydrogenase (GAP) are designated with the hatched lines. H. polymorpha LEU2 gene and the telomeric region (TEL188)  as an autonomously replicating sequence are shown as cross-hatched lines. Origin of replication ORI and ampicillin resistance gene (bla) – arrows. Restriction sites: P, Pst I; H, Hind III; S, Sac I; Sl, Sal I; B, Bam HI; ScII, Sac II; Xb, Xba I; RI, Eco RI; NdI, Nde I; N, Not I.