3 SELECTABLE MARKERS FOR TRANSFORMATION OF USTILAGO-MAYDIS

Although Ustilago maydis is readily amenable to molecular genetic expe rimentation, few antibiotic-resistance markers are available for DNA-m ediated transformation. This poses constraints on experiments involvin g targeted gene disruption and complementation. To address this proble m, we constructed vectors using one of three additional genes as domin ant selectable markers for transformation. Two genes, sat-1 (encoding streptothricin acetyltransferase) and Sh-ble (encoding a phleomycin-re sistance polypeptide), are of bacterial origin and have been engineere d for expression in Ustilago sp. The third gene encodes an allele of U . maydis beta-tubulin that confers resistance to the fungicide benomyl .