Transient transformation of the rust fungus Puccinia graminis f. sp. tritici

The biotrophic rust fungus Puccinia graminis f sp. tritici (Pgt) was transformed by particle bombardment. The promoter from the Pgt translation elongation factor 1 alpha(EF-1 alpha) gene was fused to the bacterial marker genes hygromycin B phosphotransferase (hpt) and beta-glucuronidase (CUS). Transformation constructs were introduced into uredospores of Pgt, an obligate pathogen of wheat, by biolistic bombardment. Uredospores transformed with the construct containing the hpr gene germinated and initiated branching on selective medium, indicating that they had acquired resistance to hygromycin B. However, transformants stopped growing 5 days after bombardment. CUS activity in uredospores and germlings was histochemically detected 4-16 h after bombardment. CUS expression was also obtained using the INF24 promoter from the bean rust fungus Uromyces appendiculatus, demonstrating that heterologous genes can be expressed in P. graminis under the control of regulatory sequences from closely related organisms.