Chemical Ecogenomics-Guided Discovery of Phytotoxic alpha-Pyrones from the Fungal Wheat Pathogen Parastagonospora nodorum

A biosynthetic gene cluster that is significantly upregulated in the fungal wheat pathogen Parastagonospora nodorum during plant infection was reconstructed heterologously in Aspergillus nidulans. This led to the discovery of five new alpha-pyrone polyketides, alternapyrones B-F (2-6). Compounds 5 and 6, which contain a highly substituted dihydrofuran, exhibited phytotoxicity on wheat seed germination. It is demonstrated that only three enzymes, one highly reducing polyketide synthase and two multifunctional P450 oxygenases, are needed to synthesize the structurally complex products.