Genome-wide analyses of Fusarium fujikuroi reveal complex regulation of secondary metabolism and new metabolites
Fusarium fujikuroi is a biotechnologically important fungus due to its almost unique ability to produce gibberellic acids (GAs), a family of phytohormones. The fungus was described about 100 years ago as the causative agent of Bakanae (“foolish seedling”) disease of rice. Apart from GAs, the fungus is known to produce pigments and mycotoxins, but the biosynthetic genes are known for only eight products. Here we present a high-quality genome sequence of the first member of the Gibberella fujikuroi species complex (GFC) that allowed de novo genome assembly with 12 scaffolds corresponding to the 12 chromosomes. In this work we focused on identification of all potential secondary metabolism-related gene clusters and their regulation in response to nitrogen availability by transcriptome, proteome, HPLC-FTMS and ChIP-seq analyses. We show that most of the cluster genes are regulated in a nitrogen-dependent manner, and that expression profiles fit to proteome and ChIP-seq data for some but not all clusters. Comparison with genomes of all available Fusarium species, including the recently sequenced F. mangiferae and F. circinatum, showed only a small number of common gene clusters and provides new insights into the divergence of secondary metabolism in the genus Fusarium. Phylogenetic analyses suggest that some gene clusters were acquired by horizontal gene transfer, while others were present in ancient Fusarim species and have evolved differently by gene duplications and losses. One polyketide synthase (PKS) and one non-ribosomal peptide synthetase (NRPS) gene cluster are unique for F. fujikuroi. Their products were identified by combining overexpression of cluster genes with HPLC-FTMS-based analyses. In planta expression studies suggest a specific role of the PKS19 product in rice infection. Our results indicate that comparative genomics together with the used genome-wide experimental approaches is a powerful tool to uncover new secondary metabolites and to understand their regulation at the transcriptional, translational and epigenetic levels. Overall design: Examination of 3 different histone modifications, with 2 growth conditions for one of the modifications (Total of 4 samples)