Secondary metabolite biosynthetic genes often occur in clusters that tend to be sub-telomerically located and are coordinately regulated under certain laboratory conditions [18–20]. Typically, a secondary metabolite biosynthetic gene cluster contains NVP-LDE225 chemical structure a gene encoding one of several key “backbone” enzymes of the secondary metabolite biosynthetic process: a polyketide synthase (PKS), a non-ribosomal peptide synthetase (NRPS), a polyketide synthase/non-ribosomal peptide synthetase
hybrid (PKS-NRPS), a prenyltransferase known as dimethylallyl tryptophan synthase (DMATS) and/or a diterpene synthase (DTS). Comparative sequence analysis based on known backbone enzymes has been used to identify potential secondary metabolite biosynthetic gene clusters for subsequent experimental verification. One approach for experimental verification is
the deletion of genes with suspected roles in secondary metabolite biosynthesis followed by identification of the specific secondary metabolite profiles of the mutants by thin layer chromatography, NMR or other methods [7, 8]. For example, the deletion of A. fumigatus encA, which encodes an ortholog of the A. nidulans non-reducing PKS (NR-PKS) mdpG, followed by analysis of culture extracts using high-performance liquid chromatography (HPLC) enabled the recent identification of endocrocin and its biosynthetic pathway intermediates . Similarly, FK866 molecular weight the deletion selleck chemical of the gene encoding the PKS, easB, enabled the identification of the emericellamide biosynthetic pathway of A. nidulans. Another approach is the overexpression of predicted transcriptional regulators of secondary metabolism gene clusters with subsequent analysis of the gene expression and
secondary metabolite profiles of the resulting strains, which has facilitated the identification of numerous secondary metabolites and the genes responsible for their synthesis [23, 24]. For example, overexpression of laeA in A. nidulans, a global transcriptional regulator of secondary metabolism production, coupled with microarray analysis, facilitated the delineation of the cluster responsible for production of the anti-tumor compound, terrequinone A . Thus, genome sequence analysis, coupled with targeted experimentation, has been a highly effective strategy for identifying novel secondary metabolites and the genes involved in their synthesis. The Aspergillus Genome Database (AspGD; http://www.aspgd.org) is a web-based resource that provides centralized access to gene and protein sequences, analysis tools and manually curated information derived from the published scientific literature for A. nidulans, A. fumigatus, A.