Overexpressing Transcriptional Regulator in Aspergillus oryzae Activates a Silent Biosynthetic Pathway to Produce a Novel Polyketide

Abstract

Fungal genomes carry many gene clusters seemingly capable of natural product biosynthesis, yet most clusters remain silent. This places a major constraint on the conventional approach of cloning these genes in more amenable heterologous host for the natural product biosynthesis. One way to overcome this difficulty is to activate the silent gene clusters within the context of the target fungus. Here, we successfully activated a silent polyketide biosynthetic gene cluster in Aspergillus oryzae by overexpressing a transcriptional regulator found within the cluster from a plasmid. This strategy allowed us to isolate a new polyketide product and to efficiently decipher its biosynthetic pathway. Through this exercise, we also discovered unexpected activities of the biosynthetic enzymes found in the cluster. These results indicate that our approach would be valuable for isolating novel natural products and engineering analogues of comparable, if not more potent, bioactivity.

The re-emergence of natural products for drug discovery in the genomics era

“…Bacterial or fungal polyketides 125,129,153,[155][156][157] are chemically diverse and some have displayed antibiotic activity by inducing ribosomal frameshift errors 158 a strategy thought to avoid antibiotic resistance mechanisms 159 . However, owing to the intrinsic molecular complexity of polyketides, chemical synthesis is not commercially viable.…”

Comprehensive annotation of secondary metabolite biosynthetic genes and gene clusters of Aspergillus nidulans, A. fumigatus, A. niger and A. oryzae

“…Similarly, the deletion of the gene encoding the PKS, easB , enabled the identification of the emericellamide biosynthetic pathway of A. nidulans [22]. 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 [18].…”

Targeted Disruption of Transcriptional Regulators inChaetomium globosumActivates Biosynthetic Pathways and Reveals Transcriptional Regulator-Like Behavior of Aureonitol

“…Proposed biosynthetic pathways of (A) aureonitol(6) and mollipilin A (9) and B (10), (B) cochliodones 8 and 13, and (C) coarctatins 11 and 12.Journal of the American Chemical SocietyArticle dx.doi.org/10.1021/ja405128k | J. Am.…”