Acurin A, a novel hybrid compound, biosynthesized by individually translated PKS- and NRPS-encoding genes in Aspergillus aculeatus

• Published in: Fungal genetics and biology 2020-06, Vol.139, p.103378-103378, Article 103378
• Main Authors: Wolff, Peter B., Nielsen, Maria L., Slot, Jason C., Andersen, Lasse N., Petersen, Lene M., Isbrandt, Thomas, Holm, Dorte K., Mortensen, Uffe H., Nødvig, Christina S., Larsen, Thomas O., Hoof, Jakob B.
• Format: Article
• Language: English
• Subjects: Acurin A; Aspergillus aculeatus; CRISPR/Cas9; Hybrid compound; NRPS; PKS; Secondary metabolism
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1016/j.fgb.2020.103378

•A biosynthetic gene cluster for the hybrid polyketide-nonribosomal peptide compound acurin A in Aspergillus aculeatus.•The PKS and NRPS responsible for acurin A production are two individually transcribed entities.•Phylogenetics suggest that the separated PKS and NRPS is a result from the fission of an ancestral PKS-NRPS hybrid.•The biosynthetic capacity of A. aculeatus is facilitated by the use of CRISPR/Cas9 gene editing. This work presents the identification and proposed biosynthetic pathway for a compound of mixed polyketide-nonribosomal peptide origin that we named acurin A. The compound was isolated from an extract of the filamentous fungus Aspergillus aculeatus, and its core structure resemble that of the mycotoxin fusarin C produced by several Fusarium species. Based on bioinformatics in combination with RT-qPCR experiments and gene-deletion analysis, we identified a biosynthetic gene cluster (BGC) in A. aculeatus responsible for the biosynthesis of acurin A. Moreover, we were able to show that a polyketide synthase (PKS) and a nonribosomal peptide synthetase (NRPS) enzyme separately encoded by this BGC are responsible for the synthesis of the PK-NRP compound, acurin A, core structure. In comparison, the production of fusarin C is reported to be facilitated by a linked PKS-NRPS hybrid enzyme. Phylogenetic analyses suggest the PKS and NRPS in A. aculeatus resulted from a recent fission of an ancestral hybrid enzyme followed by gene duplication. In addition to the PKS- and NRPS-encoding genes of acurin A, we show that six other genes are influencing the biosynthesis including a regulatory transcription factor. Altogether, we have demonstrated the involvement of eight genes in the biosynthesis of acurin A, including an in-cluster transcription factor. This study highlights the biosynthetic capacity of A. aculeatus and serves as an example of how the CRISPR/Cas9 system can be exploited for the construction of fungal strains that can be readily engineered.