Characterisation and heterologous biosynthesis of burnettiene A, a new polyene-decalin polyketide from Aspergillus burnettii

Chemical exploration of the recently described Australian fungus, , uncovered a new metabolite, burnettiene A. Here, we characterise the structure of burnettiene A as a polyene-decalin polyketide. Bioinformatic analysis of the genome of identified a putative biosynthetic gene cluster for burnettiene A ( ), consisting of eight genes and sharing similarity to the fusarielin gene cluster. Introduction of the reassembled gene cluster into for heterologous expression resulted in the production of burnettiene A under native promoters. Omission of encoding a cytochrome P450 led to the production of preburnettiene A, confirming that BueE is responsible for catalysing the regiospecific multi-oxidation of terminal methyl groups to carboxylic acids. Similarly, was shown to encode an ester-forming methyltransferase, with its omission resulting in the production of the tricarboxylic acid, preburnettiene B. Introduction of an additional copy of the transcription factor under the regulation of the promoter significantly improved the heterologous production of the burnettienes. Burnettiene A displayed strong cytotoxicity against mouse myeloma NS-1 cells (MIC 0.8 μg mL ).