To investigate whether the putative bue cluster contains all the genes required for the biosynthesis of 1, we employed a heterologous expression approach using A. nidulans LO8030. As A. nidulans LO8030 has a minimal metabolic background, it would facilitate downstream compound isolation compared to the complex metabolic profile of A. burnettii. We used multimarker AMA1-based fungal vectors (pYFAC) for expression, which facilitate combinatorial evaluation of gene cluster products. As 1 is actively produced by A. burnettii MST-FP2249, we built vectors containing the bue genes under their native regulatory sequences. We built a pYFAC-pyrG vector containing an 18-kb region that encodes bueA/B/C/D/E/R, and a pYFAC-riboB vector containing bueF (Fig. ). In the related fusarielin BGC, overexpression of the TF FSL7 leads to an increased fusarielin titre in its native host. To evaluate if the titres of 1 could be increased by TF overexpression in a heterologous host context, we constructed a pYFAC-pyroA vector encoding the TF bueR under the strong constitutive promoter gpdA (PgpdA), and additionally included the transporter gene bueG (Fig. ).