Towards a more complete genetic mapping of the secondary metabolism in A. nidulans, we first cultivated a reference strain on an array of different growth media to uncover polyketides that were not previously linked to a gene cluster. This analysis revealed several compounds, including austinols, violaceols, arugosins and prenylated xanthones. Next, genetic links to these compounds were established by constructing and screening an A. nidulans mutant library

containing individual deletions of 32 putative PKS genes. The A. nidulans strain IBT29539 (argB2, pyrG89, veA1, nkuAΔ) (Nielsen et al., 2008) was used as the reference strain and for deletion-strain constructions. Escherichia coli strain DH5α was used for cloning. Fungal minimal Selleckchem Selumetinib medium (MM) was as described in Cove (1966), but with 1% glucose, 10 mM NaNO3 and 2% agar. Medium

for alcA promoter induction consisted of MM supplemented with 100 mM l-threonine and 100 mM glycerol as carbon source instead of 1% glucose. Polyketide screening media variants CYA, CYAs, YES and RT were prepared as per Frisvad & Samson (2004). CY20 medium consisted of CYA with 170 g sucrose; RTO contained RT with 30 g organic oat meal; and YE was made as YES but without sucrose. All media variants were supplemented with 10 mM uridine, 10 mM uracil and/or 4 mM l-arginine where appropriate. Individual PKS gene deletions were carried out as described previously (Nielsen et al., 2006), except that IDH activation the targeting fragments were assembled using Gateway technology (Hartley et al., 2000) (see Table S1 for PCR oligonucleotide and Fig. S2 for an overview of the procedure). The A. nidulans transformants were streak

purified and rigorously screened through three complementing diagnostic PCRs. Subsequently, the Aspergillus fumigatus pyrG marker was eliminated from all strains by selecting on 5-fluoroorotic acid medium before final verification by two additional complementing Nitroxoline diagnostic PCRs (see Fig. S3 and Table S2). All strains have been deposited in the IBT strain collection, DTU, (http://www.fbd.dtu.dk/straincollection/). The amino acid substitution of serine to alanine, S1660A, in ausA (AN8383) was created by USER fusion (Geu-Flores et al., 2007) according to the method described by Hansen et al. (2011). The allele was transferred to IBT29539 and the pyrG marker was eliminated by direct repeat recombination, creating strain IBT31032 containing only the desired point mutation. The strain was verified to contain the ausA-S1660A allele by sequencing (StarSEQ, Germany). See Table S3 for primer details. The gene, ausA, was PCR amplified by USER fusion (Geu-Flores et al., 2007) and inserted into both pU1111-1 and pU1211-1 (Hansen et al., 2011) creating pDH23 (gpdA promoter) and pDH24 (alcA promoter), respectively.