Multifactorial Induction of an Orphan PKS-NRPS Gene Cluster in Aspergillus terreus

Abstract

Mining the genome of the pathogenic fungus Aspergillus terreus revealed the presence of an orphan polyketide-nonribosomal-peptide synthetase (PKS-NRPS) gene cluster. Induced expression of the transcriptional activator gene adjacent to the PKS-NRPS gene was not sufficient for the activation of the silent pathway. Monitoring gene expression, metabolic profiling, and using a lacZ reporter strain allowed for the systematic investigation of physiological conditions that eventually led to the discovery of isoflavipucine and dihydroisoflavipucine. Phytotoxin formation is only activated in the presence of certain amino acids, stimulated at alkaline pH, but strictly repressed in the presence of glucose. Global carbon catabolite repression by CreA cannot be abolished by positive-acting factors such as PacC and overrides the pathway activator. Gene inactivation and stable isotope labeling experiments unveiled the molecular basis for flavipucine/fruit rot toxin biosynthesis.

Advances in Aspergillus secondary metabolite research in the post-genomic era

“…14 Based on this finding, Ku homologs in Aspergillus have been deleted with the effect of substantially improving homologous integration efficiency. This approach has been demonstrated in A. nidulans ( nkuAΔ ), 15 A. fumigatus (akuAΔ and akuB KU80 Δ ), 16,17 A. niger (kusAΔ ), 18 A. terreus (akuBΔ ), 19 and A. oryzae (ku70Δ and ku80Δ ). 20,21 Because correct gene targeting frequencies are somewhat lower in A. oryzae compared with other Aspergilli , an alternative method was developed in which a homolog of human DNA ligase IV ( ligD ) was disrupted.…”

Regulation of secondary metabolite production in the fungal tomato pathogen Cladosporium fulvum

“…Many gene clusters related to SM biosynthesis have been identified in the genomes of filamentous fungi, yet this genetic potential rarely translates into an equivalent known chemical diversity because most SM biosynthetic pathways remain cryptic during in vitro cultivation (Brakhage and Schroeckh, 2011;Chiang et al, 2011;Collemare et al, 2008;Gressler et al, 2011). Indeed, the potency and context-specific nature of SMs is such that their respective biosynthetic genes are tightly regulated by a complex and hierarchical network of regulatory proteins.…”

Functional analysis of non-ribosomal peptide synthetases (NRPSs) in Trichoderma virens reveals a polyketide synthase (PKS)/NRPS hybrid enzyme involved in the induced systemic resistance response in maize

“…Further studies, such as a mutational analysis of the catalytic domain would be necessary to ascertain whether the protein or the metabolite acts as an elicitor. The major hurdle in identifying the secondary metabolite catalysed by the Tex13 cluster is the very specific expression in the plant roots, which could be overcome by using the strategy of activating the cluster using novel genetic tools (Gressler et al, 2011;Brakhage & Schroeckh, 2011). Trichoderma NRPSs…”