Publications

• Establishment of the inducible Tet-On system for the activation of the silent trichosetin gene cluster in Fusarium fujikuroi.

  Janevska S., Arndt B., Baumann L., Apken L.H., Mauriz Marques L.M., Humpf H.U., Tudzynski B.

  The PKS-NRPS-derived tetramic acid equisetin and its <i>N</i>-desmethyl derivative trichosetin exhibit remarkable biological activities against a variety of organisms, including plants and bacteria, e.g., <i>Staphylococcus aureus</i>. The equisetin biosynthetic gene cluster was first described in ... >> More

  The PKS-NRPS-derived tetramic acid equisetin and its <i>N</i>-desmethyl derivative trichosetin exhibit remarkable biological activities against a variety of organisms, including plants and bacteria, e.g., <i>Staphylococcus aureus</i>. The equisetin biosynthetic gene cluster was first described in <i>Fusarium heterosporum</i>, a species distantly related to the notorious rice pathogen <i>Fusarium fujikuroi</i>. Here we present the activation and characterization of a homologous, but silent, gene cluster in <i>F. fujikuroi</i>. Bioinformatic analysis revealed that this cluster does not contain the equisetin <i>N</i>-methyltransferase gene <i>eqxD</i> and consequently, trichosetin was isolated as final product. The adaption of the inducible, tetracycline-dependent Tet-on promoter system from <i>Aspergillus niger</i> achieved a controlled overproduction of this toxic metabolite and a functional characterization of each cluster gene in <i>F. fujikuroi</i>. Overexpression of one of the two cluster-specific transcription factor (TF) genes, <i>TF22</i>, led to an activation of the three biosynthetic cluster genes, including the <i>PKS-NRPS</i> key gene. In contrast, overexpression of <i>TF23</i>, encoding a second Zn(II)₂Cys₆ TF, did not activate adjacent cluster genes. Instead, <i>TF23</i> was induced by the final product trichosetin and was required for expression of the transporter-encoding gene <i>MFS-T</i>. TF23 and MFS-T likely act in consort and contribute to detoxification of trichosetin and therefore, self-protection of the producing fungus. << Less

  Toxins 9:0-0(2017) [PubMed] [EuropePMC]

• Two related pyrrolidinedione synthetase loci in Fusarium heterosporum ATCC 74349 produce divergent metabolites.

  Kakule T.B., Sardar D., Lin Z., Schmidt E.W.

  Equisetin synthetase (EqiS), from the filamentous fungus Fusarium heterosporum ATCC 74349, was initially assigned on the basis of genetic knockout and expression analysis. Increasing inconsistencies in experimental results led us to question this assignment. Here, we sequenced the F. heterosporum ... >> More

  Equisetin synthetase (EqiS), from the filamentous fungus Fusarium heterosporum ATCC 74349, was initially assigned on the basis of genetic knockout and expression analysis. Increasing inconsistencies in experimental results led us to question this assignment. Here, we sequenced the F. heterosporum genome, revealing two hybrid polyketide-peptide proteins that were candidates for the equisetin synthetase. The surrounding genes in both clusters had the needed auxiliary genes that might be responsible for producing equisetin. Genetic mutation, biochemical analysis, and recombinant expression in the fungus enabled us to show that the initially assigned EqiS does not produce equisetin but instead produces a related 2,4-pyrrolidinedione, fusaridione A, that was previously unknown. Fusaridione A is methylated in the 3-position of the pyrrolidinedione, which has not otherwise been found in natural products, leading to spontaneous reverse-Dieckmann reactions. A newly described gene cluster, eqx, is responsible for producing equisetin. << Less

  ACS Chem. Biol. 8:1549-1557(2013) [PubMed] [EuropePMC]