Overexpression of a three-gene conidial pigment biosynthetic pathway in Aspergillus nidulans reveals the first NRPS known to acetylate tryptophan

Fungal Genet Biol. 2017 Apr:101:1-6. doi: 10.1016/j.fgb.2017.01.006. Epub 2017 Jan 17.

Abstract

Fungal nonribosomal peptide synthetases (NRPSs) are megasynthetases that produce cyclic and acyclic peptides. In Aspergillus nidulans, the NRPS ivoA (AN10576) has been associated with the biosynthesis of grey-brown conidiophore pigments. Another gene, ivoB (AN0231), has been demonstrated to be an N-acetyl-6-hydroxytryptophan oxidase that putatively acts downstream of IvoA. A third gene, ivoC, has also been predicted to be involved in pigment biosynthesis based on publicly available genomic and transcriptomic information. In this paper, we report the replacement of the promoters of the ivoA, ivoB, and ivoC genes with the inducible promoter alcA in a single cotransformation. Co-overexpression of the three genes resulted in the production of a dark-brown pigment in hyphae. In addition, overexpression of each of the Ivo genes, ivoA-C, individually or in combination, allowed us to isolate intermediates and confirm the function of each gene. IvoA was found to be the first known NRPS to carry out the acetylation of the amino acid, tryptophan.

Keywords: Aspergillus nidulans; N-acetyltryptophan oxidase; Nonribosomal peptide synthetase (NRPS); Pigment biosynthesis; Tryptophan N-acetyltransferase.

MeSH terms

  • Aspergillus nidulans / enzymology
  • Aspergillus nidulans / genetics
  • Fungal Proteins / biosynthesis
  • Fungal Proteins / genetics
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Fungal
  • Monophenol Monooxygenase / genetics*
  • Multigene Family / genetics
  • Peptide Biosynthesis, Nucleic Acid-Independent / genetics*
  • Peptide Synthases / genetics*
  • Pigmentation / genetics*
  • Promoter Regions, Genetic
  • Spores, Fungal / genetics
  • Spores, Fungal / growth & development
  • Tryptophan / biosynthesis

Substances

  • Fungal Proteins
  • Tryptophan
  • N-acetyl-6-hydroxytryptophan oxidase
  • Monophenol Monooxygenase
  • Peptide Synthases
  • non-ribosomal peptide synthase