Multiple families of peptide synthetase genes from ergopeptine-producing fungi

Abstract

Several eukaryotic and prokaryotic micro-organisms produce small, biologically active peptides on multifunctional nonribosomal peptide synthetases. These peptide synthetases consist of series of similar peptide synthetase domains; each domain is hypothesized to perform reactions required for the incorporation of one of the constituent amino acids into the peptide. I investigated the peptide synthetase gene families of two plant-associated fungi, Acremonium coenophialum and Claviceps purpurea, that produce ergopeptine alkaloids. Ergopeptines are the products of a peptide synthetase, one of several peptide synthetases likely to be produced by these fungi. Degenerate oligonucleotides based on conserved amino acid residues in previously analysed peptide synthetases were used to prime the amplification of DNA from A. coenophialum and C. purpurea. Analyses of the deduced products of various clones showed that four different fragments of A. coenophialum DNA and three different fragments of C. purpurea DNA encoded peptide synthetase domains similar to those from other micro-organisms. Hybridization analyses indicated that the four fragments cloned from A. coenophialum represented three different peptide synthetase genes, most of which were present in multiple copies in the genome of this fungus. Each of the three clones from C. purpurea appears to be from a different peptide synthetase gene, only one of which is duplicated. One clone from A. coenophialum hybridizes with DNA from C. purpurea, making it a good candidate for involvement in ergopeptine production. The results of this study indicate that ergopeptine-producing fungi have multiple families of peptide synthetase genes. The data also demonstrate the feasibility of isolating fragments of peptide synthetase genes with a PCR-based approach.