Putative Polyketide Synthase and Laccase Genes for Biosynthesis of Aurofusarin in Gibberella zeae

Abstract

Mycelia of Gibberella zeae (anamorph, Fusarium graminearum), an important pathogen of cereal crops, are yellow to tan with white to carmine red margins. We isolated genes encoding the following two proteins that are required for aurofusarin biosynthesis from G. zeae: a type I polyketide synthase (PKS) and a putative laccase. Screening of insertional mutants of G. zeae, which were generated by using a restriction enzyme-mediated integration procedure, resulted in the isolation of mutant S4B3076, which is a pigment mutant. In a sexual cross of the mutant with a strain with normal pigmentation, the pigment mutation was linked to the inserted vector. The vector insertion site in S4B3076 was a HindIII site 38 bp upstream from an open reading frame (ORF) on contig 1.116 in the F. graminearum genome database. The ORF, designated Gip1 (for Gibberella zeae pigment mutation 1), encodes a putative laccase. A 30-kb region surrounding the insertion site and Gip1 contains 10 additional ORFs, including a putative ORF identified as PKS12 whose product exhibits about 40% amino acid identity to the products of type I fungal PKS genes, which are involved in pigment biosynthesis. Targeted gene deletion and complementation analyses confirmed that both Gip1 and PKS12 are required for aurofusarin production in G. zeae. This information is the first information concerning the biosynthesis of these pigments by G. zeae and could help in studies of their toxicity in domesticated animals.

The L-Type Calcium Ion Channel Cch1 Affects Ascospore Discharge and Mycelial Growth in the Filamentous FungusGibberella zeae(AnamorphFusarium graminearum)

“…This suggests that, while the ⌬cch1 mutant is competent in infecting and colonizing wheat, it may not be as capable as the wild type in defending its resources against competitors in the crop residue. One possible explanation may be the reduced expression of the polyketide synthase gene responsible for aurofusarin production (fg12040) (17,34,41). fg12040 showed a 16-fold reduction in transcript abundance in the ⌬cch1 mutant compared to the wild type during vegetative growth; this is of interest as rubrofusarin, a precursor to aurofusarin and also FIG.…”

Identification of a starter unit acyl-carrier protein transacylase domain in an iterative type I polyketide synthase

“…Notwithstanding, one can envision the SAT domain from other homologs being responsible for loading an acetyl starter, thereby providing a biochemical foundation for observation of the ''starter unit effect'' in classical isotopic labeling experiments of some fungal polyketides (37). Other known metabolites produced by similar PKS enzymes include the YWA1 naphthopyrone (11), where as few as 5 residues truncated from the N terminus destroy product formation (38); cercosporin (12) (39); and aurofusarin (13) (40). In the case of PKS4 in the production of bikaverin (14) (41) and the PKS in the production of emodinanthrone (5) (42), the genes encode extended N termini with predicted structural similarities to that of the MAT enzyme, but they lack the active-site Cys in the GXCXG motif of SAT domains.…”

Phylogenomic analysis of polyketide synthase-encoding genes in Trichoderma

“…The genomes of all three Trichoderma genomes encode PKS genes that group in the non-reducing fungal PKS clade I, which includes the genes associated with Fusarium graminearum aurofusarin (Frandsen et al, 2011;Kim et al, 2005;Malz et al, 2005), Fusarium fujikuroi bikaverin (Linnemannstöns et al, 2002;Wiemann et al, 2009) and Aspergillus spp. DHN melanin (Baker, 2008; Chiang et al, 2011;Jørgensen et al, 2011; Langfelder et al, 1998; Tsai et al, 1998Tsai et al, , 2001Watanabe et al, 1999Watanabe et al, , 2000.…”