Peptide synthetase gene in Trichoderma virens

Trichoderma virens (synonym, Gliocladium virens), a deuteromycete fungus, s uppresses soilborne plant diseases caused by a number of fungi and is used as a biocontrol agent. Several traits that may contribute to the antagonist ic interactions of T. virens with disease-causing fungi involve the product ion of peptide metabolites (e.g., the antibiotic gliotoxin and siderophores used for iron acquisition). We cloned a 5,056-bp partial cDNA encoding a p utative peptide synthetase (Psy1) from T. virens using conserved motifs fou nd within the adenylate domain of peptide synthetases. Sequence similaritie s with conserved motifs of the adenylation domain, acyl transfer, and two c ondensation domains support identification of the Psy1 gene as a gene that encodes a peptide synthetase. Disruption of the native Psy1 gene through ge ne replacement was used to identify the function of this gene. Psy1 disrupt ants produced normal amounts of gliotoxin but grew poorly under low-iron co nditions, suggesting that Psy1 plays a role in siderophore production. Psy1 disruptants cannot produce the major T. virens siderophore dimerum acid, a dipetide of acylated N-delta-hydroxyornithine. Biocontrol activity against damping-off diseases caused by Pythium ultimum and Rhizoctonia solani was not reduced by the Psy1 disruption, suggesting that iron competition throug h dimerum acid production does not contribute significantly to disease supp ression activity under the conditions used.