Functional analysis of non-ribosomal peptide synthetases (NRPSs) in Trichoderma virens reveals a polyketide synthase (PKS)/NRPS hybrid enzyme involved in the induced systemic resistance response in maize

• Published in: Microbiology (Society for General Microbiology) Vol. 158; no. Pt 1; pp. 155 - 165
• Main Authors: Mukherjee, Prasun K, Buensanteai, Natthiya, Moran-Diez, Maria E, Druzhinina, Irina S, Kenerley, Charles M
• Format: Journal Article
• Language: English
• Published: England 01.01.2012
• Subjects: Hypocrea virens; Molecular Sequence Data; Peptide Synthases - genetics; Peptide Synthases - metabolism; Phylogeny; Plant Proteins - genetics; Plant Proteins - immunology; Trichoderma - classification; Trichoderma - enzymology; Trichoderma - genetics; Trichoderma - growth & development; Zea mays; Zea mays - genetics; Zea mays - immunology; Zea mays - microbiology
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.052159-0

Trichoderma virens genome harbours genes encoding 22 non-ribosomal peptide synthetases (NRPSs) with at least one complete module (containing adenylation, thiolation and condensation domains) and four PKS/NRPS (polyketide synthase/NRPS) hybrid enzymes. After a primary screen for expression of these 26 genes when mycelia of T. virens are in contact with maize roots, seven genes that are upregulated were selected for further study. Using homologous recombination, loss-of-function mutants in six of these were obtained (the seventh, tex2, was acquired from our previous studies). Plant assays in a hydroponics system revealed that all seven mutants retained the ability to internally colonize maize roots. However, a mutation in one of the PKS/NRPS hybrid genes impaired the ability of T. virens to induce the defence response gene pal (phenylalanine ammonia lyase), suggesting a putative role for the associated metabolite product in induced systemic resistance. Interestingly, the mutant retained its ability to induce another defence response gene aos (allene oxide synthase). We thus provide evidence that a PKS/NRPS hybrid enzyme is involved in Trichoderma-plant interactions resulting in induction of defence responses.