|TAYLOR, JAMES - Texas A&M University|
|MUKHERJEE, PRASUN - Bhabha Atomic Research Centre|
|DIXIT, KARUNA - Texas A&M University|
|IGUMENOVA, TATYANA - Texas A&M University|
|HORWITZ, BENJAMIN - Israel Institute Of Technology|
|KENERLEY, CHARLES - Texas A&M University|
Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2020
Publication Date: 7/18/2020
Citation: Taylor, J.T., Mukherjee, P.K., Puckhaber, L.S., Dixit, K., Igumenova, T.I., Suh, C.P., Horwitz, B.A., Kenerley, C.M. 2020. Deletion of the Trichoderma virens NRPS, Tex7, induces accumulation of the anti-cancer compound heptelidic acid: novel regulation of terpene biosynthesis by a non-ribosomal peptide synthetase. Biochemical and Biophysical Research Communications. 529:672-677. https://doi.org/10.1016/j.bbrc.2020.06.040.
Interpretive Summary: Trichoderma virens is a beneficial plant fungus that triggers maize plants to produce defensive compounds that help protect plants from the foliar disease known as southern corn leaf blight. This beneficial fungus has been separated into two strains, referred to as P- and Q-strains, based on the production of heptelidic acid (also known as kongenic acid) which has been shown to have antibiotic and anticancer properties; only P-strains are reported to produce heptelidic acid. While identifying compounds produced by a Q-strain of T. virens, we purposely disrupted a gene cluster known as Tex7 to determine what compounds were regulated or produced by the cluster. Unexpectedly, the disruption of the Tex7 gene cluster caused the Q-strain to produce abundant quantities of heptelidic acid. This discovery may provide a more efficient means of generating heptelidic acid and suggest that the strain classification structure of T. virens may have to be revisited. Our findings also revealed that the mutated Q-strain inhibited growth of maize seedlings, but still caused plants to produce defensive compounds to help protect plants against the southern corn leaf blight disease.
Technical Abstract: The anticancer antibiotic heptelidic acid is a sesquiterpene lactone produced by the beneficial plant fungus Trichoderma virens. This species has been separated into two strains, referred to as P and Q, based on its biosynthesis of secondary metabolites; notably, only P-strains were reported to produce heptelidic acid. While characterizing a Q-strain of T. virens containing a directed mutation in the non-ribosomal peptide synthetase encoding gene Tex7, the appearance of an unknown compound in anomalously large quantities was visualized by TLC. Using a combination of HPLC, LC-MS/MS, and NMR spectroscopy, this compound was identified as heptelidic acid. This discovery alters the strain classification structure of T. virens. Additionally, the Tex7 mutants inhibited growth of maize seedlings, while retaining the ability to induce systemic resistance against the foliar fungal pathogen, Cochliobolus heterostrophus.