Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/3/2011
Publication Date: 12/3/2011
Citation: Malmierca, M.G., Hermosa, R., Alexander, N.J., Mccormick, S.P., Proctor, R., Rumbero, A., Monte, E., Gutierrez, S., Cardoza, R.E. 2011. Identification of a trichothecene gene cluster and description of the harzianum A biosynthesis pathway in the fungus Trichoderma arundinaceum. Meeting Abstract. PS6:51. Interpretive Summary:
Technical Abstract: Trichothecenes are sesquiterpenes that act like mycotoxins. Their biosynthesis has been mainly studied in the fungal genera Fusarium, where most of the biosynthetic genes (tri) are grouped in a cluster regulated by ambient conditions and regulatory genes. Unexpectedly, few studies are available about trichothecene production by other fungal genera like Myrothecium or Trichoderma. The aim of this work is to determine the presence of a tri gene cluster in Trichoderma arundinaceum (produces harzianum A) and to functionally characterize some of the genes involved in the harzianum A pathway. A genomic library was constructed and positive clones were selected by hybridization with tri gene probes from Fusarium and Myrothecium. The cluster region was sequenced using a genome walking strategy. By precursor feeding experiments and heterologous expression in yeast of tri5, tri4, and tri11 genes and the later identification of the final compound by GC-MS, we propose the harzianum A biosynthesis pathway. Thus, we describe a tri gene cluster in T. arundianceum that encodes a trichothecene efflux pump (tri12). The harzianum A biosynthesis starts with the cyclization of farnesyl pyrophosphate to trichodiene by TRI5, this compound is then hydroxylated at 3 different positions by TRI4 and once more by TRI11 to get trichodermol. The putative final step is the C-4 acetylation of trichodermol by TRI3. Thus, we demonstrate the presence of a tri gene cluster in Trichoderma but, unexpectedly, gene organization and orientation are very different from those described for fusarium.The main differences are 1) tri5 is located outside the main cluster; 20 TRI4 hydroxylates the trichodiene 3 times (4 in Fusarium) adn 3) TRI11 hydroxylates the trichothecene skeleton in C-4 (C-15 in Fusarium).