|Cardoza, Rosa Elena|
Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2013
Publication Date: 4/1/2013
Citation: Malmierca, M.G., Cardoza, R., Alexander, N.J., McCormick, S.P., Collado, I.G., Hermosa, R., Monte, E., Gutierrez, S. 2013. Relevance of trichothecenes in fungal physiology: Disruption of tri5 in Trichoderma arundinaceum. Fungal Genetics and Biology. 53(2013):22-33. Interpretive Summary: Some trichothecenes, produced by fungi that infect crop plants, are toxic to plants and can be harmful to the health of humans or animals that consume food or feed prepared from infected grain. Other trichothecenes, such as those produced by the biocontrol fungus Trichoderma arundinaceum, are toxic to harmful fungal pathogens but not to plants. In this research, we found that blocking the production of the trichothecene, harzianum A (HA) in T. arundinaceum, reduces but does not eliminate its ability to control fungal pathogens of plants. This research provides scientists with the tools to identify other factors that are important in biocontrol of other fungi and to understand the interactions between these factors and trichothecenes. Knowledge of genetic control of trichothecene metabolism may aid in designing safe and effective biocontrol organisms to use against plant fungal diseases.
Technical Abstract: Trichothecenes are sesquiterpenoid mycotoxins produced mainly by Fusarium species. Harzianum A (HA), a non-phytotoxic trichothecene produced by Trichoderma arundinaceum, has recently been found to have antagonistic activity against fungal plant pathogens and to induce plant genes involved in defense responses. In the present work, we have shown that disruption of the T. arundinaceum tri5 gene, which encodes a terpene synthase, stops the production of HA, alters the expression of other tri genes involved in HA biosynthesis, and alters the expression of the hmgR, dpp1, erg9, erg1, and erg7, all genes involved in terpene biosynthetic pathways. An increase in the level of ergosterol biosynthesis was also observed in the tri5 disrupted transformant in comparison with the wild type strain. The loss of HA also resulted in a drastic reduction of the biocontrol activity of the transformants against the phytopathogenic fungi Botrytis cinerea and Rhizoctonia solani. Finally, the effect of tri5 gene disruption on the regulation and balance of intermediates in terpene biosynthetic pathways, as well as the hypothetical physiological role of trichothecenes, both inter- and intracellularly, on regulation and biocontrol, are discussed.