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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC CONTROL OF FUSARIUM MYCOTOXINS TO ENHANCE FOOD SAFETY

Location: Bacterial Foodborne Pathogens & Mycology Research Unit

Title: Novel aspinolide production by Trichoderma arundinaceum with a potential role in Botrytis cinerea antagonistic activity and plant defense priming

Authors
item Malmierca, M -
item Barua, J -
item McCormick, Susan
item Izquierdo-Bueno, I -
item Cardoza, R -
item Alexander, Nancy
item Hermosa, R -
item Collado, I -
item Monte, E -
item Gutierrez, S -

Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2014
Publication Date: June 25, 2014
Citation: Malmierca, M.G., Barua, J., McCormick, S.P., Izquierdo-Bueno, I., Cardoza, R.E., Alexander, N.J., Hermosa, R., Collado, I.G., Monte, E., Gutierrez, S. 2014. Novel aspinolide production by Trichoderma arundinaceum with a potential role in Botrytis cinerea antagonistic activity and plant defense priming. Environmental Microbiology. DOI: 10.1111/1462-2920.12514.

Interpretive Summary: Some trichothecenes, produced by fungi that infect crops, are toxic to plants and can be harmful to the health of humans and animals that consume food or feed prepared from infected grain. A trichothecene, harzianum A (HA), produced by the biocontrol fungus Trichoderma arundinaceum, is toxic to other fungi but not to plants. HA helps Trichoderma to fight harmful plant pathogens and primes natural plant defenses to fungal attack. However, genetically blocking production of HA does not eliminate the ability of Trichoderma to control fungal pathogens. In this research, we found that when HA production is blocked, metabolism of the fungus is altered and a new metabolite, aspinolide C, is produced that also inhibits fungal pathogen growth and primes plant defenses, effectively compensating for the loss of HA. 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 trichothecenes and other metabolites may aid in designing safe and effective biocontrol organisms to use against plant fungal diseases.

Technical Abstract: Harzianum A (HA), a non-phytotoxic trichothecene produced by Trichoderma arundinaceum, has recently been described to have antagonistic activity against fungal plant pathogens and to induce plant defense genes. In the present work, we have shown that a tri5 gene-disrupted mutant (Ta'Tri5), which lacks HA production, overproduces two polyketides, aspinolides B and C, which were not detected in the wild type strain. In addition, four new aspinolides (D-G), produced in small amounts in the mutant, were characterized. These aspinolides seem to have a redundant function in the environmental interactions of T. arundinaceum and they may be responsible, at least a part, for the antifungal activity and the plant sensitization effect observed in tri5 disrupted transformant. In addition, the molecular changes involving virulence factors in the phytopathogenic fungus Botrytis cinerea 98 during interaction with T. arundinaceum were investigated. We have shown that the expression of genes involved in the production of botrydial by B. cinerea 98 is repressed by HA. The expression of other virulence genes of B. cinerea 98 is induced by the presence of T. arundinaceum, for example the atrB and pg1 that encode for an ABC transporter and endopolygalacturonase 1, respectively. Not only does T. arundinaceum trigger changes in the B. cinerea 98 transcriptome, but the interaction with this pathogen significantly represses the production of HA by T. arundinaceum, indicating that a bidirectional transcriptional regulation is established between these two antagonistic fungi. Finally, the involvement of aspinolides produced by Ta'Tri5 in plant sensitization, by a mechanism independent of HA has been also investigated.

Last Modified: 9/22/2014
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