Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/26/2012
Publication Date: 7/1/2012
Citation: Malmierca, M.G., Cardoza, R.E., Alexander, N.J., McCormick, S.P., Hermosa, R., Monte, E., Gutierrez, S. 2012. Involvement of Trichoderma trichothecenes in the biocontrol activity and in the induction of plant defense related genes. Applied and Environmental Microbiology. 78(14):4856-4868. Interpretive Summary: In this research, we found that a trichothecene is an important factor in the ability of Trichoderma arundinaceum to control plant pathogens. Trichothecenes are toxins that are harmful to the health of humans and livestock because of their ability to block protein synthesis. These toxins are produced by some fungi that infect crop plants and can contaminate food and feed prepared from infected grain. Some strains of Trichoderma, a fungus used for biocontrol of plant pathogens, produce trichothecenes as well as antifungal enzymes. In this study we knocked out a T. arundinaceum toxin gene and found that mutants that cannot make the trichothecene harzianum A (HA) have less antifungal activity. In addition we found that HA was not toxic to tomato plants and that pretreating the plants with HA-producing Trichoderma activated the plant defense response against fungal pathogens. Trichothecene producing strains of T. arundinaceum are good candidates for biocontrol of fungal diseases.
Technical Abstract: Trichoderma species produce trichothecenes, most notably trichodermin and harzianum A (HA), by a biosynthetic pathway in which several of the involved proteins have significant differences in functionality, compared to their Fusarium orthologues. In addition, the genes encoding these proteins show a genomic organization differing from that of the Fusarium tri clusters. Here we describe the isolation of T. arundinaceum IBT 40837 transformants which have a disrupted or silenced tri4, a gene encoding a cytochrome P450 monooxygenase that oxygenates trichodiene to give rise to isotrichodiol, and the effect of the tri4 gene disruption and silencing on the expression of other tri genes. Our results indicate that the tri4 gene disruption resulted in a reduced antifungal activity against Botrytis cinerea and Rhizoctonia solani and also in a reduced ability to induce expression of tomato plant defense-related genes belonging to the salicylic acid (SA) and jasmonate (JA) pathways against B. cinerea, in comparison to the wild type strain, indicating that HA plays an important function in the sensitization of Trichoderma pretreated-plants against this fungal pathogen. Additionally, the effect of the interaction of T. arundinaceum with B. cinerea or with tomato seedlings on the expression of the tri genes was studied.