|MALMIERCA, M - University Of Leon|
|CARDOZA, R - University Of Leon|
|MONTE, E - University Of Salamanca|
|ALEXANDER, N - Retired ARS Employee|
|GUTIERREZ, S - University Of Leon|
Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2015
Publication Date: 11/15/2015
Citation: Malmierca, M.G., McCormick, S.P., Cardoza, R.E., Monte, E., Alexander, N.J., Gutierrez, S. 2015. Trichodiene production in a Trichoderma harzianum erg1-silenced strain provides evidence of the importance of the sterol biosynthetic pathway in inducing plant defense-related gene expression. Molecular Plant-Microbe Interactions. 28(11):1181-1197.
Interpretive Summary: The fungus Trichoderma has been used as a biocontrol agent against fungal plant pathogens. In order to study how terpenes mediate the complex interaction between the biocontrol agent, the plant, and the pathogens, we manipulated genes for production of ergosterol, a terpene found in fungal membranes, and trichodiene, a volatile terpene chemical precursor of harzianum A, a trichothecene produced by T. arundinaceum. In this research we found that terpenes produced by Trichoderma affect the expression of both defense genes in the plant and virulence genes in the pathogen. This research provides scientists with tools to identify factors that are important in biocontrol of disease-causing fungi and may aid in designing safe and effective biocontrol organisms to use against plant fungal diseases.
Technical Abstract: Trichoderma species are often used as biocontrol agents against plant-pathogenic fungi. A complex molecular interaction occurs among the biocontrol agent, the antagonistic fungus, and the plant. Terpenes and sterols produced by the biocontrol fungus have been found to affect gene expression in both the antagonistic fungus and the plant. The terpene trichodiene (TD) elicits the expression of genes related to tomato defense and to Botrytis virulence. We show here that TD itself is able to induce the expression of Botrytis genes involved in the synthesis of botrydial (BOT) and also induces terpene gene expression in Trichoderma spp. The terpene ergosterol, in addition to its role as a structural component of the fungal cell membranes, acts as an elicitor of defense response in plants. In the present work, using a transformant of T. harzianum, which is silenced in the erg1 gene and accumulates high levels of squalene, we show that this ergosterol precursor also acts as an important elicitor molecule of tomato defense-related genes and induces Botrytis genes involved in BOT biosynthesis, in both cases, in a concentration-dependent manner. Our data emphasize the importance of a balance of squalene and ergosterol in fungal interactions as well as in the biocontrol activity of Trichoderma spp.