Abstract

BackgroundMembers of the fungal genus Trichoderma directly antagonize soil-borne fungal pathogens, and an increasing number of species are studied for their potential in biocontrol of plant pathogens in agriculture. Some species also colonize plant roots, promoting systemic resistance. The Trichoderma-root interaction is hosted by a wide range of plant species, including monocots and dicots.ResultsTo test the hypothesis that gene expression by the fungal partner in this beneficial interaction is modulated by the plant, Trichoderma virens was co-cultured with maize or tomato in a hydroponic system allowing interaction with the roots. The transcriptomes for T. virens alone were compared with fungus-inoculated tomato or maize roots by hybridization on microarrays of 11645 unique oligonucleotides designed from the predicted protein-coding gene models. Transcript levels of 210 genes were modulated by interaction with roots. Almost all were up-regulated. Glycoside hydrolases and transporters were highly represented among transcripts induced by co-culture with roots. Of the genes up-regulated on either or both host plants, 35 differed significantly in their expression levels between maize and tomato. Ten of these were expressed higher in the fungus in co-culture with tomato roots than with maize. Average transcript levels for these genes ranged from 1.9 fold higher on tomato than on maize to 60.9 fold for the most tomato-specific gene. The other 25 host-specific transcripts were expressed more strongly in co-culture with maize than with tomato. Average transcript levels for these genes were 2.5 to 196 fold higher on maize than on tomato.ConclusionsBased on the relevant role of Trichoderma virens as a biological control agent this study provides a better knowledge of its crosstalk with plants in a host-specific manner. The differentially expressed genes encode proteins belonging to several functional classes including enzymes, transporters and small secreted proteins. Among them, glycoside hydrolases and transporters are highlighted by their abundance and suggest an important factor in the metabolism of host cell walls during colonization of the outer root layers. Host-specific gene expression may contribute to the ability of T. virens to colonize the roots of a wide range of plant species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-014-1208-3) contains supplementary material, which is available to authorized users.

Highlights

  • Members of the fungal genus Trichoderma directly antagonize soil-borne fungal pathogens, and an increasing number of species are studied for their potential in biocontrol of plant pathogens in agriculture

  • The data sets were analyzed in pairs using CyberT for significant differences in transcript abundance: M + Tv compared to Tv, T + Tv compared to Tv, and M + Tv compared to T + Tv

  • The significantly regulated genes cluster according to experiment (Figure 2A), but some genes deviate from the pattern in some experiments

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Summary

Introduction

Members of the fungal genus Trichoderma directly antagonize soil-borne fungal pathogens, and an increasing number of species are studied for their potential in biocontrol of plant pathogens in agriculture. Some species colonize plant roots, promoting systemic resistance. Some members of the genus Trichoderma, including T. virens, T. harzianum, T. asperellum and T. atroviride, are employed as biocontrol agents of plant pathogens worldwide. These soil fungi are keen mycoparasites, generally rhizosphere competent, and some have the ability. The combination of close interaction with plants and the ability to tolerate heavy metals make some strains of T. harzianum [31] and T. virens [32] effective agents for soil bioremediation and plant growth promotion. In hydroponic cultures during early colonization (10 hours), hyphae were observed growing between plant cell walls, and by 24 h, the root surface was extensively colonized. After longer times of interaction in soil (72 hours) the fungus produced yeast-like cells [35]

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