Abstract
BackgroundThe proteins Sm1 and Sm2 from the biocontrol fungus Trichoderma virens belong to the cerato-platanin protein family. Members of this family are small, secreted proteins that are abundantly produced by filamentous fungi with all types of life-styles. Some species of the fungal genus Trichoderma are considered as biocontrol fungi because they are mycoparasites and are also able to directly interact with plants, thereby stimulating plant defense responses. It was previously shown that the cerato-platanin protein Sm1 from T. virens - and to a lesser extent its homologue Epl1 from Trichoderma atroviride - induce plant defense responses. The plant protection potential of other members of the cerato-platanin protein family in Trichoderma, however, has not yet been investigated.ResultsIn order to analyze the function of the cerato-platanin protein Sm2, sm1 and sm2 knockout strains were generated and characterized. The effect of the lack of Sm1 and Sm2 in T. virens on inducing systemic resistance in maize seedlings, challenged with the plant pathogen Cochliobolus heterostrophus, was tested. These plant experiments were also performed with T. atroviride epl1 and epl2 knockout strains. In our plant-pathogen system T. virens was a more effective plant protectant than T. atroviride and the results with both Trichoderma species showed concordantly that the level of plant protection was more strongly reduced in plants treated with the sm2/epl2 knockout strains than with sm1/epl1 knockout strains.ConclusionsAlthough the cerato-platanin genes sm1/epl1 are more abundantly expressed than sm2/epl2 during fungal growth, Sm2/Epl2 are, interestingly, more important than Sm1/Epl1 for the promotion of plant protection conferred by Trichoderma in the maize-C. heterostrophus pathosystem.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0333-0) contains supplementary material, which is available to authorized users.
Highlights
The proteins Sm1 and Sm2 from the biocontrol fungus Trichoderma virens belong to the cerato-platanin protein family
In order to assess the transcriptional profiles of all three genes encoding Cerato platanin protein (CPP) in T. virens, their expression was first analyzed with RT-PCR
In biomass harvested from sporulating cultures grown on potato dextrose agar (PDA) plates during different stages of spore maturation, ranging from mycelium covered with white conidia to first light green and dark green conidia, sm2 was found to be strongly upregulated, but sm1 was found to be expressed (Figure 1b)
Summary
The proteins Sm1 and Sm2 from the biocontrol fungus Trichoderma virens belong to the cerato-platanin protein family. Members of this family are small, secreted proteins that are abundantly produced by filamentous fungi with all types of life-styles. It was previously shown that the cerato-platanin protein Sm1 from T. virens - and to a lesser extent its homologue Epl from Trichoderma atroviride - induce plant defense responses. Gaderer et al BMC Microbiology (2015) 15:2 associated) molecular patterns activate systemic resistance The first such secreted protein to be studied in detail in Trichoderma-plant interactions was a small secreted cysteine-rich protein belonging to the cerato-platanin protein (CPP) family, named Sm1/Epl in Trichoderma virens and Trichoderma atroviride, respectively [5,6]. Single and double knockout strains of epl and epl did not reveal any phenotype related to hyphal growth or development
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