Abstract
BackgroundTrichoderma spp. can establish beneficial interactions with plants by promoting plant growth and defense systems, as well as, antagonizing fungal phytopathogens in mycoparasitic interactions. Such interactions depend on signal exchange between both participants and can be mediated by effector proteins that alter the host cell structure and function, allowing the establishment of the relationship. The main purpose of this work was to identify, using computational methods, candidates of effector proteins from T. virens, T. atroviride and T. reesei, validate the expression of some of the genes during a beneficial interaction and mycoparasitism and to define the biological function for one of them.ResultsWe defined a catalogue of putative effector proteins from T. virens, T. atroviride and T. reesei. We further validated the expression of 16 genes encoding putative effector proteins from T. virens and T. atroviride during the interaction with the plant Arabidopsis thaliana, and with two anastomosis groups of the phytopathogenic fungus Rhizoctonia solani. We found genes which transcript levels are modified in response to the presence of both plant fungi, as well as genes that respond only to either a plant or a fungal host. Further, we show that overexpression of the gene tvhydii1, a Class II hydrophobin family member, enhances the antagonistic activity of T. virens against R. solani AG2. Further, deletion of tvhydii1 results in reduced colonization of plant roots, while its overexpression increases it.ConclusionsOur results show that Trichoderma is able to respond in different ways to the presence of a plant or a fungal host, and it can even distinguish between different strains of fungi of a given species. The putative effector proteins identified here may play roles in preventing perception of the fungus by its hosts, favoring host colonization or protecting it from the host’s defense response. Finally, the novel effector protein TVHYDII1 plays a role in plant root colonization by T, virens, and participates in its antagonistic activity against R. solani.
Highlights
Trichoderma spp. can establish beneficial interactions with plants by promoting plant growth and defense systems, as well as, antagonizing fungal phytopathogens in mycoparasitic interactions
In addition to plant protection by direct attack to pathogens, it has been shown that Trichoderma has the ability to establish beneficial interactions with plants, by promoting plant growth and development, possibly through the production of auxinlike compounds and other secondary metabolites [5,6,7,8,9], and enhancing the plant defense response against pathogens like B. cinerea and Pseudomonas syringae, promoting the accumulation of phytoalexins, salicylic and jasmonic acids [8, 10]
We focused on the identification of possible effector-like proteins among the predicted secretomes of T. atroviride and T. virens and the selection of some of the effector coding genes in order to validate their expression during the interaction with A. thaliana plants and in direct confrontation with the phytopathogen Rhizoctonia solani
Summary
Trichoderma spp. can establish beneficial interactions with plants by promoting plant growth and defense systems, as well as, antagonizing fungal phytopathogens in mycoparasitic interactions Such interactions depend on signal exchange between both participants and can be mediated by effector proteins that alter the host cell structure and function, allowing the establishment of the relationship. Effector-like proteins may play an important role in the establishment of the interaction, as occurs in the mycorhizal symbiosis or in the nitrogen fixing nodules. In these cases, proteins like MiSSP7 from Laccaria bicolor or NOD factors from Rhizobium, alter the physiology of the plant to promote the successful establishment of the biological relationship [11,12,13]
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