Trichoderma and plants on chat.

In a natural environment plant roots and soil microbes are in constant association. The result is a fine interplay based on signals and chemical messages continuously shared by the players. Filamentous microbes reveal their presence to plants by releasing molecules referred to as Microbe Associated Molecular Patterns (MAMPs). Among those, Trichoderma spp. are common components of the soil and rhizosphere microbiome, and they can strongly influence plant growth, development and resistance to biotic and abiotic stresses. It is well established that plants modulate their metabolism in response to Trichoderma and in turn Trichoderma may respond by changing its own behaviour. Our studies are aimed at understanding which are the players involved in the multifaceted chatting between Trichoderma and the plant. Here we present the results of a wholetranscriptome study of the interplay between tomato roots and the beneficial strain T. harzianum T22. In this study, we detected large transcriptomic perturbations in both T. harzianum-treated tomato roots and in Trichoderma mycelia interacting with tomato. Moreover, we have verified that root colonization by a selected Trichoderma beneficial strain modifies the outcome of the complex, multiplayer interaction among plants, aphids and their natural enemies, by modulating Volatile Organic Compounds (pVOCs) composition. We have also studied and further characterized one of the Trichoderma MAMPs, the HYTLO1 hydrophobin, demonstrating that when exogenously added to a Lotus japonicus cell culture, it can trigger a signal transduction pathway leading to the activation of defense genes in a Ca2+-dependent manner. Moreover, we showed that perception of HYTLO1 by the plant occurs at the cell surface, and that the fungal secreted hydrophobin is selectively located in the apoplastic space, where it forms a web-like network with patches close to the plasma membrane.