Tyrosol as a regulating molecule of the Trichoderma-tomato interaction: basis for the development of biofertilisers and biofungicides

Abstract

Title: Tyrosol as a regulating molecule of the Trichoderma-tomato interaction: basis for the development of biofertilisers and biofungicides Trichoderma is widely used in several crops due to its capacity for suppressing disease and stimulating plant development, and a large number of commercialised biocontrol products have been derived from this genus. Recent studies have shown the capacity of Trichoderma spp. to interact with plant hosts by colonising the root epidermis and acting as a plant symbiont. Root colonisation by Trichoderma produces changes in plant metabolism that can result in root development, as well as increased productivity and stress resistance. For this reason, increasing attention has been given to the interactions between Trichoderma and plants, and molecular studies have examined the bioactive compounds produced by the fungus that are associated with plant defence mechanisms, root colonisation and growth promotion. Genomic and proteomic techniques have helped identify the molecular factors involved in the communication between Trichoderma and plants. These tools have contributed to the understanding of these interactions, but several problems remain, impeding the viable commercialisation of Trichoderma. These issues include increasing the production of certain metabolites by Trichoderma, selecting efficient biocontrol and/or biofertiliser strains and developing propagation methods for this fungus.The present project is based on the hypothesis that tyrosol regulates the phenotypic changes of Trichoderma necessary for its colonisation of plant root epidermis and root cortex intercellular spaces; the compound's role as a virulence factor is discarded, as Trichoderma is not a pathogen and does not enter plant cells. The increased expression of the genes of the tyrosol pathway during interactions with tomato, as well as their decreased expression during interactions with other fungi, supports this hypothesis. (A research group from the University of Salamanca has shown that strains of Trichoderma produce tyrosol).Tyrosol is a signalling molecule, produced by a number of soil fungi, with important roles in several phases of microbial growth. The compound acts on phytopathogens and has other functions in the induction of resistance. The production of tyrosol by multiple endophyte fungi may be related to signalling pathways for the production of other important secondary metabolites.The objectives of the project are as follows: to characterise a gene involved in the synthesis of tyrosol (shikimate pathway) in Trichoderma reesei and Trichoderma harzianum; to analyse how tyrosol production in T. reesei and T. harzianum affects the interactions between fungi and plants; to investigate the importance of tyrosol in the regulation of the circadian rhythm of T. reesei in the colonisation of tomato roots, plant development and the defence of tomato plants against Botrytis; to evaluate the effects of tyrosol-defective mutants of T. reesei on the circadian clock and light perception of tomato plants; to show the plant growth-promoting effects of T. reesei and understand the mechanisms of its interactions with plants; and to develop a T. reesei-based product for use as a biofertiliser. (AU)