Trichoderma biocontrol strains establish a complex network of interactions with plants, in which diverse fungal molecules are involved in the recognition of these fungi as nonpathogenic organisms. These molecules act as microbial-associated molecular patts that trigger plant responses. Previous studies have reported the im-portance of ergosterol produced by Trichoderma spp. for the ability of these fungi to induce plant growth and de-fenses. In addition, squalene, a sterol biosynthetic inter-mediate, seems to play an important role in these inter-actions. Here, we analyzed the effect of different concentrations of ergosterol and squalene on tomato (Solanum lycopersicum) growth and on the transcription level of defense- and growth-related genes. We used an RNA-seq strategy to identify several tomato genesencoding predicted patt recognition receptor proteins or WRKY transcription factors, both of which are puta-tively involved in the perception and response to ergo-sterol and squalene. Finally, an analysis of Arabidopsis thaliana mutants lacking the genes homologous to these tomato candidates led to the identification of a WRKY40 transcription factor that negatively regulates salicylic acid-related genes and positively regulates ethylene- and jasmonate-related genes in the presence of ergosterol and squalene.