The riddles of Trichoderma induced plant immunity

Since the initial finding of Trichoderma as a biocontrol agent, efforts have been largely focused on understanding the role of glycosyl hydrolases and antibiotics in mycoparasitism, plant pathogen suppression and other plant growth promotion attributes. However, comparatively less attention has been given for reviewing the role of Trichoderma-derived molecules in plant immunity. Microbial derived molecular signatures are well known for the induction of systemic resistance in plants. In general, the molecules from non-pathogenic microorganisms, activate the plant's immune response via induced systemic response (ISR) that is driven through jasmonic acid (JA) / ethylene (ET) pathways whereas the signature molecules of pathogens origin, induce systemic acquired resistance (SAR) which is driven by salicylic acid (SA). The role of Trichoderma, in triggering the plant immunity has been studied in isolation both at local and systemic level. In this context, various signature molecules from Trichoderma and their roles in activating the plant immune responses have been identified. The elicitors such as Epl1 from Trichoderma through synergistic action, involving both JA / ET as well as SA primed systemic resistance. Furthermore, histone modification system from endophytic strain of Trichoderma through its epigenetic modification of histone proteins have been explored for modulating the expression of genes. The recent experimental studies have unraveled new players of Trichoderma induced systemic resistance with their probable role in SAR as well ISR mediated response. Here, we have described the complexity of biological repertoire and multifaceted aspects of Trichoderma in mediating the plant immune response.