Root Colonization by Trichoderma atroviride Triggers Induced Systemic Resistance Primarily Independent of the Chitin-mediated Signaling Pathway in Arabidopsis

Chitin/cellulose nanofiber complex from spent mushroom substrate systemically induces plant disease resistance through its cellulose-derived function

Spent mushroom substrate (SMS) is a major agricultural waste generated as a by-product of industrial mushroom cultivation. To valorize SMS, we developed a method to convert it to a form of nanofiber dispersion, chitin/cellulose nanofiber complex (CCNFC), via nanofibrillation. CCNFC application induces plant disease resistance, local immune response, and systemic disease resistance. Because chitin nanofibers (NF) also induce these defense responses, their function has been proposed to contribute to CCNFC-induced disease resistance. Here, we aimed to determine the precise mode of action of CCNFC in inducing plant disease resistance. The local immune response and systemic disease resistance induced by CCNFC were not compromised in Arabidopsis and rice mutants for lysin motif-type pattern recognition receptors involved in chitin perception. Transcriptome analysis revealed similar systemic transcriptional responses in CCNFC- and cellulose NF-treated Arabidopsis plants. Cellulose NF-induced systemic disease resistance but not local immune response. Thus, the local immune response triggered by CCNFC also requires another component(s) in CCNFC other than cellulose, accompanied by chitin. In contrast, the systemic disease resistance induced by CCNFC could be caused mainly by cellulose NF.