Cellobiose elicits immunity in lettuce conferring resistance to Botrytis cinerea.

This article investigates the role of cellobiose, a cellulose hydrolysis product, as an elicitor of innate immunity in lettuce (Lactuca sativa) against the fungal pathogen Botrytis cinerea. The study demonstrates that exogenous application of cellobiose at moderate concentrations (notably 40 mg l–1) enhances lettuce resistance by activating defense-related enzymes such as β-1,3-glucanase and antioxidative enzymes, and by inducing transcriptional reprogramming involving key immune regulators including ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), PATHOGENESIS-RELATED TRANSCRIPTIONAL ACTIVATOR GENES (PTI6), and WRKY transcription factors. Transcriptome analysis revealed up-regulation of genes associated with plant–pathogen interactions, hormone signaling (notably salicylic acid and ethylene pathways), and receptor-like kinases, suggesting that cellobiose acts as a damage-associated molecular pattern (DAMP) triggering pattern-triggered immunity without inhibiting plant growth. The findings propose a model wherein cellobiose is recognized by yet unidentified plasma membrane receptors, leading to activation of downstream signaling cascades and enhanced disease resistance, highlighting its potential as a plant immune inducer.