β-1,4-d-Glucan-Based Oligomers Modulate PTI to Fine-Tune Lettuce Immune Responses

Area of Science:

• Plant immunity
• Molecular biology
• Crop protection

Background:

• Plant cell wall damage releases damage-associated molecular patterns (DAMPs) that trigger plant immunity.
• The role of cello-oligosaccharides, derived from cellulose, in activating plant immunity is not well understood.

Purpose of the Study:

• To investigate the role of cello-oligosaccharides in activating plant immunity.
• To determine the effect of cello-oligosaccharide chain length on immune responses.
• To explore the potential of cello-oligosaccharides in crop protection.

Main Methods:

• Treatment of *Lactuca sativa* with cello-oligosaccharides of varying chain lengths (DP2-DP5).
• Measurement of immune responses including ROS production, MPK6 phosphorylation, defense gene expression, stomatal closure, and callose/lignin deposition.
• Transcriptomic analysis to understand signaling pathways.
• Assessing the impact of cellotetraose (CEL4) on flg22-induced immunity and *Botrytis cinerea* infection.
• Monitoring plant recovery and growth compatibility.

Main Results:

• Cello-oligosaccharides elicit pattern-triggered immunity (PTI) in a chain-length-dependent manner.
• Cellotetraose (CEL4) induced the strongest immune responses, including ROS burst, MPK6 phosphorylation, defense gene activation, stomatal closure, and callose/lignin deposition.
• Transcriptomic data indicated that chain length qualitatively shapes the immune signaling output.
• CEL4 enhanced flg22-induced immunity and reduced *Botrytis cinerea* infection, demonstrating DAMP-PAMP synergy.
• CEL4-induced immunity was transient and growth-compatible, with full recovery within 12 hours.

Conclusions:

• Chain length is a critical informational cue for carbohydrate DAMPs.
• Cellotetraose (CEL4) acts as a structure-specific, growth-compatible immunomodulator.
• These findings have implications for developing sustainable, immune-centered crop protection strategies.