Cellulose-derived oligomers act as damage-associated molecular patterns and trigger defense-like responses
Authors: de Azevedo Souza C, Li S, Lin AZ, Boutrot F, Grossmann G, Zipfel C, Somerville S
CellNetworks People: Grossmann Guido
Journal: Plant Physiol. 2017 Feb 27. pii: pp.01680.2016. doi: 10.1104/pp.16.01680

The plant cell wall, often the site of initial encounters between plants and their microbial pathogens, is composed of a complex mixture of cellulose, hemicellulose and pectin polysaccharides, as well as proteins. The concept of damage-associated molecular patterns (DAMPs) was proposed to describe plant elicitors like oligogalacturonides (OGs), which can be derived by the breakdown of the pectin homogalacturon by pectinases. OGs act via many of the same signaling steps as pathogen- or microbe-associated molecular patterns (PAMPs) to elicit defenses and provide protection against pathogens. Given both the complexity of the plant cell wall and the fact that many pathogens secrete a wide range of cell wall degrading enzymes, we reasoned that the breakdown products of other cell wall polymers may be similarly biological active as elicitors and may help to reinforce the perception of danger by plant cells. Our results indicate that oligomers derived from cellulose are perceived as signal molecules in Arabidopsis, triggering a signaling cascade that shares some similarities to responses to well-known elicitors such as chito-oligomers and OGs. However, in contrast to other known P/DAMPs, cellobiose stimulates neither detectable ROS production nor callose deposition. Confirming our idea that both PAMPs and DAMPs are likely to co-occur at infection sites, co-treatments of cellobiose with flg22 or chito-oligomers led to synergistic increases in gene expression. Thus, the perception of cellulose-derived oligomers may participate in cell wall integrity surveillance, and represents an additional layer of signaling following plant cell wall breakdown during cell wall remodeling or pathogen attack.