Cell wall influences immune response to the elicitor surfactin in Arabidopsis thaliana

Induced systemic resistance triggered by beneficial bacteria is a promising solution to reduce the use of chemical pesticides in agriculture. These bacteria stimulate plant immunity through the production of small secondary metabolites, reducing the incidence of pathogen infection.
The lipopeptide surfactin (SRF) produced by plant beneficial bacilli is one of these metabolites stimulating plant immunity. Our previous research on plants and biomimetic models have demonstrated that this molecule is sensing by plant cells through its interaction with the lipid fraction of the plasma membrane (PM) rather than through protein pattern recognition receptors. We assumed that SRF disturbs physical and organisational properties of PM and consequently activates PM proteins sensitive to membrane mechanics, triggering signalling leading ultimately to plant defence elicitation.
Nevertheless, the PM is tightly connected to the cell wall (CW) which has an important influence on its organisation, possibly influencing cell responses through external stimuli. To investigate a potential influence of CW in the perception of SRF, experiments were performed on freshly isolated protoplasts without CW and on older protoplasts with a recovered CW.
Our preliminary results showed that the presence of CW modifies the cell response to SRF with a reduction of the cytosolic calcium influx and the membrane rigidification. The ROS production seems also impacted with a slightly higher increase in older protoplasts and a change in the shape of the response curve in the first minutes.
To better understand the mechanism by which the CW influences the perception of SRF, further experiments with targeted modification of CW component are ongoing.