Regulation of pathogen defence by plant cell wall integrity signalling

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Cell walls are of fundamental importance for the growth, development and stress resistance of plants. The functional requirements of the cell wall structure differ depending on the current developmental and environmental situation. Cell wall integrity (CWI) is monitored by plasma membrane-localised proteins that, when integrity is compromised, induce downstream responses to allow cell wall adaptation. These responses are coordinated with cellular metabolism and signalling networks, for example during pathogen infection. Previous work has shown that CWI signalling in Arabidopsis thaliana is regulated by plant elicitor peptides (PEPs), which may mediate a crosstalk between CWI and defence signalling pathways. In the first part of this project, we will (i) identify molecular components required for PEP detection upon cell wall damage and (ii) investigate the role of stress-dependent changes in localisation and processing of PEP propeptides. In the second part of the project, we will investigate the activation and regulation of defence responses upon CWI impairment. Preliminary evidence indicates that the accumulation of phytoalexins is triggered by cell wall damage and regulated by PEPs. To further elucidate the crosstalk between CWI and PEP signalling pathways and characterise its impact on pathogen defence, we will (i) investigate the contributions of the receptor kinase THESEUS1 and the elicitor peptide PEP3 in this process, (ii) identify genes required for crosstalk between CWI and PEP signalling pathways, and (iii) analyse the efficacy of CWI-dependent defence responses against the cell wall-penetrating phytopathogenic fungus Colletotrichum higginsianum.This project will use genetic, cell biological and physiological methods to gain new insights into the coordination of abiotic/cell wall and biotic stress signalling and determine the impact of these signalling pathways on the outcome of pathogen infections.