Dissection of CrRLK1L signalling pathways regulating disease susceptibility and resistance to powdery mildew

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CATHARANTHUS ROSEUS RECEPTOR-LIKE KINASE 1-LIKE (CrRLK1L) proteins are important receptors controlling diverse physiological responses. Together with its endogenous RAPID ALKALINISATION FACTOR (RALF) peptide ligands, the CrRLK1L FERONIA (FER) plays central roles during plant growth, development and immunity. FER is a positive regulator of pattern-triggered immunity (PTI) and antibacterial resistance by facilitating the formation of ligand-induced microbe-associated molecular pattern (MAMP) recognition complexes in a RALF peptide-dependent manner. By contrast, FER functions as a susceptibility factor during powdery mildew infection and the underlying mechanism for FER`s role during diverse plant microbe interactions remains unknown. We show that other known FER signalling components modulate plant powdery mildew accommodation, suggesting that RALF-FER represents a pathway hijacked by adapted powdery mildew fungi. Here, we will analyse the mechanistic basis of FER during powdery mildew susceptibility and dissect signalling pathways distinguishing its functional diversity during antibacterial resistance. THESEUS1 (THE1) is a CrRLK1L related to FER but plays a positive role in basal resistance to powdery mildew, suggesting that the repertoire of CrRLK1Ls determine positive and negative infection outcomes. We will explore the functional diversity of Arabidopsis CrRLK1Ls to elucidate the molecular mechanisms that result in disease susceptibility or resistance. FER and related CrRLK1Ls are conserved among all land plants with likely similar functions across species. Barley has six close FER homologs, suggesting that the protein diversified and raising the hypothesis that individual barley homologs take over specific roles of the multifunctional Arabidopsis protein during distinct plant microbe interactions. We want to explore the functional diversity of FER in barley to generate transferable knowledge for future crop improvement strategies.