Institute of Biology II, Molecular Plant Physiology (MoPP), University of Freiburg, Freiburg, Germany; Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg, Germany
Kai Dünser
Institute of Biology II, Molecular Plant Physiology (MoPP), University of Freiburg, Freiburg, Germany; Institute of Molecular Plant Biology (IMPB), Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria
Chenlu Liu
Institute of Biology II, Molecular Plant Physiology (MoPP), University of Freiburg, Freiburg, Germany; Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg, Germany
Core Facility Signalling Factory & Robotics, University of Freiburg, Freiburg im Breisgau, Germany; Centre for Biological Signalling Studies (BIOSS), University of Freiburg, Freiburg im Breisgau, Germany
Institute of Biology II, Molecular Plant Physiology (MoPP), University of Freiburg, Freiburg, Germany; Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg, Germany
Institute of Biology II, Molecular Plant Physiology (MoPP), University of Freiburg, Freiburg, Germany; Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg, Germany; Institute of Molecular Plant Biology (IMPB), Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria
The extracellular matrix plays an integrative role in cellular responses in plants, but its contribution to the signalling of extracellular ligands largely remains to be explored. Rapid alkalinisation factors (RALFs) are extracellular peptide hormones that play pivotal roles in various physiological processes. Here, we address a crucial connection between the de-methylesterification machinery of the cell wall component pectin and RALF1 activity. Pectin is a polysaccharide, contributing to the structural integrity of the cell wall. Our data illustrate that the pharmacological and genetic interference with pectin methyl esterases (PMEs) abolishes RALF1-induced root growth repression. Our data suggest that positively charged RALF1 peptides bind negatively charged, de-methylesterified pectin with high avidity. We illustrate that the RALF1 association with de-methylesterified pectin is required for its FERONIA-dependent perception, contributing to the control of the extracellular matrix and the regulation of plasma membrane dynamics. Notably, this mode of action is independent of the FER-dependent extracellular matrix sensing mechanism provided by FER interaction with the leucine-rich repeat extensin (LRX) proteins. We propose that the methylation status of pectin acts as a contextualizing signalling scaffold for RALF peptides, linking extracellular matrix dynamics to peptide hormone-mediated responses.
