Mechano-transduction via the pectin-FERONIA complex regulates ROP6 GTPase signaling in Arabidopsis

During growth and morphogenesis, plant cells respond to mechanical stresses resulting from spatiotemporal changes in the cell wall that bear high internal turgor pressure. Microtubule (MT) arrays are re-organized to align in the direction of maximal tensile stress to guide the synthesis of cellulose, reinforcing the local cell wall. However, how mechanical forces regulate MT re-organization remains largely unknown. Here, we demonstrate that mechanical signaling that is based on the CrRLK1L subfamily receptor kinase FERONIA (FER) regulates the reorganization of cortical MT in cotyledon epidermal pavement cells (PC) in Arabidopsis. Recessive mutations in FER compromised MT response to mechanical perturbations such as single cell ablation, compression and Isoxaben treatment in these pavement cells. These perturbations promoted the activation of ROP6 GTPase that acts directly downstream of FER. Furthermore, defects in the ROP6 signaling pathway negated the reorganization of cortical MTs induced by these stresses. Finally, reduction in highly demethylesterified pectin, which binds the extracellular malectin domain of FER and is required for FER-mediated ROP6 activation, also impacted mechanical induction of cortical MT reorganization. Taken together our results suggest that the FER-pectin complex senses and/or transduce mechanical forces to regulate MT organization through activating the ROP6 signaling pathway in Arabidopsis.