Phosphatidic acid–driven plasma membrane localization and activation of FER confer salt tolerance in <i>Arabidopsis</i>

Cell wall remodeling and adaptive responses are critical for plant salt tolerance. FERONIA (FER), a key cell wall sensor localized and activated at the plasma membrane, is central to this process. However, the molecular mechanisms governing its plasma membrane localization and activation remain elusive. Here, we found that phospholipase D α1 (PLDα1) and PLDδ physically interact with FER and that PLD-derived phosphatidic acid (PA) stabilizes FER at the plasma membrane and enhances its kinase activity. This PA-driven activation of FER promotes the phosphorylation of COMPANION OF CELLULOSE SYNTHASE1 (CC1), which in turn facilitates CC1 recycling and microtubule reassembly under salt stress. Genetic analyses uncover synergistic functions of PLD α 1 / PLD δ, FER , and CCs in regulating plant salt tolerance. Collectively, our findings reveal that PLDs and FER cooperatively govern microtubule organization under salt stress, unveiling a critical cross-talk between lipid signaling and cell wall signaling in response to stress conditions.