Abstract

The phytohormone auxin orchestrates root development through intricate signaling networks. In the non-canonical auxin pathway, both the transmembrane kinase (TMK)-mediated signaling and the mitogen-activated protein kinase (MAPK) cascade are shown to be involved in the auxin-regulated lateral root (LR) formation. However, the role and mechanism of the receptor-like kinase FERONIA (FER) in this process remain unclear. Here, quantitative proteomic and phosphoproteomic analyses of Arabidopsis roots identify FER, MPK3/6, and WRKY3/4 as auxin-responsive components. Further analyses reveal that FER functions as a negative regulator of LR development by modulating cell division patterns within LR primordia. FER interacts with and phosphorylates MPK3/6, which then phosphorylate the transcription factors WRKY3 and WRKY4 to form a repressive module that ultimately suppresses LR organogenesis. Collectively, our findings define a FER–MPK3/6–WRKY3/4 signaling module that negatively regulates LR formation, demonstrating a previously unknown integration of FER-mediated signaling into the MAPK cascade in auxin-triggered organogenesis.