Abstract text: The plant cell wall provides structural support while simultaneously constraining cell expansion, requiring dynamic sensing and remodeling during growth. In the moss Physcomitrium patens, we previously showed that two cysteine-rich peptides, Rapid Alkalinisation Factors (RALFs), PpRALF1 and PpRALF2, function redundantly to promote protonemal tip growth. Both peptides bind demethylated polygalacturonic acid (PGA), suggesting that RALFs may act as cell wall integrity sensors. To identify their receptors and downstream signaling components, we performed quantitative phosphoproteomics using non-leaky inducible PpRALF2 overexpression lines. This analysis revealed a membrane-localized Proline-rich Extensin-like Receptor-like Kinase, PERKL1, as a candidate signaling component. We show that PpRALF1 physically interacts with PERKL1 in the apoplast, supporting a receptor–ligand relationship. The P. patens genome encodes five PERKL proteins, and quintuple perkl mutants exhibit severe defects in protonemal tip growth and reduced colony size, phenocopying ralf knockout mutants. Conversely, PERKL1 overexpression induces protonemal cell death, partially suppressed by a phosphomimic PERKL1 variant, suggesting a role in cell wall integrity signaling. PERKL1 accumulates at convex plasma membrane domains adjacent to ablated cells, and phosphoproteomics further identified trafficking-related downstream effectors.Together, our results suggest that PpRALF1–PERKL1 signaling coordinates cell wall integrity sensing with vesicle trafficking to regulate polarized tip growth.