Drought-induced SlCLE10 coordinates ethylene biosynthesis and root hair development to enhance osmotic stress tolerance in tomato

CLAVATA3/EMBRYO SURROUNDING REGION-related (CLE) peptides are key regulators of cell division in root, shoot, and vascular meristems. However, the role of CLE peptides in regulating root hair growth remains poorly understood. Here, we report that hyperosmotic stress rapidly induces the expression of SlCLE10 in tomato. Overexpression of SlCLE10 increased root hair length and enhanced drought tolerance, whereas the slcle10 knockout mutant exhibited shorter root hairs than the wild type. We further demonstrated that SlCLE10-mediated root hair promotion under osmotic stress depends on ethylene biosynthesis and signaling. Specifically, SlCLE10 enhances the activation of SlMAPK6 and promotes its interaction with SlACS2. SlMAPK6 subsequently phosphorylates SlACS2, stabilizing the protein and increasing ethylene production. These findings define a SlCLE10-SlMAPK6-SlACS2 signaling module that regulates root hair formation under hyperosmotic stress. Notably, exogenous application of SlCLE10 peptide promoted root hair growth in a variety of dicot species, including pepper, eggplant, cucumber, oilseed rape, leafy greens, and tobacco. Our study thus establishes a molecular framework linking environmental stress to CLE peptide-mediated root hair development and proposes a potential strategy for improving crop drought resistance through genetic enhancement of root hair growth.