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, their roles in the regulation of root hair growth remain poorly understood. Here, we report that SlCLE10 expression is rapidly induced by hyperosmotic stress in tomato. Overexpression of SlCLE10 increases root hair length and enhances drought tolerance, whereas the slcle10 knockout mutant exhibits shorter root hairs than the wild type. We further demonstrate that SlCLE10-mediated promotion of root hair growth under osmotic stress depends on ethylene biosynthesis and signaling. Mechanistically, SlCLE10 enhances the activation of SlMAPK6 and promotes its interaction with SlACS2. Activated SlMAPK6 subsequently phosphorylates SlACS2, thereby stabilizing the protein and increasing ethylene production. These findings define an SlCLE10-SlMAPK6-SlACS2 signaling module that regulates root hair formation under hyperosmotic stress. Notably, exogenous application of the SlCLE10 peptide promotes root hair growth across a range of dicot species, including pepper, eggplant, cucumber, oilseed rape, leafy greens, and tobacco. Collectively, our results establish a molecular framework linking environmental stress to CLE-peptide-mediated root hair development and propose a potential strategy for improving crop drought resistance through genetic enhancement of root hair growth.