A small peptide enhances cotton salt tolerance via MPK3/6 activation: Functional discovery of GhPIPL7 in salt stress signaling

Cotton ( Gossypium spp.) production is increasingly threatened by soil salinization, yet the roles of endogenous peptide regulators in salt stress responses remain largely unexplored. INFLORESCENCE DEFICIENT IN ABSCISSION (IDA)/IDA-Like (IDL) and PAMP-INDUCED SECRETED PEPTIDE (PIP)/PIP-Like (PIPL) peptides have been implicated in plant development and stress adaptation, but their specific functions in cotton are unclear. We hypothesized that certain IDA/IDL and PIP/PIPL peptides enhance salt tolerance by modulating stress-responsive signaling pathways. To test this, we identified 63 IDA / IDL and 29 PIP / PIPL genes across four Gossypium species and analyzed their gene structures, chromosomal distribution, promoter elements, and expression profiles under abiotic stress. In G. hirsutum , GhIDL02 and GhPIPL7 showed strong induction by salt stress. Functional validation via virus-induced gene silencing (VIGS) and exogenous peptide application revealed that both peptides enhance salt tolerance by improving Na⁺/K⁺ homeostasis. Transcriptomic and molecular analyses further demonstrated that GhPIPL7 confers salt tolerance by activating mitogen-activated protein kinases 3 and 6 (MPK3/6) signaling. These findings uncover a peptide-mediated regulatory mechanism of salt stress and identify GhPIPL7 as a promising candidate for molecular breeding, highlighting the potential of endogenous small peptides as targets for improving salt resilience in cotton. • GhPIPL7 enhances salt tolerance by activating MPK3/6 signaling, revealing a peptide-mediated stress pathway. • Silencing and peptide treatments show that GhPIPL7 and GhIDL02 positively regulate salt and drought tolerance. • GhPIPL7 improves Na⁺/K⁺ balance under salt stressbased on ionassays. • Transcriptome and phospho-MAPK analyses confirm that GhPIPL7 activates MAPK and hormone pathways under salt stress. • This is the first genome-wide study of IDL and PIPL peptides in Gossypium species.