OsFH14 Regulates Salt-Induced Plasmodesmata Permeability Enhancement to Promote Rice Salt Tolerance Through Actin Bundling.

Plasmodesmata (PD)-mediated intercellular communication is critical for plant stress adaptation, yet its dynamic regulation by the actin cytoskeleton under abiotic stress remains poorly characterised. Here, we show that rice OsFH14 modulates salt-induced PD permeability to enhance salt tolerance. Through CRISPR-Cas9 mutagenesis and subcellular localisation analyses, we first demonstrate that OsFH14 specifically localises to PD and is strictly required for salt stress-induced increases in PD permeability. Osfh14 mutants exhibit reduced PD permeability and enhanced sensitivity to NaCl treatment. Mechanistic investigations show that OsFH14 functions as a specialised actin-bundling protein that stabilises existing actin filaments without nucleation or capping activity, which suggests that OsFH14 probably regulates salt tolerance by maintaining PD-associated actin cytoskeletal integrity. Supporting this hypothesis, pharmacological disruption of actin dynamics using Latrunculin B (LatB) phenocopies Osfh14 mutant defects, specifically impairing both PD permeability regulation and salt tolerance. Conversely, pretreatment of Osfh14 mutants with the actin filament stabiliser Jasplakinolide (Jasp) recovers PD permeability after salt treatment and they exhibit salt tolerance phenotypes indistinguishable from wild-type (WT) plants. These findings establish a causal link between OsFH14-mediated actin bundling at PD and salt tolerance, highlighting PD-associated actin dynamics as a key adaptive strategy for crop salt tolerance.