Abstract

The Casparian strip (CS) and suberin form the apoplastic barrier, which blocks solute entry into the vascular stele under high-salt conditions. Here, transcriptome analysis of Arabidopsis roots during three stages of apoplastic barrier development (undifferentiated, differentiating, and mature) revealed differential expression of the transcription factor gene WRKY71 . We generated WRKY71 -overexpression (OE) and WRKY71- complementation (COM) lines. Metabolomics analysis showed that WRKY71 promotes the biosynthesis of S-type lignin monomers. Compared to wild type and wrky71 plants, WRKY71- OE and COM plants showed enhanced apoplastic barrier formation and less Na + accumulation under 100 mM NaCl treatment, exhibiting better salt-exclusion ability during germination and seedling growth. Yeast one-hybrid assays revealed that WRKY71 interacts with the lignin biosynthesis genes 4CL3 and CUTICLE DESTRUCTING FACTOR 1 ( CDEF1 ). WRKY71 promotes 4CL3 expression and inhibits CDEF1 expression, as determined by dual-luciferase reporter assay. To further investigate the functions of 4CL3 and CDEF1 , we generated the corresponding OE lines. Under 100 mM NaCl treatment, 4CL3 -OE plants showed enhanced salt tolerance through increased CS formation, whereas CDEF1 -OE plants showed increased salt sensitivity due to inhibited suberin formation. Our identification of the WRKY71– 4CL3 / CDEF1 module sheds light on the role of the apoplastic barrier in salt tolerance.