The Auxin Response Factor TaARF18-A Negatively Regulates Salt Tolerance in Common Wheat (Triticum aestivum L.)

Soil salinization is one of the major abiotic stresses that influences agricultural production and the environment. Auxin response factors (ARFs) are key components of the auxin signal transduction pathway, while their role in wheat salt stress responses remains unclear. In this study, we identified TaARF18 as a negative regulator of salt tolerance in wheat. The coding sequences of TaARF18-A, TaARF18-B, and TaARF18-D were 2106, 2088, and 2088 bp, respectively. TaARF18 is a hydrophilic protein featuring typical Auxin-resp and B3 DNA-binding domains and exhibits relatively high evolutionary conservation among Poaceae species. The expression of TaARF18 was upregulated under salt stress. TaARF18 predominantly accumulated in the nucleus. Silencing of TaARF18 via the BSMV-VIGS approach enhanced salt tolerance in wheat seedlings. In addition, haplotype analysis based on resequencing data from 355 wheat accessions identified 25, 31, and 16 haplotypes for TaARF18-A, TaARF18-B, and TaARF18-D, respectively. Fourteen wheat accessions carrying different haplotypes were evaluated under salt stress, and HapIII of TaARF18-A exhibited the highest level of salt tolerance, which can act as a strong selection locus in global wheat breeding. Our findings provide insight into the function of ARFs in salt stress responses and offer a potential target for CRISPR/Cas-mediated salt-tolerant wheat breeding programs.