Our previous study indicated that glycerol application induced resistance to powdery mildew (Bgt) in wheat by regulating two important signal molecules, glycerol-3-phosphate (G3P) and oleic acid (OA18:1). Transcriptome analysis of wheat leaves treated by glycerol and inoculated with Bgt was performed to identify the activated immune response pathways. We identified a set of differentially expressed transcripts (e.g., TaGLI1, TaACT1, and TaSSI2) involved in glycerol and fatty acid metabolism that were upregulated in response to Bgt infection and might contribute to G3P and OA18:1 accumulation. Gene Ontology (GO) enrichment analysis revealed GO terms induced by glycerol, such as response to jasmonic acid (JA), defense response to bacterium, lipid oxidation, and growth. In addition, glycerol application induced genes (e.g., LOX, AOS, and OPRs) involved in the metabolism pathway of linolenic and alpha-linolenic acid, which are precursor molecules of JA biosynthesis. Glycerol induced JA and salicylic acid (SA) levels, while glycerol reduced the auxin (IAA) level in wheat. Glycerol treatment also induced pathogenesis related (PR) genes, including PR-1, PR-3, PR-10, callose synthase, PRMS, RPM1, peroxidase, HSP70, HSP90, etc. These results indicate that glycerol treatment regulates fatty acid metabolism and hormones cross-talk and induces the expression of PR genes that together contribute to Bgt resistance in wheat.

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.