The miR171a-TaSCL6-1 Module Acts Downstream of miR164-Targeted TaNAC21/22 to Regulate Leaf Rust Resistance in Wheat

Wheat leaf rust, caused by Puccinia triticina, poses a significant threat to global wheat production. MicroRNAs (miRNAs) are critical regulators of plant growth, development and stress responses; however, their role in wheat resistance to leaf rust remains poorly understood. In this study, we identified the miR171a-TaSCL6-1 module as a key regulator of leaf rust resistance in wheat. Expression of miR171a was upregulated in wheat seedlings following pathogen inoculation. Transgenic assays, including overexpression and short tandem target mimic approaches, demonstrated that miR171a negatively regulates resistance to leaf rust. Degradome sequencing confirmed TaSCL6-1 as the primary target of miR171a, and both overexpression and knockout of TaSCL6-1 established its role as a positive regulator of resistance. Transcriptome analysis revealed that TaSCL6-1 upregulates defence-related genes encoding peroxidases and transcription factors. TaSCL6-1 can activate the transcription of downstream genes by binding to the GAA motif in the promoters, and silencing of downstream genes (TaPOD2, TaPOD35 and TaERF114) increased wheat susceptibility to leaf rust. Furthermore, miR164-targeted TaNAC21/22 acts as an upstream regulator of MIR171a by binding to its promoter and activating its expression. Overexpression of TaNAC21/22 increased susceptibility to leaf rust, whereas transient silencing of TaNAC21/22 or overexpression of miR164 enhanced seedling resistance to leaf rust. Our findings elucidate the role of the miR171a-TaSCL6-1 module in regulating wheat defence against leaf rust, providing potential genetic targets for breeding resistant wheat varieties.