A Cystine Transporter Mediates Nutrient Acquisition and Redox Balance During Wheat Stripe Rust Infection

Amino acid uptake is crucial for the pathogenicity of Puccinia striiformis f. sp. tritici (Pst), the causative agent of wheat stripe rust. In this study, we investigated the dynamics of cystine accumulation in wheat leaves during Pst infection and identified Pst cystine transporters involved in this process. Amino acid profiling revealed a marked increase in cystine content at early infection stages. Phylogenetic analysis and expression profiling identified four candidate Pst cystine transporter genes, among which PstAZ2B02G00053 (designated as PstCYN1) was functionally validated through yeast complementation assays. Subcellular localisation studies confirmed PstCYN1 as a plasma membrane transporter. Silencing of PstCYN1 via BSMV-VIGS and RNAi significantly reduced Pst virulence, as evidenced by decreased fungal biomass, reduced haustorial formation and fewer urediniospore pustules. Furthermore, apoplastic cystine accumulation and reactive oxygen species (ROS) levels were elevated in PstCYN1-silenced plants, indicating that PstCYN1 mediates not only cystine uptake but also redox regulation at the infection interface. These findings highlight the critical role of PstCYN1 in Pst nutrient acquisition and defence suppression, providing potential targets for enhancing wheat resistance against stripe rust.