ABCG Transporter Gene PstABCG2 Contributes to Multidrug Resistance in Puccinia striiformis

The emergence of triadimefon resistance in Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust, threatens global food security. Although the novel SDHI fungicide flubeneteram shows high efficacy, the molecular basis of resistance remains unclear. Here, we identify the ABC transporter gene PstABCG2 as a key multidrug resistance (MDR) determinant in Pst. Transcriptomics revealed its sustained upregulation under fungicide stress. Silencing PstABCG2 via RNAi and HIGS enhanced fungal sensitivity to both fungicides, while heterologous expression in Fusarium graminearum restored resistance. Structural and biophysical analyses identified E1184 as a critical binding residue-its mutation (E1184Y) impaired triadimefon affinity but preserved flubeneteram binding via adaptive halogen bonding. Furthermore, the GATA-family transcription factor PstGATA directly activated PstABCG2 expression, and its silencing phenocopied the hypersensitivity of PstABCG2-silenced isolates. The results provide a theoretical foundation for elucidating multidrug resistance mechanisms in Pst, field resistance management, and novel fungicide target development.