Glutathione induces ArabidopsisPHT1;5gene via WRKY75 transcription factor to regulate phosphate homeostasis

Phosphorus (P) is essential for plant growth, yet inorganic phosphate (Pi) is often limiting in soil. Plants respond to Pi limitation by activating P transporters and starvation genes, which boost Pi uptake or redistribute P. While glutathione (GSH) regulates iron and zinc homeostasis in Arabidopsis, its role in P homeostasis under Pi limitation remains elusive. Here, we show that GSH-S-nitrosoglutathione (GSNO) module regulates source-to-sink P allocation in Arabidopsis by transcriptionally activating the phloem-localised transporter AtPHT1;5 via the transcription factor At WRKY75. GSH-deficient mutants, cad2-1 and pad2-1 , exhibited sensitivity to Pi-starvation with altered root system architecture, reduced anthocyanin accumulation, and disrupted root–to-shoot P transport. AtPHT1;5 transcript levels were markedly reduced in these mutants but were positively responsive to exogenous GSH or GSNO. The pht1;5 mutant failed to respond to GSH treatments, demonstrating that AtPHT1;5 is essential for GSH-mediated P mobilisation. Pharmacological and genetic manipulation of nitric oxide (NO)/GSNO levels implicated GSNO as an essential intermediary. In depth molecular analyses identified At WRKY75 as a Pi- and GSH/GSNO-responsive activator that binds w-box motifs in the AtPHT1;5 promoter. This was further supported by the lack of AtPHT1;5 induction in the wrky75 mutants. Finally, At WRKY75 is S-nitrosylated and stabilised by GSH/GSNO, providing a mechanistic link between redox/NO signalling and transcriptional control of P transport. We propose that elevated GSH under Pi limitation is converted to GSNO, which S-nitrosylates AtWRKY75 and promotes AtPHT1;5 expression, thus driving source-to-sink P reallocation. This pathway integrates redox and NO signalling with transcriptional regulation to maintain P homeostasis under Pi starvation. Summary statement Glutathione-S-nitrosoglutathione module regulates phosphate translocation in Arabidopsis under phosphate starvation via transcriptional activation of AtPHT1;5 gene by At WRKY75 transcription factor.