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bioRxiv · 10.1101/2022.11.03.515049

Glutathione activates PHT1;5 gene via WRKY75 transcription factor to regulate phosphate homeostasis in Arabidopsis

Shee, R.·Shee, D.·Sahid, S.·Paul, S.·Datta, R.
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Abstract

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 AtWRKY75. 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 AtWRKY75 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, AtWRKY75 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 statementGlutathione-S-nitrosoglutathione module regulates phosphate translocation in Arabidopsis under phosphate starvation via transcriptional activation of AtPHT1;5 gene by AtWRKY75 transcription factor.

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Shee, R., Shee, D., Sahid, S., Paul, S., Datta, R.. 2022-11-04. Glutathione activates PHT1;5 gene via WRKY75 transcription factor to regulate phosphate homeostasis in Arabidopsis. https://doi.org/10.1101/2022.11.03.515049

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