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

Phosphorus is a macronutrient that regulates a wide range of physiological processes, including plant growth and development. The scarcity of bioavailable phosphate is often a constraint for plant growth in most agricultural ecosystems. Under phosphate limited conditions, plants increase phosphate acquisition or alter its distribution within tissues by activating different phosphate transporters and phosphate starvation-induced genes. Glutathione (GSH), on the other hand, is known to play a critical role in regulating iron and zinc homeostasis in Arabidopsis. However, how it regulates phosphate homeostasis under phosphate limited conditions remains unexplored. We found that the two GSH-deficient mutants, cad2-1, and pad2-1, were hypersensitive to phosphate starvation. Under phosphate-sufficient condition, the root phosphate content was lower in the mutants but significantly higher in the shoot over the Col-0 plants. The pattern was reversed under phosphate-deficient condition. Interestingly, among the different phosphate transporters analyzed, the AtPHT1;5 was significantly down-regulated in the two GSH-deficient mutants. Treatment with exogenous GSH could alter phosphate accumulation in Col-0 and the pht1;5 complementation lines but not in the pht1;5 mutant. This observation confirmed the role of GSH in phosphate reallocation during phosphate starvation via the AtPHT1;5 transporter. Further, promoter analysis demonstrated that GSH regulates the transcription of the AtPHT1;5 gene. The phosphate-responsive transcription factor (TF), AtWRKY75 was identified to interact with the AtPHT1;5 promoter, and phosphate deficiency or GSH treatment enhanced its binding affinity. Together our investigation delineates that GSH regulates the AtPHT1;5 transporter via the AtWRKY75 TF to modulate phosphate distribution under altered phosphate conditions. Summary statementGlutathione regulates phosphate translocation in Arabidopsis under altered phosphate condition via transcriptional activation of AtPHT1;5 gene by AtWRKY75 transcription factor.