Role of sulfur in combating arsenic stress through upregulation of important proteins, and in-silico analysis to study the interaction between phosphate transporter (PHO1), arsenic and phosphate in spinach

An adequate amount of Sulfur (S) is essential for proper plant growth and defence against abiotic stresses including metals and metalloids. Arsenic (As) contamination is increasing in agricultural soils rapidly due to anthropogenic activities. Sulfur deficiency and arsenic stress could be more harmful than these individual stresses alone. To understand the impact of S-deficiency and arsenic (31 ppm Na₃AsO₄ of soil) on ecophysiology, growth, inorganic phosphate level, and proteomic profile of spinach, the present study was conducted. Interaction of arsenic with phosphate transporters, phytochelatins, and glutathione was also analyzed in silico. Comparative 2D MS/MS proteomics helped in the identification of important proteins which might be the key players under S-deficiency and As stress. Upregulation and downregulation of 36 and 21 proteins under As stress; 19 and 36 proteins under S-deficiency; 38 and 31 proteins under combined stress, respectively was observed. A total, 87 proteins subjected to identification via MS/MS ion search were found to be associated with important plant functions. PHO1 abundance was highly influenced by As stress; hence an in-silico homology modeling based molecular docking was performed which indicated high interaction between PHO1 and As/phosphate. Varied proximity of arsenic with phosphate transporters, phytochelatin, and glutathione revealed these components as a potential target of As toxicity/detoxification in Spinach, reflecting sulfur as an important criterion for arsenic tolerance.