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. 2025 Dec 3;16:1714617. doi: 10.3389/fpls.2025.1714617

Figure 2.

Diagram illustrating metabolic pathways in plants. Panel A shows nitrogen assimilation from nitrate to ammonium, then to glutamine and glutamate, leading to amino acids and proteins. Panel B outlines the sulfur assimilation pathway from sulfate to sulfite and sulfide, forming cysteine, methionine, and proteins. Panel C describes selenium assimilation from selenate to selenite and selenide, forming selenocysteine, SeMet, and selenoproteins. Each pathway includes enzymes and intermediates, with arrows indicating reaction sequences.

Schematic diagram showing ubiquitous nature of pathways involved in the assimilation of N, S, Se required for amino acid synthesis. (A) Nitrogen assimilation in roots follows sequential reduction into nitrite and ammonium which is then incorporated into amino acids. (B) Sulphur assimilation also follows same sequential reduction into sulfite and sulfide before synthesis of S-containing amino acids primarily cysteine and methionine. Lastly, (C) Selenium assimilation follows the sequential reduction into selenite, selenide and finally used to synthesize selenocysteine and selenomethionine which in-turn is incorporated into selenoproteins.