Sulfate assimilation pathway in plants. ATPS, ATP sulfurylase; APS, adenosine-5′-phosphosulfate; APK, APS kinase; PAPS, 3′-phosphoadenosine-5′ phosphosulfate; APR, APS reductase; SIR, sulfite reductase; SAT, Ser acetyltransferase; OAS, O-acetyl-Ser; OAS-TL, OAS (thiol)lyase; γ-EC, γ-glutamyl-Cys; γ-ECS, γ-EC synthetase; GSH, red. glutathione; GSHS, GSH synthetase; GSSG, ox. glutathione; Fd, ferredoxin.