Influence of Sulfur Deficiency on the Expression of Specific Sulfate Transporters and the Distribution of Sulfur, Selenium, and Molybdenum in Wheat

Interactions between sulfur (S) nutritional status and sulfate transporter expression in field-grown wheat (Triticum aestivum) were investigated using Broadbalk +S and -S treatments (S fertilizer withheld) at Rothamsted, United Kingdom. In 2008, S, sulfate, selenium (Se), and molybdenum (Mo) concentrations and sulfate transporter gene expression were analyzed throughout development. Total S concentrations were lower in all tissues of -S plants, principally as a result of decreased sulfate pools. S, Se, and Mo concentrations increased in vegetative tissues until anthesis, and thereafter, with the exception of Mo, decreased until maturity. At maturity, most of the S and Se were localized in the grain, indicating efficient remobilization from vegetative tissues, whereas less Mo was remobilized. At maturity, Se and Mo were enhanced 7- and 3.7-fold, respectively, in -S compared with +S grain, while grain total S was not significantly reduced. Enhanced expression of sulfate transporters, for example Sultr1;1 and Sultr4;1, in -S plants explains the much increased accumulation of Se and Mo (7- and 3.7-fold compared with +S in grain, respectively). Sultr5;2 (mot1), thought to be involved in Mo accumulation in Arabidopsis (Arabidopsis thaliana), did not fully explain patterns of Mo distribution; it was expressed in all tissues, decreasing in leaf and increasing in roots under -S conditions, and was expressed in florets at anthesis but not in grain at any other time. In conclusion, S fertilizer application has a marked impact on Mo and Se distribution and accumulation, which is at least partially a result of altered gene expression of the sulfate transporter family.