Combined nitrogen and sulphur fertilisation and its effect on wheat quality and protein composition measured by SE-FPLC and proteomics

Soil sulphur deficiency, which is increasingly prevalent in Western Europe, lowers wheat yields, and also affects the gluten quality of the flour. Differences in S availability may change the proportion of S-poor to S-rich gliadins and glutenin subunits. This may cause unpredictable and unwanted variations in wheat quality. The combined effects of nitrogen (N) and sulphur (S) fertilisers and split application of S and N on wheat gluten quality and composition were investigated. The results revealed effects of S fertilisation on dough quality. At high N fertilisation levels significant responses to S fertilisation were found which emphasised the need for precision application of S in intensive wheat production systems. Protein fractionation by SE-FPLC showed that quality differences were associated with changing proportions of high M_r polymeric proteins. Changes in protein composition of salt soluble proteins were also confirmed by proteomics. Glyceraldehyde-3-phosphate dehydrogenase and one of the serpin protein spots increased at high N, combined with the lower S level. The enzymes also increased in samples with increased S fertilisation combined with low N, but was not changed at higher N levels. Furthermore, at high N the serpin protein spot, and also a 27 K protein and one unidentified protein spot decreased with increasing S.