Impact and mechanism of sulphur-deficiency on modern wheat farming nitrogen-related sustainability and gliadin content

Two challenges that the global wheat industry is facing are a lowering nitrogen-use efficiency (NUE) and an increase in the reporting of wheat-protein related health issues. Sulphur deficiencies in soil has also been reported as a global issue. The current study used large-scale field and glasshouse experiments to investigate the sulphur fertilization impacts on sulphur deficient soil. Here we show that sulphur addition increased NUE by more than 20% through regulating glutamine synthetase. Alleviating the soil sulphur deficiency highly significantly reduced the amount of gliadin proteins indicating that soil sulphur levels may be related to the biosynthesis of proteins involved in wheat-induced human pathologies. The sulphur-dependent wheat gluten biosynthesis network was studied using transcriptome analysis and amino acid metabolomic pathway studies. The study concluded that sulphur deficiency in modern farming systems is not only having a profound negative impact on productivity but is also impacting on population health.


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Using large-scale field and glasshouse experiments and transcriptomic and metabolomic analyses to explore the impacts of sulphur fertilization on sulphur-deficient wheat crop and its gluten composition Five cultivars: The wheat cultivars used in the current study, including two cultivars in 2014 and 2015 glasshouse experiments and four cultivars in 2014 field trial, are highly adopted Australian bread wheat cultivars that are widely cultivated in Australia. Flag leaves and developing grains from these cultivars are used.
All plots and pots respectively from 2014 field trial and 2014 glasshouse experiment were harvested at grain maturity. The peduncle parts from Spitfire and Wyalkatchem in three sulphur treatments from three biologically independent replicates in 2014 glasshouse experiment were collected for measurement. The flag leaves of Spitfire in S0 and S30 treatments from three biologically independent replicates in 2015 glasshouse experiment were collected at the stage of flowering for measuring glutamine synthetase (GS) activity. The developing grains from the middle row of the main tiller head of Spitfire at each developing stage in S0 and S30 treatments from three biologically independent replicates in 2015 glasshouse experiment were taken for RNA-seq assay, GS activity assay, and free amino acid assay. For the 2014 field trial, a total of 36 mature grain samples were obtained and analysed from 36 plots for agronomic trait and gluten component, including 4 cultivars (Livingston, Mace, Westonia and Wyalkatchem), 3 sulphur treatments (S0, S30 and S50) and 3 replicate plots for each sulphur treatment. For the 2014 glasshouse experiment, the peduncle sample size and the mature grain sample size for agronomic trait and gluten component are both 18, including 2 cultivars (Spitfire and Wyalkatchem), 3 sulphur treatments (S0, S30 and S50) and 3 replicate pots for each sulphur treatment. The flag leaf samples and developing grain samples collected from 2015 glasshouse experiment were used for mechanism studies, including RNA-seq assay, GS activity assay and free amino acid assay. For RNA-seq assay, grain samples of Spitfire were collected from 3 developing grain stages (7, 14 and 21 DPA) of 2 sulphur treatments (S0 and S30) with 3 biologically independent replicates (or 3 pots), making it a total of 18 samples. For GS activity and free amino acid assay, a total of 6 flag leaf samples of each cultivar (Spitfire or Wyalkatchem) were collected from 2 sulphur treatments (S0 and S30) with 3 biologically independent replicates (or 3 pots) for each sulphur treatment to measure GS activity in flag leaves; a total of 30 developing grain samples of each cultivar (Spitfire or Wyalkatchem) from 5 grain developing stages (7, 14, 21, 28 and 35 DPA) of 2 sulphur treatments (S0 and S30) with 3 biologically independent replicates (or 3 pots) were used for conveying GS activity dynamics in developing grain; a total of 36 developing grain samples of Spitfire were collected from 6 grain developing stages (7, 14, 21, 28, 35 and 42 DPA) of 2 sulphur treatments (S0 and S30) with 3 biologically independent replicates (or 3 pots) to extract free amino acid from developing grain. The flag leaf samples for measuring GS activity as well as the developing grain samples for conveying GS activity dynamics and extracting free amino acid were subject to the commonly used sample subpooling strategy, making it 2 pooled flag leaf samples of each cultivar for measuring GS activity in flag leaves, 10 pooled developing grain samples of each cultivar for conveying GS activity dynamics in developing grains, and 12 pooled developing grain samples of Spitfire for extracting free amino acid from developing grain, followed by 3 technical repeats for each.
The grain yield and protein yield of the sample from 2014 field trial were measured after harvesting and threshing, collected by the staff in Katanning research station of Department of Primary Industries and Regional Development.
The grain yield and peduncle traits of the sample from 2014 glasshouse experiment were measured after harvesting, collected by the author Zitong Yu. The nitrogen-use efficiency for the sample from 2014 field trial and 2014 glasshouse experiment was determined by the grain yield or protein yield produced by per kg of nitrogen applied, calculated as the grain yield or protein yield divided by the amount of N applied at 25 kg/ha.
The sample from 2014 field trial was collected when the grain was mature. For the sample from 2014 and 2015 glasshouse experiments, each pot was watered every morning with demineralized water. The flag leaf from 2015 glasshouse experiment was collected at flowering time, and the developing grains from the middle row of the main tiller head of cultivar Spitfire in 2015 glasshouse experiment were collected at 7-day intervals, with sample collection starting at 7 days post-anthesis (DPA) and ending at 42 DPA, including 7, 14, 21, 28, 35, and 42 DPA.
No data exclusions.
Three biologically independent replicates were used in this study.
The pots in 2014 and 2015 glasshouse experiments were placed based on randomized complete block design. The sample from each pot was collected randomly.
The samples from 2014 and 2015 glasshouse experiments were collected randomly.