Effects of nitrogen nutrition on the synthesis and deposition of the ω-gliadins of wheat.
BACKGROUND AND AIMS
The ω-gliadin storage proteins of wheat are of interest in relation to their impact on grain processing properties and their role in food allergy, particularly the ω-5 sub-group and wheat-dependent exercise-induced anaphylaxis. The ω-gliadins are also known to be responsive to nitrogen application. This study therefore compares the effects of cultivar and nitrogen availability on the synthesis and deposition of ω-gliadins in wheat grown under field conditions in the UK, including temporal and spatial analyses at the protein and transcript levels.


METHODS
SDS-PAGE, western blotting and N-terminal amino acid sequencing were used to compare the patterns of ω-gliadin components in mature grain of six British wheat (Triticum aestivum) cultivars and their accumulation during the development of grain grown in field plots with varying nitrogen supply. Changes in gene expression during development were determined using real-time reverse transcription-PCR (RT-PCR). Spatial patterns of gene expression and protein accumulation were determined by in situ hybridization and immunofluorescence microscopy, respectively.


KEY RESULTS
Two patterns of ω-gliadins were identified in the six cultivars, including both monomeric 'gliadin' proteins and subunits present in polymeric 'glutenin' fractions. Increasing the level of nitrogen fertilizer in field plots resulted in increased expression of ω-gliadin transcripts and increased proportions of ω-5 gliadins. Nitrogen supply also affected the spatial patterns of ω-gliadin synthesis and deposition, which were differentially increased in the outer layers of the starchy endosperm with high levels of nitrogen.


CONCLUSIONS
Wheat ω-gliadins vary in amount and composition between cultivars, and in their response to nitrogen supply. Their spatial distribution is also affected by nitrogen supply, being most highly concentrated in the sub-aleurone cells of the starchy endosperm under higher nitrogen availability.
['Wan|Yongfang|Y|', 'Gritsch|Cristina Sanchis|CS|', 'Hawkesford|Malcolm J|MJ|', 'Shewry|Peter R|PR|']
D000707:Anaphylaxis D002523:Edible Grain D056625:Endosperm D018506:Gene Expression Regulation, Plant D005903:Gliadin D006801:Humans D017403:In Situ Hybridization D009584:Nitrogen D009928:Organ Specificity D013213:Starch D014908:Triticum
nitrogen ω-gliadin Wheat storage protein Triticum aestivum RNA in situ hybridization immunolocalization protein bodies wheat allergy