Increased wheat protein content via introgression of a HMW glutenin selectively reshapes the grain proteome.

Introgression of a high molecular weight glutenin subunit (HMW-GS) allele, 1Ay21*, into commercial wheat cultivars increased overall grain protein content and bread-making quality, but the role of proteins beyond this HMW-GS itself were unknown. As well as increased abundance of 1Ay HMW-GS, 115 differentially accumulated proteins (DAPs) were discovered between three cultivars and corresponding introgressed near-isogenic lines (NILs). Functional category analysis showed that the DAPs were predominantly other storage proteins, and proteins involved in protein synthesis, protein folding, protein degradation, stress response and grain development. Nearly half the genes encoding the DAPs showed strong co-expression patterns during grain development. Promoters of these genes are enriched in elements associated with transcription initiation and light response, indicating a potential connection between these cis-elements and grain protein accumulation. A model of how this HMW-GS enhances the abundance of machinery for protein synthesis and maturation during grain filling is proposed. This analysis not only provides insights into how introgression of the 1Ay21* improves grain protein content, but also directs selection of protein candidates for future wheat quality breeding programmes.