Proteome analysis of two soft-grained wheats of different processing quality: cultivar-specific proteins

Abstract

Proteome analysis was conducted on the grain of 2 closely related soft biscuit-making wheats (Bowie and Rosella cultivars) differing in processing quality. Comparisons between these wheat cultivars were carried out on total wholemeal proteins, extracts with enriched starch granule proteins, and extracts enriched with gliadin storage proteins, with the intention of characterising, identifying, and cataloguing cultivar-specific proteins that could be used for segregation purposes. Initially, 2-dimensional gel electrophoresis was carried out on total wholemeal proteins using a broad range pH 3–10 immobilised pH gradient for the first dimension. Further screening was carried out using a combination of mid to narrow range immobilised pH gradients, including pH 4–7, 5.5–6.7, 5–8, 6–9, and 6–11. Best cultivar-specific protein fractionation was provided by the pH 5–8 range. Altogether, 4 unique cultivar-specific protein spots were excised from the pH 5–8 gels and identified by means of peptide mass fingerprinting, tandem mass spectrometry, or N-terminal sequencing. Starch granule protein extracts were prepared and fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A western blot was performed and probed with an anti-puroindoline-a antibody. Further to this, extracts enriched in gliadin storage proteins were isolated using 70% ethanol and analysed by 2-dimensional gel electrophoresis. The resulting gliadin protein maps showed 18 unique cultivar-specific gliadins. They were excised from the pH 6–9 gels and submitted for N-terminal amino acid sequencing. Overall, this study identified 23 proteins that could be used to distinguish between these closely related cultivars and may provide information on the molecular basis for the differences in processing exhibited by these wheats. The findings reported also contribute to a longer term objective of developing a broad and comprehensive knowledge base of commercial wheats, in regard to protein composition and their inherent processing qualities.