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Grain Sorghum Proteomics: Integrated Approach toward Characterization of Endosperm Storage Proteins in Kafirin Allelic Variants

Julia E. Cremer, Scott R. Bean, Michael M. Tilley, Brian P. Ioerger, Jae B. Ohm, Rhett C. Kaufman, Jeff D. Wilson, David J. Innes, Edward K. Gilding, Ian D. Godwin
Journal of Agricultural and Food Chemistry 2014 v.62 no.40 pp. 9819-9831
Sorghum bicolor, alleles, endosperm, genetic variation, genotype, grain sorghum, kafirins, loci, mass spectrometry, prolamins, protein bodies, protein composition, protein synthesis, proteomics, reversed-phase high performance liquid chromatography, starch
Grain protein composition determines quality traits, such as value for food, feedstock, and biomaterials uses. The major storage proteins in sorghum are the prolamins, known as kafirins. Located primarily on the periphery of the protein bodies surrounding starch, cysteine-rich β-and γ-kafirins may limit enzymatic access to internally positioned α-kafirins and starch. An integrated approach was used to characterize sorghum with allelic variation at the kafirin loci to determine the effects of this genetic diversity on protein expression. Reversed-phase high performance liquid chromatography and lab-on-a-chip analysis showed reductions in alcohol-soluble protein in β-kafirin null lines. Gel-based separation and liquid chromatography−tandem mass spectrometry identified a range of redox active proteins affecting storage protein biochemistry. Thioredoxin, involved in the processing of proteins at germination, has reported impacts on grain digestibility and was differentially expressed across genotypes. Thus, redox states of endosperm proteins, of which kafirins are a subset, could affect quality traits in addition to the expression of proteins.