Modulation of kernel storage proteins in grain sorghum (Sorghum bicolor (L.) Moench)

Tejinder Kumar, University of Nebraska-Lincoln
Ismail M. Dweikat, University of Nebraska - Lincoln
Shirley Sato, University of Nebraska - Lincoln
Zhengxiang Ge, University of Nebraska - Lincoln
Natalya Nersesian, University of Nebraska-Lincoln
Han Chen, University of Nebraska - Lincoln
Thomas Elthon, University of Nebraska - Lincoln
Scott Bean, Grain Quality and Structure Research Unit, USDA ⁄ ARS
Brian P. Ioerger, Grain Quality and Structure Research Unit, USDA ⁄ ARS
Mike Tilley, Grain Quality and Structure Research Unit, USDA ⁄ ARS
Thomas Clemente, University of Nebraska - Lincoln

Document Type Article

Abstract

Sorghum prolamins, termed kafirins, are categorized into subgroups α, β, and ϒ. The kafirins are co-translationally translocated to the endoplasmic reticulum (ER) where they are assembled into discrete protein bodies that tend to be poorly digestible with low functionality in food and feed applications. As a means to address the issues surrounding functionality and digestibility in sorghum, we employed a biotechnology approach that is designed to alter protein body structure, with the concomitant synthesis of a co-protein in the endosperm fraction of the grain. Wherein perturbation of protein body architecture may provide a route to impact digestibility by reducing disulphide bonds about the periphery of the body, while synthesis of a co-protein, with known functionality attributes, theoretically could impact structure of the protein body through direct association and ⁄ or augment end-use applications of sorghum flour by stabilizing β-sheet formation of the kafirins in sorghum dough preparations. This in turn may improve viscoelasticity of sorghum dough. To this end, we report here on the molecular and phenotypic characterizations of transgenic sorghum events that are downregulated in ϒ- and the 29-kDa α-kafirins and the expression of a wheat Dy10 ⁄ Dx 5 hybrid high-molecular weight glutenin protein. The results demonstrate that down-regulation of ϒ-kafirin alone does not alter protein body formation or impacts protein digestibility of cooked flour samples. However, reduction in accumulation of a predicted 29-kDa α-kafirin alters the morphology of protein body and enhances protein digestibility in both raw and cooked samples.