Citation: Zhang, W., Sangtong, V., Peterson, J., Scott, M.P., Messing, J. 2013. Wheat glutenin alters protein body structure in maize but not levels of endogenous storage proteins. Planta. 237:1465-1473. Interpretive Summary: Cereal grains accumulate specific families of proteins that confer nutritional and functional properties to products made from them. The grains of wheat and maize have very different properties leading to different uses. Wheat accumulates a family of proteins called glutenins that are missing from corn, but are similar to a family in corn called beta/gamma zeins. We investigated the functional relationship between these families of proteins by adding a gene that causes wheat glutenin to accumulate to normal corn and corn lacking beta/gamma zeins. Examination of the resulting grains suggested that the maize and wheat proteins are not functionally equivalent, but both contribute to grain structure at the subcellular level. This information about the functional roles of these proteins establishes limits on the types of modifications likely to be tolerated in grain with modified protein content and will help scientists engineer grains with improved nutritional and functional properties.
Technical Abstract: Cereal grains are an important nutritional source of amino acids for humans and livestock worldwide. They belong to three subfamilies of grasses or Poaceae. Wheat, barley, and oats belong to the subfamily Pooideae, rice to the Ehrhartoideae, and maize, millets, sugarcane, and sorghum to the Panicoideae. Seeds, however, are largely void of free amino acids because they are stored during dormancy in specialized proteins, which are also called storage proteins. The major class of storage proteins in cereals is called prolamins because of the preponderance of proline and glutamine and has originated from a subclass, called glutenins. Prolamins are synthesized at the endoplasmic reticulum during seed development and deposited into subcellular structures of the immature endosperm, called protein bodies. Prolamins have diverged during the evolution of the grass family in their structure and their properties. For instance, glutenins are unique to the Pooideae and not present anymore in Panicoideae. Therefore, we used the expression of wheat glutenin-Dx5 in maize to examine its interaction with maize prolamins during endosperm development.