Gene Expression and Genome Structure Relevance in an Applied Project on Wheat Quality

Abstract

Wheat is one of the foundations of the human diet and human society by a number of criteria: total calories consumed, total protein consumption, total acreage planted, and total harvested tonnage. In addition, wheat is unique in the wide range of products produced from its seed. This last feature is due to the visco-elastic properties of wheat doughs and is largely conferred by a small group of seed proteins, the high- molecular-weight (HMW) glutenins. The HMW-glutenin genes and their encoded polypeptides’ contributions to dough elasticity are thus of great economic significance. The importance of these proteins is also evident from the large literature on their structure and function. It can also be argued that the genes for these proteins are of higher priority to wheat breeders than any other single locus or set of loci. In the U.S. their relative importance in breeding programs has only declined because the existing favorable alleles and gene combinations have already been effectively fixed in many sets of germplasm. However, breeders commonly find otherwise favorable lines still lacking desired features. A number of laboratories worldwide, including our own, are trying to determine the molecular basis of wheat dough visco-elasticity in order to both understand the phenomenon and how to control it for improved wheat varieties. This involves the creation of new genetic variation such as changes in the number of genes and the creation of new loci. The knowledge of the molecular basis of visco-elasticity and the ability to control gene expression will, in the long term, lead to directed modification of cultivars for specific markets. During these experiments we find ourselves dealing with questions related to not only many basic questions in protein chemistry, protein structure, and rheology, but also many of the current questions about gene expression and genome organization. This connection to so many different topics can raise the question of the relationship between basic and applied science. How a very applied project has relevance to questions of basic plant biology will be described and discussed along with the prospects for genetic engineering of novel wheat and other cereal varieties.