As a plant molecular biologist, my research has focused on the regulation of seed development, with particular emphasis on maize endosperm and the synthesis of maize seed storage proteins, or zeins. Storage proteins, such as zeins, are the most abundant proteins in the seed, and as such they are the principal determinants of the protein nutritional quality. Storage proteins are generally deficient in several amino acids that are required in human and livestock diets. In maize, the most limiting amino acids are lysine and tryptophan. Consequently, increasing the levels of essential amino acids, such as these, has long been a goal of plant breeders and cereal chemists. We have used a molecular genetic approach to investigate the biology of seed storage protein synthesis. These studies have attempted to define the structure of zein proteins, the mechanisms by which they are synthesized and organized into protein bodies in endosperm cells, and the genes that regulate these processes. We have found that the protein synthesis factor, eEF1A, provides a rather precise indicator of the protein-bound lysine in maize endosperm, and research is in progress to understand the biological basis of this relationship as well as create genetic strategies for increasing the content of this protein. We are also investigating the role of DNA endoreduplication in endosperm development. As is true of many metabolically active tissues in plants, endosperm cells undergo multiple rounds of chromosome replication coincident with the onset of starch and storage protein synthesis. Our current research is directed at understanding the physiological consequences of endoreduplication in developing endosperm and the molecular mechanism by which it occurs.
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