Identification, characterization, and modification of differentially expressed genes from soybean

As a major agronomic crop, soybean is the focus of considerable scientific research. Current experiments in genomics promise to provide invaluable resources for future research and crop improvement. However, a true understanding of the developmental processes that take place will be achieved not from knowing what genes are present in soybeans, but rather from knowing when and where these genes are expressed, and understanding how the gene products interact. This thesis examines differentially expressed genes from developing soybean seeds in a variety of ways. First, a seed coat specific subtilisin-like protease is characterized. Not only is the expression of this serine protease limited to the seed coat, but it also accumulates in the intercellular space between a particular layer of parenchymal cells. Also described is the creation of cotyledon-subtracted seed coat suppressive subtractive hybridization libraries, which are used to identify genes expressed specifically in the seed coat of soybean seeds at two developmentally important time points. One time point is immediately prior to the onset of endoreduplication in cotyledons and the other is during seed midmaturation. Finally, experiments are described in which the consequence of expressing a mutant Bowman-Birk trypsin/chymotrypsin inhibitor in soybean is evaluated. The Bowman-Birk inhibitor is an important anti-nutritional factor in soybean seeds, and a factor that prevents the use of raw soybean meal in animal feed. This inhibitor, by virture of site-directed mutations that inactivated it, was expressed in soybean cotyledons. Transgenic soybeans expressing this mutant Bowman-Birk caused a reduction in trypsin and chymotrypsin inhibition by seed extracts despite the continued presence of seed Kunitz trypsin inhibitor