Endo-β-mannanase is an endohydrolase enzyme responsible for the breakdown of mannan-containing polysaccharides common in the cell walls of many plants. The action of endo-β-mannanase in barley, its optimum temperature and pH for action, temporal and spatial localization, activity in the presence of hormones and sugars and its effect on the seed's mechanical strength were assayed. The development of a spectrophotometric assay for endo-β-mannanase detection was also trialed. The optimum temperature and pH for these experiments were found to be 37℃ and pH 7. Using these parameters, the endo-β-mannanase enzyme was found to be initially localized in the seed coat and moved through to the endosperm over time. The detected level of enzyme activity increased in the presence of gibberellic acid and glucose, or decreased when abscisic acid was added. Similar results were seen when the embryo was removed and the endosperm and seed coat were incubated in hormone- and sugar-containing media. The presence of exogenous endo-β-mannanase did not affect the mechanical strength of the seed but there was a strong correlation between increasing endo-β-mannanase activity and decreasing mechanical strength over time. The spectrophotometric assay for quantifying endo-β-mannanase in extracts showed promise but did not reach fruition due to unexplained sources of variation. The localization and regulation of endo-β-mannanase in barley were similar to those seen in other plants, such as tomato, lettuce and coffee. These findings have biotechnological applications within the brewery industry. By increasing the mobilization of reserves such as mannan, it is thought that the seedling can utilize this secondary carbohydrate source instead of, or at least supplementing, glucose which was mobilized from starch. This will theoretically reduce the starch and glucose lost during the malting period leaving a higher sugar content free for fermentation.

Endo-β-mannanase is an endohydrolase enzyme responsible for the breakdown of mannan-containing polysaccharides common in the cell walls of many plants. The action of endo-β-mannanase in barley, its optimum temperature and pH for action, temporal and spatial localization, activity in the presence of hormones and sugars and its effect on the seed's mechanical strength were assayed. The development of a spectrophotometric assay for endo-β-mannanase detection was also trialed. The optimum temperature and pH for these experiments were found to be 37℃ and pH 7. Using these parameters, the endo-β-mannanase enzyme was found to be initially localized in the seed coat and moved through to the endosperm over time. The detected level of enzyme activity increased in the presence of gibberellic acid and glucose, or decreased when abscisic acid was added. Similar results were seen when the embryo was removed and the endosperm and seed coat were incubated in hormone- and sugar-containing media. The presence of exogenous endo-β-mannanase did not affect the mechanical strength of the seed but there was a strong correlation between increasing endo-β-mannanase activity and decreasing mechanical strength over time. The spectrophotometric assay for quantifying endo-β-mannanase in extracts showed promise but did not reach fruition due to unexplained sources of variation. The localization and regulation of endo-β-mannanase in barley were similar to those seen in other plants, such as tomato, lettuce and coffee. These findings have biotechnological applications within the brewery industry. By increasing the mobilization of reserves such as mannan, it is thought that the seedling can utilize this secondary carbohydrate source instead of, or at least supplementing, glucose which was mobilized from starch. This will theoretically reduce the starch and glucose lost during the malting period leaving a higher sugar content free for fermentation.

Soybean [Glycine max (L.) Merr.] is an important crop worldwide. It has been widely consumed for protein, oil and other soy products. To develop soybean cultivars with greater resistance against pests and improved meal quality, it is important to elucidate the molecular bases of these traits. This dissertation aims to investigate the biochemical and biological functions of soybean genes from four gene families, which are hypothesized to be associated with soybean defense against pests and soybean meal quality. There are three specific objectives in this dissertation. The first one is to determine the function of components in the salicylic acid (SA) signaling pathway in soybean resistance against soybean cyst nematode (Heterodera glycines, SCN). The second one is to determine whether insect herbivory induce the emission of volatiles from soybean, and if so, how these volatiles are biosynthesized. The third objective is to identify and characterize soybean mannanase genes that can be used for the improvement of soybean meal quality. The soybean genome has been fully sequenced, which provides opportunities for cross-species comparison of gene families of interest and identification of candidate genes in soybean. The cloned cDNAs of putative genes were expressed in Escherichia coli to produce recombinant enzymes. Through biochemical assays, these proteins were proved to be soybean salicylic acid methyltransferase (GmSAMT1), methyl salicylate esterase (GmSABP2-1), α[alpha]-farnesene synthase (GmTPS1) and E-β[beta]-caryophyllene synthase (GmTPS2), and endo-β[beta]-mannanase (GmMAN1). Through a transgenic hairy root system harboring overexpression of GmSAMT1 and GmSABP2-1, both of these two genes were evaluated for their biological function related to resistance against SCN. The results showed that the over-expression of GmSAMT1 and GmSABP2-1 in the susceptible soybean background lead to enhanced resistance against SCN. Among four putative soybean mannanase genes, one gene was cloned and characterized. GmMAN1 showed the endo-β[beta]-mannanase hydrolyse activity and can hydrolyze cell walls isolated from soybean seeds. In summary, using comparative and functional genomics, a number of genes involved in soybean defense and meal quality were isolated and characterized. This study provides novel knowledge and molecular tools for the genetic improvement of soybean for enhanced resistance and improved meal quality.