No description available.

No description available.

The aim of this work was to isolate the gene encoding a bifunctional a-amylase inhibitor/endochitinase protein from the seeds of Coix lachryma-jobi, a tropical cereal. Prior to this study, it had been demonstrated that this bifunctional protein had anti-insect and possibly anti-fungal properties. Consequently the gene could potentially be used to confer insect and fungal resistance in transgenic plants. A multifunctional approach was undertaken to isolate the a-amylase inhibitor/endochitinase cDNA and genomic sequences, involving three main strategies. Immunoscreening a Coix cDNA expression library with antibodies raised against a wheat germ endochitinase protein resulted in the isolation of three immunopositive clones. These cDNA's, were sequenced and one characterised as a seed storage protein, named a-coixin. Despite extensive searches of the appropriate databases, the function of the other two are as yet unknown. Another strategy was the production of polyclonal antibodies, raised against a glutathione S- transferase-a-amylase inhibitor fusion peptide. It was envisaged that these antibodies could be used to isolate the gene of interest following immunoscreening of the Coix cDNA expression library. Polyclonal antibodies were successfully elicited against the glutathione S- transferase moiety, but could not detect the a-amylase inhibitor protein when assayed. Using the polymerase chain reaction, amplification of the a-amylase inhibitor coding sequence was attempted from Coix genomic DNA, cDNA and a Coix seed cDNA library. PGR product were successfully amplified from genomic DNA and the cDNA library. Further characterisation of these product revealed that they were a result of non specific amplifications. Further work required to isolate the a-amylase inhibitor gene is discussed.

The greater part of this work describes the biochemical and morphological changes accompanying grain development in cereals. Attention is focussed on those aspects most likely to be involved in the regulation of grain yield and composition. Thus, since starch is the major component of grain yield much of the work is concerned with the developmental enzymology of carbohydrate synthesis. The composition, properties and structure of the developing starch granules and amyloplasts have also been described. Grain development is associated with a range of catabolic processes and a number of enzymes active in carbohydrate degradation has been identified. Although oxygen levels in the developing endosperm are unknown, recent work suggests that the mitochondria present are fully func- tional. It is possible that oxygen required for grain respiration is derived from pericarp photosynthesis. At the same time this tissue may fix carbon dioxide derived from endosperm respiratory processes. Thus, the pericarp may be involved in the overall control of endosperm metabolic activity. Studies of endosperm cell division indicate that this continues for more than half the developmental period, later divisions producing mainly aleurone cells. Hence, stimulation of endosperm cell division early in development will increase the yield of carbohydrate whereas at later stages it will increase the yield of protein. Further studies describe the pattern of mineral ion accumulation, the growth and nutrition of the develop - ing embryo and the morphological changes in the crease region through which nutrients move from the vascular tissue of the pericarp to the endosperm. A second group of papers is concerned with the control of a- amylase and polyphenol oxidase activity during cereal grain germination. Finally, there is a small group of papers describing research on the properties of photosynthesising tissues including marine algae.

M.Tech.

Research investigates the chemical basis for Fusarium head blight (FHB) resistance and initiating development of a screening test for resistant wheat genotypes. The focus is on minimizing cost of screening and gaining chemical approach against FHB. Wheat bran/agar plates (8% bran, w/v) prepared from hard red spring wheat with different susceptibility to FHB were inoculated with F. graminearum. Fusarium plaque diameters and ergosterol levels after 4 days of growth were significantly lower (p< 0.05) on plates prepared from genotypes with low FHB susceptibility than from high FHB susceptible genotypes. F. graminearum growth was lower, when methanol-soluble compounds (MSC) extracted from a low FHB susceptibility genotype, Glenn, were added to high susceptibility genotype, Samson. Wheat bran/agar plates enriched with linoleic acid significantly (p<0.05) reduced the growth rate of F. graminearum in both Glenn and Samson genotypes. Oxygenated fatty acids, including monohydroxy- and dihydroxy- fatty acids were identified in the MSC.

No description available.

No description available.

No description available.

No description available.