Thesis (M.Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 190-202) Also available in print.

Thesis (M.A.)--Zhongguo wen hua da xue shi xue yan jiu suo, 1996. / Includes bibliographical references (p. 227-245).

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 42-47).

The relative importance of stochasticity and adaptation to biodiversity has long been of interest to evolutionary biologists. Multiple, closely related insular populations provide ideal natural experiments with which to determine die relative strength of these two factors. An example of one such system is the threespine stickleback, Gasterosteus aculeaius. Threespine stickleback have predator defenses comprised of heritable lateral bony plates and large spines. Morphologically invariant marine stickleback have colonized freshwater habitats across the northern hemisphere, resulting in multiple independently derived freshwater forms highly variable in predator defenses. The islands of Haida Gwaii (the Queen Charlotte Islands), British Columbia, contain populations of freshwater stickleback that exhibit defensive variability comparable to the entire species, and vary in defensive asymmetry. Previous studies showed that numbers of defensive lateral plates and plate symmetry are positively correlated with the presence of predatory trout on these islands, but the effect of avian predators, another predator of stickleback, on plate number evolution remains unexplored. The purpose of this thesis is to determine whether plate number reduction is a defensive adaptation to avian predation, and to study functional implications of asymmetry in structural defenses from 115 natural populations. Experiments showed that plate number reduction in threespine stickleback enhanced fast-start velocity; a possible advantage to fish being pursued by diving birds with similar swimming speeds. Avian injury frequencies increased in populations as plate numbers increased at low plate numbers, but did not increase in populations wife plate numbers greater than ten. Trout injury frequencies decreased as plate numbers increased among populations, probably due to methodological problems. There were no correlations between avian or trout induced injuries and plate number within populations. Experiments indicated that selective predation of lateral plate numbers in stickleback by captive Hooded Mergansers was weak but insignificant, resulting in a very slight reduction in plate numbers after predation. The degree of fluctuating asymmetry (FA) of defensive structures showed a geographical cline across the archipelago, being elevated in lowland stained ponds, and reduced in clear large lakes. FA of juveniles was not correlated with pH, conductivity, light transmittance, or lake size among populations. Asymmetric individuals did not have reduced survivorship, contrary to predictions from previous studies of FA. However, asymmetry of lateral plates was negatively correlated wife plate number, and asymmetry of plates that provide structural integrity to the defensive spines was greatly reduced relative to ‘non-structural’ plates, supporting fee hypothesis that biomechanically important traits have greater symmetry. Structural plate asymmetry decreased as water clarity, and the chances of capture by predators, increased, and when the degree of overlap between plates and spine supports increased. Plate asymmetry was weakly associated with susceptibility to parasitism, but only where overall plate numbers were low. This supports the hypothesis that FA/fitness correlations are trait and habitat specific, and that sensitivity of asymmetry to developmental instability can be reduced in biomechanically important traits. In conclusion, reduction in armour in stickleback may be adaptive, but there is only weak evidence of selection by avian predators on lateral plates in the wild. Whether armour reduction is a direct adaptation to avoid capture or a cost-minimization strategy is not clear, but repeatability of reduced armour in habitats with diving birds, and the hydrodynamic benefit it provides, suggest the former. The associations between asymmetry and function suggest that asymmetry should be included in comparisons of divergent populations, as it lends insight into the functional implications of morphological diversity. Lastly, because multiple independent Iineages have evolved similar phenotypes in similar habitats in stickleback, this research has reinforced the idea that local adaptation to unique habitats is the driving force of diversification. / Graduate

M.Sc. (Biochemistry) / Plants are constantly exposed to a range of environmental stresses which can be biotic or abiotic in nature. These stresses/threats result in cross-talk between signaling pathways which trigger numerous defense responses. These reactions include activation of defense genes, accumulation of reactive oxygen species (ROS) and biosynthesis of small protective/defensive chemical compounds. The plant metabolome is comprised of primary and secondary metabolites, and while primary metabolites are involved in crucial metabolic processes such as growth and development, the latter play a key role in plant-pathogen interactions (defense). Metabolomics is one of the most recent “omic” technologies and involves the study of metabolites and their metabolic pathways under certain physiological conditions. This provides biological knowledge about the system under study giving insight into the cellular processes that define the phenotype of a cell, tissue or whole organism. In the present study a metabolomic approach was used to elucidate and analyze changes in the metabolism of Arabidopsis thaliana cells and leaves following lipopolysaccharide (LPS) treatment. Camalexin (a phytoalexin) and a group of metabolites known as glucosinolates (phytoanticipins) have been shown to accumulate in response to plant-pathogen and plant-herbivore interactions and were the main focus of the study. A number of studies involving herbivore-induced glucosinolate production have been conducted; however, in terms of microbial attack, studies are limited. The following study therefore provided insight into the effect that LPS treatment has on the biosynthetic pathways for indolic, aliphatic and aromatic glucosinolates....

Induction of phenylpropanoid metabolism in many plants is associated with the induction of plant defence responses. Among these are the accumulation of phenylpropanoid-derived phytoalexins, increase in lignification around infected sites, and the accumulation of wall-bound phenolic compounds. I show in this work, that H11 hybrid cell suspension cultures when treated with either of three elicitors respond with an increase in phenylpropanoid metabolism. Activation proceeds rapidly from PAL and 4CL mRNA accumulation, to a massive increase in extractable PAL enzyme activity and finally there is accumulation of specific phenolic compounds in the cell extracts, culture filtrates, and cell walls. In addition, elicitor treatment causes cells to turn brown, indicative of phenolic compound accumulation. As in other plants, induction is dependent on culture age, is dose dependent, and the kinetics of induction is the same with all three elicitors. Based on the previously established mode of action of PGA lyase as an elicitor, it is concluded that in poplar, as in other plants, defence responses can be induced by elicitors from both fungal and plant cell wall origin. These results illustrate the successful use of plant suspension cultures as a simplified system to study inducible defence responses. In addition, and consistent with the ubiquitous nature of phenolics in poplar, phenylpropanoid metabolism may play an important role in plant defence responses in this species. / Science, Faculty of / Botany, Department of / Graduate

The security arrangements established between Britain, Australia, New Zealand, Malaysia and Singapore, announced in April 1971, are remarkable for their lack of explicit detail and formalised commitment. This vagueness has discouraged a positive assessment of the contribution toward regional security that may be represented by the arrangements, and most academic and popular evaluations have been superficial or simply derogatory. In order to uncover the real intentions of the five participants, and thus establish the effectiveness and credibility of their joint defence system, it was considered necessary to subject to systematic analysis the decision-making processes by which each of the five states arrived at the point of agreement. Although Graham T. Allison's system of analysis was designed to illuminate a crisis situation that bears only a limited resemblance to the kind of almost evolutionary decision-making processes represented by this problem, his trifocal framework was found to be readily applicable. The thesis reports in some detail the analytical proceedings and findings in the case of the British decision-making process, which is considered to be of the greatest interest and importance, and also reports more briefly on the results of similar analyses of the decision-making processes of the other participants. The Allison framework is found to be particularly productive in both identifying and evaluating the intentions of the five powers, and in the second part of the thesis the way in which these intentions have been translated into actual strategic dispositions receives general attention, and the capabilities of the ANZUK forces are compared with the various threats and dangers with which they are likely to be confronted. In conclusion it is found that the original intentions of the five participants have already been outpared and outmoded by certain major shifts in the systemic and subsystemic political environment of Southeast Asia. However, it seems that several of these obsolete functions have been replaced by others that will serve to extend the usefulness of the arrangements beyond the immediate future. / Arts, Faculty of / Political Science, Department of / Graduate

No description available.

M.Sc. (Biochemistry) / During microbial invasion, a variety of defense responses are induced in host plants. In order for host plants to combat potential diseases induced by microbes, they must be equipped with pattern recognition receptors (PRRs) localized at the cell surface, since such receptors enable the perception of conserved microbial epitopes termed microbe/pathogen-associated molecular patterns (M/PAMPs), thereby resulting in the activation of plant innate immunity via M/PAMP-triggered immunity (P/MTI). Lipopolysaccharide (LPS) is the major component of the outer leaflet of the external membrane of Gram-negative bacteria. This thermo-stable lipoglycan is exposed towards the external environment and plays an important role in bacterial adaptation to external surroundings. LPS is recognized as a major M/PAMP in plants, and thus potentiates or elicits defense-related responses such as the production of antimicrobial compounds and the expression of immune response genes. One of the most widely investigated effects of LPS on plants is its ability to prevent and/or suppress the hypersensitive response (HR) induced by an array of bacteria. The HR is a programmed cell death response which ends in a local necrosis of plant tissue, thereby resulting in a reduced number of viable bacteria that can further promote disease progression in the host.

Biotic stress is one of the most serious constraints on rice productivity. Strategy adopting regulators in signal transduction of systemic acquired resistance for conferring long-lasting disease resistance against broad spectrum of pathogens become highly favorable. To achieve this, signal transduction of disease resistance should be well characterized. / OsGPBP1 is a putative G-protein binding protein and interacts with a member of the YchF G-protein subfamily that has not been thoroughly studied in plants, while OsRHC1 is a novel RING zinc finger protein harboring multiple transmembrane domains at the N-half and a unique RING-HC domain at the C terminus. Both of them were induced in the bacterial blight resistant near isogenic rice line upon wounding. Gain-of-function tests in transgenic Arabidopsis thaliana showed that their ectopic expressions are able to trigger the expression of both defense marker genes mediated either by SA- or JA/ET-pathways and led to increased resistance toward the pathogen Pseudomonas syringae pv. tomato DC3000 and both of the two clones seemed to rely on NPR1 (disease resistance key regulator) for function. Furthermore, over-expressions of the two clones in its native system are also able to activate rice defense marker genes. / Suppression subtractive hybridization experiment, using RNA samples from a pair of near-isogenic rice lines either containing the R gene Xa14 (CBB14) or its susceptible recurrent parent (SN1033), were previously performed in our laboratory. Two gene candidates ( OsGPBP1 and OsRHC1) probably encoding two novel types of signal transduction components related to disease resistance are chosen for further analysis. / Cheung, Ming Yan. / "September 2007." / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4555. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 148-168). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.