Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 197-236). Also available in electronic version. Access restricted to campus users.

The discovery of the Arabidopsis ttg1 mutant almost three decades ago provided a unique opportunity for the study of how several cell fates and organ identity pathways are co-regulated. Besides showing a lack of flavonoid based pigments, the pleiotropic ttg1 mutant is also deficient for the development of several epidermal characters including plant hair cells (trichomes), the non-hair cells of the root and the mucilage-secreting cells of the seed coat epidermis. Ectopic expression of the maize R bHLH transcriptional regulator of the flavonoid pigment pathway could completely suppress all the ttg1 mutant phenotypes, providing the first clue to the nature of the control mechanisms governing TTG1-dependent traits. Because it was established that a bHLH and a Myb protein are required for the regulation of anthocyanin pigment production in several plant species and an Arabidopsis Myb gene was necessary for trichome initiation, the existence of bHLH and Myb proteins that would regulate all the TTG1-dependent developmental pathways was hypothesized. This study works towards the elucidation of the transcriptional control mechanisms that regulate the TTG1-dependent developmental pathways. The identification and characterization of a key regulator, EGL3, uncovered the redundant nature of bHLH proteins operating under the TTG1 regulatory umbrella. As a result, bHLH regulators were assigned to all TTG1-dependent epidermal cell fate pathways and new roles for previously identified bHLH proteins were revealed. Roles suggested in the literature for Arabidopsis Myb factors suspected of regulating the flavonoid pigment pathway were at odds with findings from other plant models. Analysis of Myb loss-of-function RNAi lines and TTG1:GR and GL3:GR fusion lines presented here provides a clarified understanding of the regulation of anthocyanin biosynthesis by the Myb/bHLH/WDrepeat complex in Arabidopsis. Missing from the combinatorial complex model is the Myb component controlling the differentiation of the seed coat epidermis. Work presented here characterizes Myb5 as the primary Myb regulator of this differentiation pathway and defines a new role for TT2 as partially redundant with Myb5 for testa epidermis development. Myb5 also plays a minor role in trichome development and PA biosynthesis. Thus pleiotropy among the TTG1-dependent Myb regulators previously unobserved is first noted here. A more complete Myb/bHLH combinatorial transcription factor network model for the regulation of the TTG1-dependent pathways is proposed based on the results of work presented in this dissertation. / text

Software testing is the most commonly used methodology for validating quality of software systems. Conceptually, testing is simple, but in practice, given the huge (practically infinite) space of inputs to test against, it requires solving a number of challenging problems, including evaluating and reusing tests efficiently and effectively as software evolves. While software testing research has seen much progress in recent years, many crucial bugs still evade state-of-the-art approaches and cause significant monetary losses and sometimes are responsible for loss of life. My thesis is that a unified, bi-dimensional, change-driven methodology can form the basis of novel techniques and tools that can make testing significantly more effective and efficient, and allow us to find more bugs at a reduced cost. We propose a novel unification of the following two dimensions of change: (1) real manual changes made by programmers, e.g., as commonly used to support more effective and efficient regression testing techniques; and (2) mechanically introduced changes to code or specifications, e.g., as originally conceived in mutation testing for evaluating quality of test suites. We believe such unification can lay the foundation of a scalable and highly effective methodology for testing and maintaining real software systems. The primary contribution of my thesis is two-fold. One, it introduces new techniques to address central problems in both regression testing (e.g., test prioritization) and mutation testing (e.g., selective mutation testing). Two, it introduces a new methodology that uses the foundations of regression testing to speed up mutation testing, and also uses the foundations of mutation testing to help with the fault localization problem raised in regression testing. The central ideas are embodied in a suite of prototype tools. Rigorous experimental evaluation is used to validate the efficacy of the proposed techniques using a variety of real-world Java programs. / text

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

published_or_final_version / abstract / toc / Botany / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

No description available.

No description available.