Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The evolutionary history of the African tribe Tragelaphini (spiral-horn antelope) is controversial. Past phylogenetic relationships among species were based on morphology or limited fossil evidence and are in conflict with mitochondrial DNA sequencing studies that have been conducted more recently. Although the group is distinguished from other African ungulates by the presence of spirally-twisted horns, the nine recognized extant species differ considerably in morphology, feeding habits and their habitat preference. The present study aims to resolve the phylogenetic uncertainties of the Tragelaphini using nuclear DNA sequence data derived from four independent DNA loci (MGF, PRKCl, SPTBN and THY). These data were combined with all previously published DNA sequences to produce a molecular supermatrix comprising approximately 6000 characters. Both parsimony and model based phylogenetic analyses of the nuclear DNA support the associations resulting from the analysis of mitochondrial genes. These findings suggest that the morphological characters previously used to delimit species within the group are subject to convergent evolution. The molecular phylogeny presented herein suggests that early members of Tragelaphini diverged from the other bovids during the mid-Miocene approximately 15.7 million years before present (MYBP). The common nyala (Tragelaphus enqest; and lesser kudu (Tragelaphus imberbis) representing the most basal species, separated from the other tragelaphids approximately 7.1 MYBP. This was subsequently followed by the radiation of those species adapted to a more tropical environment and they include the mountain nyala (Tragelaphus buxtom), bongo (Tragelaphus euryceros), sitatunga (Tragelaphus spekel) and bushbuck (Tragelaphus scriptus), and the arid adapted clade comprising the giant eland (Taurotragus derbianus), common eland (Taurotragus oryx) and greater kudu (Tragelaphus strepsiceros). It is thought that this split occurred at the Miocene-Pliocene boundary approximately 5.4 MYBP. The timing of evolutionary events within the tribe suggests climatic oscillations and subsequent biotic shifts as the major driving forces underpinning speciation in the tribe Tragalaphini. / AFRIKAANSE OPSOMMING; Die evolusionêre geskiedenis van die ras Tragelaphini (spiraalhoringwildsbokke) is kontroversieël. Vorige filogenetiese verwantskappe tussen die spesies is gebaseer op morfologie of beperkte fossiel bewyse. Meer onlangse studies, gebaseer op mitochondriale ONS nukleotieddata, is in teenstryding met baie van die evolusionêre hypotese afkomstig van morfologiese studies. Alhoewel die groep van die ander hoefdiere uitgeken kan word deur die aanwesigheid van spiraalvormige horings, verskil die nege hedendaagse spesies grootliks ten opsigte van morfologie, voedingswyse en habitat. Die hoof doelwit van hierdie studie was om die filogenetise verwantskappe tussen die Tragelaphini spesies te ontleed deur gebruik te maak van nukluêre ONS nukleotieddata afkomstig van vier onafhanklike ONS merkers (MGF, PRKCl, SPTBN en THY). Die data verkry is saamgevoeg by vorige gepubliseerde ONS nukleotidedata om 'n "supermatris" van sowat 6000 karakters te produseer. Parsimonie en modelgebaseerde filogenetise analise van die nukluêre ONS nukleotieddata het ooreengestem met die resultate van vorige mitochondriale studies. Hierdie bevindings dui daarop dat die morfologiese karakters wat voorheen gebruik is om die evolusionêre verwantskappe tussen die Tragelaphini spesies te ontleed onderhewig is aan konvergente evolusie. Die molekulêre filogenie wat hierin beskryf word stel voor dat die ras Tragelaphini gedurende die mid- Miocene, omtrent 15.7 miljoen jaar (MJ) gelede van die ander lede van die subfamilie Bovinae geskei het. Tragelaphus angasi en Tragelaphus imberbis, die mees basale spesies in die filogenie, het omtrent 7.1 MJ gelede van die ander lede van die Tragelaphini geskei. Hierdie skeiding is gevolg deur 'n split tussen die spesies aangepas vir 'n meer tropiese habitat (Tragelaphus buxtoni, Tragelaphus euryceros, Tragelaphus spekei en Tragelaphus scriptus) en die spesies aangepas vir 'n droë habitat (Taurotragus derbianus, Taurotragus oryx en Tragelaphus strepsiceros) Hierdie finale skeiding het gedurende die Miocene-Pliocene oorgang plaasgevind. Die tydsberekening van die evolusionêre gebeurtenisse wat binne die Tragelaphini ras plaasgevind het, gekoppel aan paleoklimaatdata, dui aan dat veranderinge in klimaat en die geassosieerde habitatveranderinge verantwoordelik was vir die spesiasie patroon wat ons vandag in die Tragelaphini ras waarneem.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Another important gene, heat shock factor (MeHSF) was also cloned using homology based PCR because it was suggested to participate in the transcriptional regulation of many essential components of ovarian maturation including vitellogenin gene and several proteins for hormones metabolism. The complete cDNA sequence of MeHSF was 2211 bp in length, which encoded a 622 amino acid protein. The translated MeHSF protein shared high similarity with those of other species, especially in the N terminal region. RT-PCR showed that MeHSF was universally expressed in most of the female tissues investigated including ovary, central nervous system, heart, gill, gut and muscle. However, its expression was not detectable in eyestalk and hepatopancreas. MeHSF was highly expressed in immature ovaries, and decreased dramatically with the progress of ovarian maturation. Since the synthesis of vitellogenin in ovary showed an opposite trend, the result suggested that MeHSF probably functioned as a transcriptional repressor to vitellogenin. Four HSFs isoforms generated from alternative splicing were obtained in immature ovaries, suggesting a possible universal role of HSF in coordinating transcription of different target genes during shrimp ovarian maturation. / As an important component of enzymatic scavenger systems, glutathione peroxidases (GPx) play important roles in maintaining the balance between reactive oxygen species (ROS) production and cellular scavenging ability. In this research, a full length GPx gene (MeGPx) which had been identified using RAP-PCR previously was cloned and characterized. MeGPx might play a pivotal role in preventing oocytes from oxidative damage and balancing ROS production. The present data on shrimp GPx provides insights on the regulation of ROS in the ovarian maturation process. / Four candidate genes possibly participating in the regulation of ovarian maturation were obtained by random sequencing the libraries, including metallothionein, two zinc finger proteins and member 4 of wingless-type MMTV integration site family (WNT4). The zinc finger protein containing a plant homeodomain, was only expressed in the eyestalk of female with immature ovaries, but not that of female with early mature and mature ovaries. The full length cDNA sequence of shrimp WNT4 gene (MeWNT4) was obtained using RACE technique. RT-PCR showed that the expression of MeWNT4 in eyestalk decreased with the maturation of shrimp ovaries. Interestingly, MeWNT4 was strongly expressed in the central nervous system and gut of both female and male shrimp. It was suggested that WNT4 could antagonize the testis determining factor (SRY), and play an essential role in suppressing the formation of testis, and at the same time, controlling of female development. Thus, the identification WNT4 from crustacean would contribute to our understanding on the sex determination mechanism. / In this thesis, two genes, heat shock protein 90 and heat shock factor, possibly playing important roles in shrimp ovarian maturation were identified and characterized. / Shrimp farming plays an important economic role in Southeast Asian countries. Yet further development of this industry is seriously restricted by the environmental deterioration and the prevalence of fetal diseases. Moreover, the failure of sexual maturation of cultured female shrimp forms a bottleneck to the further development of shrimp aquaculture. With the aim to produce shrimp without totally depending on the wild stocks, many studies have been focused on the endocrine regulation of shrimp ovarian maturation. In order to enhance our understanding on the molecular events occurred during ovarian maturation, in this research, several candidate genes are identified, and their potential roles in ovarian maturation are studied in the shrimp Metapenaeus ensis. / Since heat shock protein 90 gene is one of the essential components of steroid hormone signal cascades in vertebrates, it was cloned and isolated by homology cloning strategy. The complete cDNA sequence of shrimp Hsp90 ( MeHsp90) was 2524 by in length, which encoded a 720 amino acid polypeptide. The MeHsp90 coding region was interrupted by four introns. MeHsp90 was differentially expressed in eyestalk, ovary and hepatopancreas at different ovarian maturation stages, and consistently expressed in other tissues including heart, gill, gut, muscle and central nervous system. In vitro ovary explant assay revealed that MeHsp90 expression in immature ovary could be induced by the addition of exogenous estradio1-17beta. MeHsp90 was highly expressed in pre-vitellogenic oocytes, and its expression decreased with the progress of maturation, and finally stopped in late-vitellogenic oocytes. The co-regulation of MeHsp90 and vitellogenin by estrogen hormone suggested a possible regulatory role of Hsp90 in vitellogenin synthesis of the shrimp. / Wu, Long Tao. / "May 2008." / Adviser: Chu Ka Hou. / Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1409. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 92-113). / 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.

Ma, Ka Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 88-103). / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEDGEMENTS --- p.vii / CONTENTS --- p.ix / LIST OF TABLES --- p.xi / LIST OF FIGURES --- p.xii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Molecular phylogenetics --- p.1 / Chapter 1.2 --- Phylogeny of the penaeoid shrimps --- p.2 / Chapter 1.2.1 --- Interfamilial relationships of Penaeoidea --- p.3 / Chapter 1.2.2 --- Ingergeneric relationships of Penaeidae --- p.8 / Chapter 1.2.3 --- Interspecific relationships of Penaeus s.l --- p.11 / Chapter 1.3 --- Molecular markers for decapods phylogenetics studies --- p.14 / Chapter 1.3.1 --- Mitochondrial markers --- p.14 / Chapter 1.3.2 --- Nuclear markers --- p.16 / Chapter Chapter 2 --- Molecular phylogeny of superfamily Penaeoidea / Chapter 2.1 --- Introduction --- p.19 / Chapter 2.2 --- Materials and methods --- p.21 / Chapter 2.3 --- Results --- p.28 / Chapter 2.4 --- Discussion --- p.40 / Chapter 2.5 --- Conclusions --- p.48 / Chapter Chapter 3 --- Molecular phylogeny of genus Penaeus sensu lato / Chapter 3.1 --- Introduction --- p.50 / Chapter 3.2 --- Materials and methods --- p.50 / Chapter 3.3 --- Results --- p.56 / Chapter 3.4 --- Discussion --- p.74 / Chapter 3.5 --- Conclusions --- p.84 / Chapter Chapter 4 --- General conclusions --- p.85 / References --- p.88

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Lipochitooligosaccharides (LCOs) are molecules secreted by rhizobia during the establishment of rhizobia-legume N2-fixing symbiosis. Some recent reports have shown that there are physiological effects on host and non-host rhizobia after LCO treatment. However, the cellular mechanisms underlying these observations are not known. Therefore, the study was aimed at assessing phenotypic changes by measuring photosynthesis, leaf area and dry weight on a non-host plant (tobacco). Our results did not show any significant physiological changes following LCO treatment. We also wanted to explore the molecular basis of changes in the plant cell by looking at gene and protein profiling following LCO treatment in a natural host plant (soybean) using real-time RT-PCR and SDS-PAGE. To do so, a reproducible stimulation method for soybean seed germination by LCO was successfully developed. The results obtained on soybean did not reveal significant differences in gene expression between water and LCO-treated seeds for the genes cdc2, WASI, ICL1 and 14-3-3 studied. In addition, LCO treatment did not change the protein profile compared to the water control in a significant way.

Please read the summary in the section 00front of this document. / Thesis (PhD)--University of Pretoria, 2005. / Genetics / Unrestricted

No description available.

published_or_final_version / abstract / toc / Microbiology / Master / Master of Philosophy

published_or_final_version / Paediatrics / Master / Master of Philosophy