Based on the recommendations of both the 1993 Reintroduction biology of Australasian Fauna Conference and the 1994 Rock Wallaby Symposium, captive-bred Yellow footed rock wallabies were reintroduced into areas of their former ranges in both South Australia and Queensland

Includes bibliographical references (l5 leaves) The aim of the work presented in this thesis was to develop molecular genetic markers for YD2 (the gene in barley which provides protection against barley yellow dwarf luteovirus) which could be used for the marker assisted selection of the gene in breeding programs and enable the gene to be cloned via a map-based approach.

<p>The aim of this work was to understand the molecular mechanism of translation and the mechanism of translation termination, in particular. Cleavage of peptidyl-tRNA and peptide release terminates translation of mRNA on the ribosome. In prokaryotes, three release factors (RFs) are involved in this process. RF1 and RF2 recognise the three stop codons on mRNA and induce hydrolysis of the ester bond in peptidyl-tRNA. RF3 accelerates the rate of RF1 and RF2 recycling between ribosome in a GTP-dependent manner. We have clarified the mechanism of action of peptide release factor RF3. In the cell, free RF3 is in the GDP conformation. When RF3∙GDP binds to ribosome in complex with RF1 or RF2, these ribosome complexes act as guanine exchange factors for RF3 by inducing rapid dissociation of GDP. If, and only if, the peptide has been removed from tRNA, GDP is quickly replaced by GTP. Binding of GTP to RF3 induces a conformation of the factor with high affinity for the ribosome, which forces RF1 or RF2 to rapidly dissociate. Subsequent hydrolysis of GTP on RF3 induces a factor conformation with low affinity for the ribosome and rapid release of RF3∙GDP. It was further shown how the position of peptidyl-tRNA on the ribosome and the presence or absence of its peptide regulates the binding and GTPase activity of translation factors IF2, EF-G and EF-Tu. The result explains how idling GTPase hydrolysis and negative interference between different translation factors are minimized in living cells. The present biochemical observations, in conjunction with cryo-EM results, lead to new proposals for the role of hybrid sites in translocation of tRNAs, recycling of RF1 and RF2 by RF3 and recycling of post-termination ribosomes back to a new round of initiation.</p>

Yellow starthistle (Centaurea solstitialis L.) is an introduced Asteraceae that has become established on 10 million acres in the Pacific Northwest and California. This weed functions as an annual or short-lived perennial and depends on seeds for reproduction. Strategies of control that reduce plant fitness or lower seed production or viability may help limit the rate of spread of yellow starthistle. Previous work has shown that grazing and mowing can influence seed production. This study tested the hypothesis that proper timing and frequency of defoliation can reduce the number and viability of seeds produced. The study was conducted in Umatilla County, Oregon using a randomized block design with 4 replications of each of 4 defoliation treatments: (1) single defoliation at the bolting stage; (2) single defoliation at the bud stage; (3) two defoliations, once at the bolting stage and again at the bud stage; (4) non-defoliated control. Each of 4 blocks consisted of a 12 x 12 m area, with 16 plots measuring 3 x 3 m. Plants were defoliated at ground level using a gas-powered string-type mower. Response measurements were collected at the end of the growing season (September) following potential regrowth and included: (1) number of seedheads per plant; (2) number of seeds per seedhead; (3) number of seeds per plant; (4) number of seeds m⁻², (5) seed viability (% germination rates). Supporting measurements included: seedhead diameter; plant height, number of branches per plant; pre-dawn xylem pressure; soil moisture; and documentation of 5 biological control insect species. A single defoliation at bolting resulted in fewer seeds per seedhead, and fewer seeds per plant than non-defoliated controls. A single defoliation at the floral bud stage or repeated defoliation (bolting and again at the bud stage) resulted in equally fewer seeds per plant and fewer seeds m⁻² compared to non-defoliated controls. There was no statistical difference in percent germination of seeds among treatments. Defoliation had no effect on the infestation rates of seedheads by biological control insects. A second study examined nutrient content of yellow starthistle during 6 phenological stages from sites in Union, Baker and Umatilla Counties, Oregon during each of 2 years. Acid detergent fiber, lignin, cellulose and neutral detergent fiber contents increased through phenological development. Crude protein ranged from 16.7 to 5.0%. In Vitro dry matter digestibility ranged from 84.8% to 57.0%. Mineral nutrients P, K, CA, Mg, Mn, Fe, Cu, Zn, and Na were analyzed and determined to be adequate for maintenance needs of ewes. / Graduation date: 2002

Coreplication experiments have revealed that replication of turnip yellow mosaic virus (TYMV) RNA in turnip protoplasts is cis-preferential. Genomes encoding mutant p141 or p66, proteins essential for virus replication, were inefficiently rescued by a helper genome. One model for the cis-preferential replication of TYMV is that p66 and p141 form a complex that associates with the RNA from which they are translated, limiting their availability in trans. Three types of experiments were used in this study in an attempt to obtain physical evidence for the hypothetical interaction between p66 and p141. Immunoprecipitations from in vitro translation reactions using antiserum that recognizes p66 (and its progenitor, p206) coprecipitate p141, indicating that the proteins form a complex in vitro. The results of coimmunoprecipitations of translation products with in-frame deletions did not lead to definitive information about interaction domains. p66 and the helicase domain of p141 do not detectably interact in the yeast two-hybrid system or in GST fusion interaction assays. Problems with the expression of full length p141 fusions make conclusions about the interaction of other p141 domains with p66 not possible at this time. Since the helicase domain of p141 does not appear to interact with p66, future experiments will focus on obtaining expression of smaller domains of p141, outside the helicase domain, and determining if they interact with p66. Variations to the model that do not necessitate the direct interaction between p66 and p141 are also considered. / Graduation date: 1997

Diverse sociology theoretical constructs serve as the lens to examine the evolution of two popular symbols of US culture in the last 20 years: yellow ribbons displayed as decoration and awareness ribbons worn as personal accoutrement. This research was motivated by society's weakened state of "collective consciousness," whereby shared beliefs and values have declined and some have completely disappeared, and sought to determine whether symbols will survive in a culture without commitment to the social. Invoking Christopher Lasch's Culture of Narcissism, Jean Baudrillard's Simulacra and Simulation, David Riesman's theory of other-directedness from The Lonely Crowd, and Stjepan Mestrovic's Postemotional Society, this work examined the significance of public displays of ribbons (whether on animate or inanimate objects), theorized why certain diseases and social causes "earned" their awareness ribbons and others did not, and demonstrated that these ribbons have served as multivalent symbols to accommodate our culture in a postmodern world. These symbols have not maintained their unifying function and now serve at the whim of the individual participant or observer. Ultimately, the act of wearing or displaying awareness ribbons and yellow ribbons, like so many other symbols, has been severed from the idea and is a freefloating, simulacrum to be used in whatever mode our postmodern, postemotional society requires.

The aim of this work was to understand the molecular mechanism of translation and the mechanism of translation termination, in particular. Cleavage of peptidyl-tRNA and peptide release terminates translation of mRNA on the ribosome. In prokaryotes, three release factors (RFs) are involved in this process. RF1 and RF2 recognise the three stop codons on mRNA and induce hydrolysis of the ester bond in peptidyl-tRNA. RF3 accelerates the rate of RF1 and RF2 recycling between ribosome in a GTP-dependent manner. We have clarified the mechanism of action of peptide release factor RF3. In the cell, free RF3 is in the GDP conformation. When RF3∙GDP binds to ribosome in complex with RF1 or RF2, these ribosome complexes act as guanine exchange factors for RF3 by inducing rapid dissociation of GDP. If, and only if, the peptide has been removed from tRNA, GDP is quickly replaced by GTP. Binding of GTP to RF3 induces a conformation of the factor with high affinity for the ribosome, which forces RF1 or RF2 to rapidly dissociate. Subsequent hydrolysis of GTP on RF3 induces a factor conformation with low affinity for the ribosome and rapid release of RF3∙GDP. It was further shown how the position of peptidyl-tRNA on the ribosome and the presence or absence of its peptide regulates the binding and GTPase activity of translation factors IF2, EF-G and EF-Tu. The result explains how idling GTPase hydrolysis and negative interference between different translation factors are minimized in living cells. The present biochemical observations, in conjunction with cryo-EM results, lead to new proposals for the role of hybrid sites in translocation of tRNAs, recycling of RF1 and RF2 by RF3 and recycling of post-termination ribosomes back to a new round of initiation.

Association mapping (AM), based on linkage disequilibrium, is a complementary strategy to traditional quantitative trait loci (QTL) mapping for describing associations between genotypes and phenotypes in crop plants. Yellow endosperm colour, an important quality trait in durum wheat (<i>Triticum turgidum L. var. durum</i>), was studied to determine the potential of AM to (1) identify previously reported QTL using a genome wide scan and (2) to determine allelic association of the phytoene synthase 1 (Psy1) gene using a candidate gene analysis. At present, a number of QTL for endosperm colour have been identified, and phytoene synthase, the initial enzyme of the carotenoid biosynthetic pathway, has been associated with QTL on the group 7 chromosomes which are considered to play a significant role in expression of yellow pigment concentration. CIE 1976 b*, a light reflectance measurement, and water-saturated butanol extracted pigments were assessed on a collection of 93 elite accessions from a variety of geographic origins, and genotyped with 245 markers. Population structure was assessed using genetic distance and Bayesian model based approaches, identifying five sub-populations consistent with breeding origin and pedigree. Association analysis identified significant associations with yellow endosperm colour on all chromosomes, including several previously identified QTL as well as new regions for genomic dissection. Pairwise LD mapping of Psy1-B1 and Psy1-A1 located the genes to chromosomes 7B and 7A respectively, to regions which have previously been identified for yellow pigment concentration QTL. The results of this study indicate that AM can be used to complement traditional QTL mapping techniques, and identify novel QTL for further study.

Yellow pigment (YP) concentration is an important quality trait in durum wheat (<i>Triticum turgidum</i> L. var <i>durum</i>) and is comprised primarily of carotenoids. The main objective of our study was to measure the accumulation of carotenoids during the grain fill period to improve our understanding of the physiological basis for differences among durum wheat cultivars. Thirteen cultivars and breeding genotypes with large variation in total YP concentration (<6 µg g-1 to >15 µg g-1) were studied. Spikes were sampled from replicated field plots in 2007 and 2008 near Saskatoon and Swift Current, Saskatchewan, Canada, at 14, 21, 28 and 35 days after heading (DAH). The remainder of each plot was combined at grain maturity for YP and carotenoid analysis. Carotenoids were extracted with 1:1 methanol:dichloromethane (0.1% BHT) and quantified with HPLC. <i>Trans</i> (E)-lutein was the predominant carotenoid at maturity and was detected at 14 DAH in all genotypes. The rate and duration of E-lutein accumulation was variable among genotypes expressing high, intermediate and low YP. The accumulation of all carotenoids was lowest in genotypes expressing low YP, and suggests rate limitations early in the carotenoid biosynthetic pathway. E-zeaxanthin concentrations were highest in mature grain, but no significant differences were detected among genotypes. However, the ratio of E-zeaxanthin to E-lutein was inversely correlated with total YP, suggesting that the â,å branch of lycopene cyclization is favoured over the â,â branch in high-YP genotypes. These results provide insights to the regulation of the carotenoid biosynthetic pathway during grain fill stage in durum wheat and will facilitate breeding for higher carotenoid concentration.

Association mapping (AM), based on linkage disequilibrium, is a complementary strategy to traditional quantitative trait loci (QTL) mapping for describing associations between genotypes and phenotypes in crop plants. Yellow endosperm colour, an important quality trait in durum wheat (<i>Triticum turgidum L. var. durum</i>), was studied to determine the potential of AM to (1) identify previously reported QTL using a genome wide scan and (2) to determine allelic association of the phytoene synthase 1 (Psy1) gene using a candidate gene analysis. At present, a number of QTL for endosperm colour have been identified, and phytoene synthase, the initial enzyme of the carotenoid biosynthetic pathway, has been associated with QTL on the group 7 chromosomes which are considered to play a significant role in expression of yellow pigment concentration. CIE 1976 b*, a light reflectance measurement, and water-saturated butanol extracted pigments were assessed on a collection of 93 elite accessions from a variety of geographic origins, and genotyped with 245 markers. Population structure was assessed using genetic distance and Bayesian model based approaches, identifying five sub-populations consistent with breeding origin and pedigree. Association analysis identified significant associations with yellow endosperm colour on all chromosomes, including several previously identified QTL as well as new regions for genomic dissection. Pairwise LD mapping of Psy1-B1 and Psy1-A1 located the genes to chromosomes 7B and 7A respectively, to regions which have previously been identified for yellow pigment concentration QTL. The results of this study indicate that AM can be used to complement traditional QTL mapping techniques, and identify novel QTL for further study.