Phosphoenolpyruvate Carboxykinase Is Involved in the Decarboxylation of Aspartate in the Bundle Sheath of Maize

We recently showed that maize (Zea mays L.) leaves contain appreciable amounts of phosphoenolpyruvate carboxykinase (PEPCK; R.P. Walker, R.M. Acheson, L.I. Técsi, R.C. Leegood [1997] Aust J Plant Physiol 24: 459–468). In the present study, we investigated the role of PEPCK in C4 photosynthesis in maize. PEPCK activity and protein were enriched in extracts from bundle-sheath (BS) strands compared with whole-leaf extracts. Decarboxylation of [4-14C]aspartate (Asp) by BS strands was dependent on the presence of 2-oxoglutarate and Mn2+, was stimulated by ATP, was inhibited by the PEPCK-specific inhibitor 3-mercaptopicolinic acid, and was independent of illumination. The principal product of Asp metabolism was phosphoenolpyruvate, whereas pyruvate was a minor product. Decarboxylation of [4-14C]malate was stimulated severalfold by Asp and 3-phosphoglycerate, was only slightly reduced in the absence of Mn2+ or in the presence of 3-mercaptopicolinic acid, and was light dependent. Our data show that decarboxylation of Asp and malate in BS cells of maize occurs via two different pathways: Whereas malate is mainly decarboxylated by NADP-malic enzyme, decarboxylation of Asp is dependent on the activity of PEPCK

Judicial Perspectives of Domestic Violence Courts

The domestic violence court evolved with the feminist movement. As women gained rights, domestic violence became perceived as a male domination issue, rather than a private family matter. The development of the courts was based on therapeutic jurisprudence, and feminist and deterrence theory. Research regarding domestic violence courts is largely based on the effectiveness of victim advocates and batterer intervention programs. There is little to no research regarding judicial perspectives of the domestic violence court. Through inductive analysis of interviews and court observations, I examined how judges perceive the effectiveness of the courts and their general knowledge of domestic violence. Findings indicated that veteran judges and novice judges perceive their roles differently, and have different foci related to the execution of domestic violence hearings. Further, judges perceive victim advocates and lawyers as positive aspects of domestic violence courts, but find weaknesses related to the roles of law enforcement and prosecution. From these findings, I draw implications for judicial training as well as possibilities for a coordinated community response

Regulation of Leaf Senescence by Cytokinin, Sugars, and Light. Effects on NADH-Dependent Hydroxypyruvate Reductase

The aim of this study was to investigate the interactions between cytokinin, sugar repression, and light in the senescence-related decline in photosynthetic enzymes of leaves. In transgenic tobacco (Nicotiana tabacum) plants that induce the production of cytokinin in senescing tissue, the age-dependent decline in NADH-dependent hydroxypyruvate reductase (HPR), ribulose-1,5-bisphosphate carboxylase/oxygenase, and other enzymes involved in photosynthetic metabolism was delayed but not prevented. Glucose (Glc) and fructose contents increased with leaf age in wild-type tobacco and, to a greater extent, in transgenic tobacco. To study whether sugar accumulation in senescing leaves can counteract the effect of cytokinin on senescence, discs of wild-type leaves were incubated with Glc and cytokinin solutions. The photorespiratory enzyme HPR declined rapidly in the presence of 20 mM Glc, especially at very low photon flux density. Although HPR protein was increased in the presence of cytokinin, cytokinin did not prevent the Glc-dependent decline. Illumination at moderate photon flux density resulted in the rapid synthesis of HPR and partially prevented the negative effect of Glc. Similar results were obtained for the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. It is concluded that sugars, cytokinin, and light interact during senescence by influencing the decline in proteins involved in photosynthetic metabolism

Harnessing Saccharomyces cerevisiae Genetics for Cell Engineering

Cell engineering holds the promise of creating designer microorganisms that can address some of society's most pressing needs, ranging from the production of biofuels and drugs to the detection of disease states or environmental contaminants. Realizing these goals will require the extensive reengineering of cells, which will be a formidable task due both to our incomplete understanding of the cell at the systems level and to the technical difficulty of manipulating the genome on a large scale. In Chapter 1, we begin by discussing the potential of directed evolution approaches to overcome the challenges of cell engineering. We then cover the methodologies that are emerging to adapt the mutagenesis and selection steps of directed evolution for in vivo, multi-component systems. Yeast hybrid assays provide versatile systems for coupling a function of interest to a high-throughput growth selection for directed evolution. In Chapter 2, we develop an experimental framework to characterize and optimize the performance of yeast two- and three-hybrid growth selections. Using the LEU2 reporter gene as a model selectable marker, we show that quantitative characterization of these assay systems allows us to identify key junctures for optimization. In Chapter 3, we apply the same systematic characterization to the yeast three-hybrid counter selection, beginning with our previously reported URA3 reporter. We further develop a screening approach to identify effective new yeast three-hybrid counter selection reporters. Installing customized multi-gene pathways in the cell is arguably the first step of any cell engineering endeavor. Chapter 4 describes the design, construction, and initial validation of Reiterative Recombination, a robust in vivo DNA assembly method relying on homing endonuclease-stimulated homologous recombination. Reiterative Recombination elongates constructs of interest in a stepwise manner by employing pairs of alternating, orthogonal endonucleases and selectable markers. We anticipate that Reiterative Recombination will be a valuable tool for a variety of cell engineering endeavors because it is both highly efficient and technically straightforward. As an initial application, we illustrate Reiterative Recombination's utility in the area of metabolic engineering in Chapter 5. Specifically, we demonstrate that we can build functional biosynthetic pathways and generate large libraries of pathways in vivo. The facility of pathway construction by Reiterative Recombination should expedite strain optimization for metabolic engineering

Limitation of grassland productivity by low temperature and seasonality of growth

The productivity of temperate grassland is limited by the response of plants to low temperature, affecting winter persistence and seasonal growth rates. During the winter, the growth of perennial grasses is restricted by a combination of low temperature and the lack of available light, but during early spring low ground temperature is the main limiting factor. Once temperature increases, growth is stimulated, resulting in a peak in growth in spring before growth rates decline later in the season. Growth is not primarily limited by the ability to photosynthesize, but controlled by active regulatory processes that, e.g., enable plants to restrict growth and conserve resources for cold acclimation and winter survival. An insufficient ability to cold acclimate can affect winter persistence, thereby also reducing grassland productivity. While some mechanistic knowledge is available that explains how low temperature limits plant growth, the seasonal mechanisms that promote growth in response to increasing spring temperatures but restrict growth later in the season are only partially understood. Here, we assess the available knowledge of the physiological and signaling processes that determine growth, including hormonal effects, on cellular growth and on carbohydrate metabolism. Using data for grass growth in Ireland, we identify environmental factors that limit growth at different times of the year. Ideas are proposed how developmental factors, e.g., epigenetic changes, can lead to seasonality of the growth response to temperature. We also discuss perspectives for modeling grass growth and breeding to improve grassland productivity in a changing climate

The Pricing of Dutch Auction Rate Preferred Stock

Daniel T. Winkler is an Assistant Professor of Finance in thc Joseph M. Bryan School of Business and Economics, Department of Finance at The University of North Carolina at Greensboro and Tony R. Wingler is an Associate Professor of Finance in the Joseph M. Bryan School of Business and Economics, Department of Finance at The University of North Carolina at Greensboro

Theoretical study of nuclear spin polarization and depolarization in self-assembled quantum dots

We investigate how the strain-induced nuclear quadrupole interaction influences the degree of nuclear spin polarization in self-assembled quantum dots. Our calculation shows that the achievable nuclear spin polarization in In_{x}Ga_{1-x}As quantum dots is related to the concentration of indium and the resulting strain distribution in the dots. The interplay between the nuclear quadrupole interaction and Zeeman splitting leads to interesting features in the magnetic field dependence of the nuclear spin polarization. Our results are in qualitative agreement with measured nuclear spin polarization by various experimental groups.Comment: 14 pages, 13 figures, submitted to Physical Review

Comparison of signaling interactions determining annual and perennial plant growth in response to low temperature.

Low temperature inhibits plant growth despite the fact that considerable rates of photosynthetic activity can be maintained. Instead of lower rates of photosynthesis, active inhibition of cell division and expansion is primarily responsible for reduced growth. This results in sink limitation and enables plants to accumulate carbohydrates that act as compatible solutes or are stored throughout the winter to enable re-growth in spring. Regulation of growth in response to temperature therefore requires coordination with carbon metabolism, e.g., via the signaling metabolite trehalose-6-phosphate. The phytohormones gibberellin (GA) and jasmonate (JA) play an important role in regulating growth in response to temperature. Growth restriction at low temperature is mainly mediated by DELLA proteins, whose degradation is promoted by GA. For annual plants, it has been shown that the GA/DELLA pathway interacts with JA signaling and C-repeat binding factor dependent cold acclimation, but these interactions have not been explored in detail for perennials. Growth regulation in response to seasonal factors is, however, particularly important in perennials, especially at high latitudes. In autumn, growth cessation in trees is caused by shortening of the daylength in interaction with phytohormone signaling. In perennial grasses seasonal differences in the sensitivity to GA may enable enhanced growth in spring. This review provides an overview of the signaling interactions that determine plant growth at low temperature and highlights gaps in our knowledge, especially concerning the seasonality of signaling responses in perennial plants

INSTITUTO FEDERAL DE EDUCAÇÃO, CIÊNCIA E TECNOLOGIA: ANÁLISE DE PROCESSOS SOCIAIS DE EGRESSOS DO ENSINO SUPERIOR

Este estudo teve como principal objetivo analisar percursos desencadeados por alunos egressos do ensino superior, nas modalidades presencial e a distância, na figuração do Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo (Ifes) campus Cachoeiro de Itapemirim, para o qual se procedeu ao levantamento de informações referenciais, localização e necessidades do público egresso dessa figuração; à sistematização de dados relativos aos espaços profissionais e sociais ocupados pelos ex-alunos; à compreensão, por meio do discurso dos egressos, do seu percurso no ensino superior; à análise da percepção dos egressos acerca do currículo concluído, tendo por embasamento teórico a Sociologia Figuracional de Norbert Elias, apoiada nos conceitos de figuração, interdependência e processos sociais. Metodologicamente, recorreu-se ao estudo de caso como orientador do percurso do estudo e à utilização de estudo de documentos, questionário online com questões fechadas e abertas, entrevistas semiestruturadas e grupo focal como procedimentos para a coleta de dados. Os indicadores apurados com base nas respostas dos egressos viabilizaram a verificação dos objetivos estabelecidos no estudo, tais como: os egressos estão muito satisfeitos com o ensino recebido; sua maioria ocupa espaço de trabalho na área de formação nas redes pública (como servidor efetivo ou contratado) e na rede privada; a maioria é composta por trabalhadores ou participantes de algum programa vindo da assistência estudantil durante a realização do curso. A análise, a interpretação e a conclusão, ensejadas por uma diversificada coleta de dados, incluindo escuta direta dos egressos, representam importantes fontes de dados à instituição, no intuito de avaliar o ensino ofertado, saber se os egressos estão trabalhando em sua área de formação ou estão desempregados, se estão satisfeitos com os conteúdos adquiridos para o exercício da profissão e, sobretudo, se o Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo cumpre a sua missão de oferecer educação e produção de conhecimento socialmente válido para o mundo do trabalho, para a verticalização dos estudos e para o exercício da cidadania

Photorespiration: metabolic pathways and their role in stress protection

Photorespiration results from the oxygenase reaction catalysed by ribulose-1,5-bisphosphate carboxylase/ oxygenase. In this reaction glycollate-2-phosphate is produced and subsequently metabolized in the photorespiratory pathway to form the Calvin cycle intermediate glycerate-3-phosphate. During this metabolic process, CO2 and NH3 are produced and ATP and reducing equivalents are consumed, thus making photorespiration a wasteful process. However, precisely because of this ine¤ciency, photorespiration could serve as an energy sink preventing the overreduction of the photosynthetic electron transport chain and photoinhibition, especially under stress conditions that lead to reduced rates of photosynthetic CO2 assimilation. Furthermore, photorespiration provides metabolites for other metabolic processes, e.g. glycine for the synthesis of glutathione, which is also involved in stress protection. In this review, we describe the use of photorespiratory mutants to study the control and regulation of photorespiratory pathways. In addition, we discuss the possible role of photorespiration under stress conditions, such as drought, high salt concentrations and high light intensities encountered by alpine plants