The role of Arabidopsis transcription factors WRKY18 and WRKY40 in plant immunity

Two related Arabidopsis thaliana transcription factors, WRKY18 and WRKY40, are induced upon infection with the obligate biotrophic powdery mildew, Golovinomyces orontii (G. orontii), during early stages of infection. WRKY18 and WRKY40 negatively regulate host resistance as wrky18wrky40 double mutants are resistant towards this fungus. Differential expression of hormone biosynthesis and response genes between susceptible wildtype and resistant wrky18wrky40 plants suggested a crucial role of hormone signaling during G. orontii infection. Investigating the potential contribution of hormonal changes to resistance during this plant-pathogen-interaction is one focus of this thesis. Although hormone measurements did not reveal major differences between susceptible wildtype and resistant wrky18wrky40 plants, genetic studies demonstrated that SA biosynthesis is indispensable for resistance. Besides hormone-dependent defense responses, secondary metabolites, such as the indol-glucosinolate 4MI3G (4-Methoxyindol-3-ylmethylglucosinolat), have been shown to contribute to antifungal defense. Elevated levels of 4MI3G in infected wrky18wrky40 plants indicate a potential role of this compound in resistance towards G. orontii. Whereas WRKY18 and WRKY40 are negative regulators of resistance towards G. orontii, this was not the case for other powdery mildews. Hence, wrky18wrky40 mutants do not exhibit a broad-spectrum but rather specific resistance towards G. orontii infection. Furthermore, comprehensive wrky18wrky40 infection studies including different biotrophic, hemi-biotrophic and necrotrophic pathogens revealed a positive role of WRKY18 and WRKY40 in effector-triggered resistance towards avirulent Pseudomonas syringae DC3000 expressing the AvrRPS4 effector gene. This response appears to be highly specific since it was not observed with bacteria expressing other tested Avr genes. To further dissect roles of WRKY18 and WRKY40 in plant immunity and to uncover potential direct target genes of these transcription factors, global expression analyses of wrky18 and wrky40 single mutants upon G. orontii were performed. Overall, WRKY18 and WRKY40 function partly redundantly, but regulate highly diverse sets of genes. Direct binding of potential direct target genes will be analyzed by ChIP-PCR employing the newly generated WRKY18-HA complementation line. First results demonstrated WRKY18 feedback regulation on its own gene and the WRKY40 gene during G. orontii infection. In addition, a yeast 2-hybrid screen against a pathogen-induced cDNA-library revealed potential interaction partners of WRKY18 and WRKY40 that co-localize to the plant cell nucleus. In conclusion, this thesis contributes to further understanding the roles of WRKY18 and WRKY40 in plant immunity

2008 Progress Report on Brain Research

Highlights new research on various disorders, nervous system injuries, neuroethics, neuroimmunology, pain, sense and body function, stem cells and neurogenesis, and thought and memory. Includes essays on arts and cognition and on deep brain stimulation

Excellentia Eminentia Effectio

"In these pages you will learn about the fascinating research endeavors that each of our faculty members is undertaking. We have divided their research into the broad categories of health, sustainability, information, and systems. While we recognize the imperfect nature of categorizing research that, by its very nature may be interdisciplinary or transdisciplinary, we nonetheless believe it will be helpful as a way to see the depth and breadth of our research endeavors within each grouping. As you read the profiles on these pages, I know you will begin to appreciate that, taken as a whole, the research spectrum at Columbia Engineering is exceptional and that, as our professors go about their work, they are at the cusp of making breakthroughs that will have a major impact on the way we live our lives today and tomorrow.

Biotrophic Development of Ustilago maydis and the Response of Its Host Plant Maize

Fungal plant pathogens affect the quality of food and feed produced from infected plants and cause substantial yield losses every year. Especially fungi infecting cereal crops represent an ernormous thread. The biotrophic fungus Ustilago maydis is the causative agent of the smut disease on maize. Molecular pathways essential for the initiation of fungal pathogenicity, like mating of two compatible sporidia, the establishment of an infectious dikaryon and the penetration process leading to plant infection are intensively studied in U. maydis. However, the strategies used by the fungus to proliferate within the plant and to deal with the hostile environment, are vastly unknown. This dissertation investigates the complex molecular interplay between Ustilago maydis and its host plant in more detail, focusing on three different aspects. In U. maydis the initiation of sexual development and pathogenicity is controlled by two homedomain proteins bE and bW, which form an active transcription factor after fusion of two compatible sporidia. By constructing temperature-sensitive bE proteins, I was able to demonstrate that also the proliferation of U. maydis within the plant is regulated by the b mating type transcription factor (2.1). The inactivation of the bW/bE complex within the plant stops fungal development and leads to the deregulation of secreted proteins, which are believed to interfere with plant defense responses. U. maydis establishes a compatible biotrophic relationship with its host. To analyze the plant cell responses towards this forced interaction, global expression analysis and metabolic profiling were performed monitoring a time-course of infection (2.2). Expression analyses revealed an initial recognition of U. maydis by the maize plant, leading to the induction of basal plant defense responses. After U. maydis has penetrated the plant these defense responses are suppressed, suggesting an active interference with the plant immune system. Moreover, during disease progression U. maydis infected maize leaves do not develop into photosynthetically active source tissues, but maintain the characteristics of a nutrient sink. Like typical plant nutrient sinks the infected area is supplied with sucrose that is feeding the fungus. As nutrient availability determines the fitness of the pathogen, it also determines the pathogens success to conquer the plant. Thus, biotrophic fungi like U. maydis have to develop strategies to feed on nutrients provided by a living host plant. By identifying two U. maydis sugar transporters, Srt1 and Hxt1, as necessary for full fungal virulence, I was able to analyze which plant-derived carbohydrates are crucial for biotrophic development (2.3; 2.4). Srt1, a novel kind of sucrose transporter, is exclusively expressed during infection. Its unusual high sucrose affinity is well suited to compete with plant-derived sucrose uptake systems at the plant/fungus interfacen (2.3). Hxt1 utilizes hexoses glucose, fructose and mannose, and with lower affinity also galactose and xylose. Deletion of hxt1 reduces fungal pathogenicity, influences growth and hampers monosaccharide-dependent gene regulation. Moreover, expression analysis revealed that Hxt1 has a dual function as monosaccharide-transporter and -sensor (2.4). As double-deletion mutants of hxt1 and srt1 fail to induce severe disease symptoms, both uptake of sucrose and its cleavage products glucose and fructose are crucial for in planta development of U. maydis (2.4). U. maydis is recognized by the maize plant already prior to infection, resulting in the induction of basal plant defense responses. However, as soon as the fungus penetrates the plant these defense responses are manipulated by U. maydis, most probably caused by the action of fungal secreted proteins interfering with recognition and defense pathways. During disease progression, the infected maize tissue remains a sucrose-dependent nutrient sink, which lacks photosynthetic activity. This sink supplies U. maydis with sucrose and hexoses utilized by Srt1 and Hxt1 to promote fungal growth. Initiation and maintenance of the biotrophic interaction, including the expression of secreted proteins necessary to manipulate the host, are regulated by a complex transcription cascade, which is controlled by the bE/bW heterodimer. The b-cascade not only regulates fungal proliferation and differentiation, but also adapts the fungal needs towards changing plant tissues

Innovative miniaturized electroanalytical approaches for the analysis of clinically relevant glycoproteins

El objetivo principal de esta Tesis Doctoral ha sido el desarrollo de nuevas herramientas y estrategias electroquímicas (ultra)-miniaturizadas (sensores serigrafiados y sistemas microfluídicos), combinadas con nanomateriales como transductores electroquímicos, para la determinación de biomarcadores glicoproteicos de gran relevancia en el diagnóstico de enfermedades. En el contexto del diagnóstico clínico actual, existe una tendencia hacia el diseño y desarrollo de dispositivos portátiles que permitan el análisis descentralizado de los laboratorios clínicos, y que puede quedar englobada bajo el término POCT (de sus siglas en inglés Point-of-Care Testing). Este término describe aquellas pruebas o ensayos que se realizan en lo que podría denominarse en el punto de necesidad (cerca o por el propio del paciente, incluso de forma remota). Además de los desarrollos propios de la electrónica, el desarrollo y éxito de la tecnología POCT ha dependido y depende en gran medida del diseño y desarrollo de nuevas tecnologías analíticas (ultra)-miniaturizadas. Los dispositivos basados en la transducción electroquímica han resultado ser esenciales en el desarrollo de (bio)-sensores, produciendo plataformas simples, pero precisas y sensibles, para el diagnóstico de enfermedades y ha sido uno de los enfoques más prometedores para el desarrollo de POCTs, debido en general a su instrumentación económica y a su fácil miniaturización. Esta Tesis Doctoral aborda el análisis de dos glicoproteínas: la alfa-1-ácido glicoproteína (AGP) y la transferrina (Tf). La primera se utiliza como biomarcador glicoproteico de procesos inflamatorios, y la segunda como biomarcador de una enfermedad rara denominada trastornos congénitos de la glicosilación (CDG). La detección electroquímica puede ser una buena alternativa para la determinación de glicoproteínas debido a su miniaturización inherente, sus elevadas sensibilidad y selectividad y su bajo coste. Sin embargo, la oxidación directa de las glicoproteínas presenta baja sensibilidad debido a que los carbohidratos presentes en las mismas son electroquímicamente inactivos en condiciones cercanas a las fisiológicas. Para paliar este inconveniente, se ha propuesto el uso de complejos de osmio (VI) con ligandos nitrogenados [Os (VI) L] como sonda electroquímica. El complejo de osmio (VI) reacciona con los grupos diol de los carbohidratos formándose un éster de osmato que produce dos señales electroquímicas en electrodos de carbono. El objetivo de la Tesis Doctoral ha sido el diseño y desarrollo de dos tipos de herramientas analíticas (ultra)-miniaturizadas compatibles con la tecnología POCT, sensores y sistemas microfluídicos electroquímicos, para el análisis de las glicoproteínas seleccionadas, AGP y Tf. En efecto, de forma específica se proponen, de forma evolutiva en lo que a las prestaciones analíticas requeridas por un POCT electroquímico se refiere: i) sensores electroquímicos serigrafiados basados en carbono y en carbono nanoestructurado para el análisis individual de las glicoproteínas, ii) microchip de electroforesis capilar para el análisis simultáneo de ambas y, iii) nuevos dispositivos microfluídicos desechables de flujo pasivo y con capacidad de integración de las etapas analíticas para la determinación individual de las glicoproteínas. Las herramientas electroquímicas desarrolladas han permitido no sólo la determinación rápida, fiable, in situ y con bajo coste de estos biomarcadores relevantes en el diagnóstico clínico de importantes enfermedades, sino un avance conceptual hacia la descentralización del análisis clínico y, por ende, una mejora del diagnóstico actua

Transhumanism and Society: The Social Debate Over Human Enhancement

This book provides an introductory overview to the social debate over enhancement technologies with an overview of the transhumanists\u27 call to bypass human nature and conservationists\u27 argument in defense of it. The author present this controversy as it unfolds in the contest between transhumanists proponents and conservationists, who push back with an argument to conserve human nature and to ban enhancement technologies. Readers are informed about the discussion over humanism, the tension between science and religion, and the interpretation of socio-technological revolutions; and are invited to make up their own mind about one of the most challenging topics concerning the social and ethical implications of technological advancements

Mining a Small Medical Data Set by Integrating the Decision Tree and t-test

[[abstract]]Although several researchers have used statistical methods to prove that aspiration followed by the injection of 95% ethanol left in situ (retention) is an effective treatment for ovarian endometriomas, very few discuss the different conditions that could generate different recovery rates for the patients. Therefore, this study adopts the statistical method and decision tree techniques together to analyze the postoperative status of ovarian endometriosis patients under different conditions. Since our collected data set is small, containing only 212 records, we use all of these data as the training data. Therefore, instead of using a resultant tree to generate rules directly, we use the value of each node as a cut point to generate all possible rules from the tree first. Then, using t-test, we verify the rules to discover some useful description rules after all possible rules from the tree have been generated. Experimental results show that our approach can find some new interesting knowledge about recurrent ovarian endometriomas under different conditions.[[journaltype]]國外[[incitationindex]]EI[[booktype]]紙本[[countrycodes]]FI