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Dissecting the plant cellular program for arbuscule development during AM symbiosis

Auditorium A134, Agricultural Technology Building
2014/03/07 3:00 PM
Dr. Maria J. Harrison (William H. Crocker Professor, Boyce Thompson Institute for Plant Research & Adjunct Professor, Department of Plant Pathology and Plant-Microbe Biology, Cornell University, USA)
Host: Tzyy-Jen Chiou
In natural ecosystems, most vascular flowering plants live in symbiosis with arbuscular mycorrhizal (AM) fungi. These mutually beneficial associations develop in the roots, where the fungus colonizes the cortex to obtain carbon from the plant. In addition to inhabiting the root, the fungus establishes hyphal networks in the soil, via which phosphorus and other mineral nutrients are transferred to the root. Thus, the symbiosis has a beneficial impact on plant health. Development of the AM symbiosis involves complex differentiation of both symbionts to create a symbiotic state. The fungus colonizes the cortical cells where it differentiates to create highly branched hyphae called arbuscules. As each arbuscule develops, the cortical cell surrounds the hyphal branches in a novel membrane, the periarbuscular membrane. The resulting arbuscule-cortical cell interface is the site of phosphate transfer to the plant cell.
Our research focuses on the molecular events that underlie development of the symbiosis with a particular emphasis on the arbuscule/cortical cell interface where symbiotic nutrient transfer occurs. A combination of genomics coupled with reverse genetics has enabled us to identify several components of the plant cellular program required for arbuscule development including DELLA proteins (Floss et al., 2013) and vapyrin (Pumplin et al., 2010), and also proteins required for maintenance of the symbiosis (Javot et al., 2007; Pumplin et al., 2012). Recent developments in these areas will be discussed.


Identification and characterization of a strigolactone transporter

Auditorium A134, Agricultural Technology Building
2014/03/07 4:00 PM
Dr. Enrico Martinoia (Professor Molecular Plant Physiology, Institute of Plant Biology, University of Zurich, Switzerland)
Host: Tzyy-Jen Chiou
In natural ecosystems, most vascular flowering plants live in symbiosis with arbuscular mycorrhizal (AM) fungi. These mutually beneficial associations develop in the roots, where the fungus colonizes the cortex to obtain carbon from the plant. In addition to inhabiting the root, the fungus establishes hyphal networks in the soil, via which phosphorus and other mineral nutrients are transferred to the root. Thus, the symbiosis has a beneficial impact on plant health. Development of the AM symbiosis involves complex differentiation of both symbionts to create a symbiotic state. The fungus colonizes the cortical cells where it differentiates to create highly branched hyphae called arbuscules. As each arbuscule develops, the cortical cell surrounds the hyphal branches in a novel membrane, the periarbuscular membrane. The resulting arbuscule-cortical cell interface is the site of phosphate transfer to the plant cell.
Our research focuses on the molecular events that underlie development of the symbiosis with a particular emphasis on the arbuscule/cortical cell interface where symbiotic nutrient transfer occurs. A combination of genomics coupled with reverse genetics has enabled us to identify several components of the plant cellular program required for arbuscule development including DELLA proteins (Floss et al., 2013) and vapyrin (Pumplin et al., 2010), and also proteins required for maintenance of the symbiosis (Javot et al., 2007; Pumplin et al., 2012). Recent developments in these areas will be discussed.


Live imaging of inorganic phosphate with cellular and subcellular resolution

Auditorium A134, Agricultural Technology Building
2014/03/10 10:30 AM
Dr. Wayne Versaw (Associate Professor , Department of Biology, Texas A&M University, USA)
Host: Tzyy-Jen Chiou
Inorganic phosphate (Pi) is an essential nutrient present in every compartment of a eukaryotic cell and serves key roles in energy conversion, signal transduction and the synthesis of a wide range of metabolites and macromolecules. Even modest changes in Pi distribution and cellular concentrations can dramatically influence growth and metabolism. To monitor such changes in plants and animals, and to understand how these are modulated in response to changes in environmental conditions and metabolic demands, we have developed an optimized series of fluorescence indicator protein for Pi (FLIPPi) FRET-based Pi sensors. Live imaging of these sensors expressed in Arabidopsis revealed dynamic control of cytosolic Pi in response to varied Pi supply and the direction of Pi transport mediated by a transporter located in plastids. Live Pi imaging in the nematode C. elegans suggests functional conservation of mechanisms for Pi mobilization in plants and animals.


TBA

Auditorium A134, Agricultural Technology Building
2014/03/31 10:30 AM
Dr. Jan van der Greef (Professor /Faculty of Science, Leiden Academic Centre for Drug Research, Analytical BioSciences, Universiteit Leiden, Netherlands)
Host: Ning-Sun Yang
The shift from a reductionistic towards a systems view is a key topic in Life Sciences.
System-based approaches need the understanding of the interconnectivity of systems and the organizing principles. Moreover, it requires a shift from disease management to the domain of health promotion. The latter is becoming a major focus as health care cost rise to a level that cannot be paid by society anymore and aiming at prevention becomes essential.
In order to achieve preventive strategies new insights need to be gathered on the concept of health and the measures of health. Moreover, the diagnostic principles need to be further refined and needs to address the personalized aspect. In Chinese medicine a holistic and personalized approach is key for both diagnosis and intervention for diseases or support of health and this creates a perfect match with Systems Science acting as a bridge between Western and Chinese medicine at the biochemical level.


Metabolism and Cancer Therapeutics: Targeting Arginine Addiction of Cancers

Auditorium A134, Agricultural Technology Building
2014/04/14 10:30 AM
Dr. Hsing-Jien Kung (President and Distinguished Investigator, National Health Research Institutes, Taiwan)
Host: Ning-Sun Yang
There is considerable evidence that tumor and normal cells differ in their metabolic requirements. The most prominent examples are the addiction of tumor cells to glucose (i.e., Warburg effect) and to glutamine. Therapeutics based on selective targeting of these metabolic pathways is under intensive investigations. Recently, we reported that irrespective of androgen receptor status, prostate cancer cells selectively and epigenetically suppress the expression of ASS (arginine succinosythethase), a rate-limiting enzyme for intracellular arginine synthesis. Analysis of over 100 PC specimens showed the complete absence of ASS expression, whereas some normal prostate epitheial cells express ASS. As a result, PC cells, but not normal counterparts become “auxotroph” for and addicted to external arginine. Thus, arginine-deprivation should selectively “starve” the PC cells to death. Indeed, in recent publications, we showed that depletion of external arginine by arginine deiminase (ADI) effectively induces cell death of CRPC cell lines, but not normal prostate epithelial cells in vitro and in vivo. In addition, we reported that ADI synergizes with Taxol in preclinical xenograft model. Based on this finding, a phaseI/II clinical trial is underway at UCD. Intriguingly, we found that ADI killing of cancer cells is associated with aggressive autophagy and appears to be caspase independent. At early phase, autophagy is protective and prolongs the survival of treated cells. Using high-resolution, live imaging, molecular and genetic profiling, we have now characterized in details the arginine-deprived cells undergoing apoptosis. The starved cells showed significant epigenetic reprogramming, excessive autophagy and most remarkably, nuclear rupture. The possible mechanism(s) and its implication will be discussed.


Achieving Food Security and Sustainability for 9.5 Billion

Auditorium A134, Agricultural Technology Building
2014/04/21 10:30 AM
Dr. Christopher J. Leaver (Emeritus Professor of Plant Science, Fellow of St John’s College, University of Oxford, UK)
Host: Ming-Che Shih
During the last 50 years the world population has more than doubled to more than 7 billion and is predicted to reach 9.5 billion by 2050. Eighty percent of this increase in population will live in the so called developing countries of China, India, Africa, SE Asia and South America, with the majority (more than 70%) living in an urban environment in megacities. Until recently the relative abundance of food has kept pace with global food production, with the poorest benefiting the most, yet almost 1 billion are malnourished and live below the poverty line. This dramatic increase in crop yields was due to a number of innovations: genetics and plant breeding (the so called ‘Green Revolution’), mechanisation, irrigation, NPK fertilisers and nitrogen in particular, and pesticides. Subsequently the developed world became complacent.
In order to feed this increase in population food production will have to rise by around 70 percent on essentially the same area of land. This will require ‘sustainable intensification - growing more from less’ by using land and resources more efficiently with the aim of meeting current needs while improving the ability of future generations to meet their own needs. In addition we must conserve natural resources and preserve ecosystem function while minimizing, adapting to and where possible, reversing the affects of climate change, decreased water availability, increased and changing biotic stress due to pests and pathogens, environmental pollution, loss of biodiversity and dietary upgrading.
To achieve this we must use all available technologies to select for, and modify, important agricultural and nutritional traits using marker-assisted plant breeding and genetic modification coupled with the appropriate use of agrochemical inputs (moving where possible from ‘chemical to biological solutions’) and sustainable farming practices. From my experience in Africa, where the population is predicted to double from 1 to 2 billion by 2050, I will argue that the world’s scientific community must be engaged in transferring the capacity for research and development leading to advances in agricultural productivity for the benefit of the poor in developing countries. These technologies must not only be applied to improving food production in major crops, but also in so called orphan crops which can address food security and nutrition as well as providing economic benefits to the famers Efforts should focus on access for poor, small scale farmers with particular attention to local needs and crop varieties and the capacity of each country to adapt its traditions and social heritage.While science can provide technological solutions, these have to be implemented in a responsible and fair way for them to have impact.This is not only the job of scientists but of politicians, policy makers, regulators and funding organizations. Now, and in the future, making sure everyone has enough to eat is more than ever about politics, socio-economics, communications and science -it is not just about ‘technology-fixes’.


Anticancer and Anti-inflammatory Activities of Korean Herbal Medicine

Auditorium A134, Agricultural Technology Building
2014/05/12 10:30 AM
Dr. Yeong Shik Kim (Professor College of Pharmacy Natural Products Research Institute Seoul National University Seoul, Korea)

Host: Ning-Sun Yang


竹子問題深入淺出

Conference Room A133, Agricultural Technology Building
2014/05/19 10:30 AM
呂錦明博士(前台灣省林業試驗所研究員;現任中華造林事業協會及台灣竹會顧問)
Host: Choun-Sea Lin


The role of ethylene, light signaling genes and priming in flooding tolerance

Auditorium A134, Agricultural Technology Building
2014/05/26 10:30 AM
Dr. Rens Voesenek (Head of Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, The Netherlands)
Host: Ming-Che Shih
The area exposed to flooding is on a world scale more than 17 million km2 per year; double the size of the USA. Due to global climate change the frequency and severity of floods will increase. These floods negatively interfere with plant life due to the obligate oxygen dependent life style of plants. When submerged, gas exchange between flooded plants and the atmosphere almost ceases and consequently plants are depleted in O2 and CO2. Naturally occurring flooding regimes have selected for two flood tolerance strategies in plants: (i) ’escape’ through vigorous shoot growth allowing snorkeling leaf tips to facilitate oxygen entry and diffusion to the anaerobic root tips, and (ii) ‘quiescence’ to endure long-term submergence by extremely slow rates of energy and carbohydrate consumption.
The wetland species Rumex palustris escapes from complete submergence by elongation of petioles. This submergence-induced response is regulated via an ethylene-driven signaling network. Genes, previously known from photomorphogenesis and shade avoidance, regulate under water elongation in a phytochrome independent manner. Work with R. palustris revealed a novel role for ethylene in ‘priming’ plants for subsequent anoxia. This is related to a much stronger expression of core-hypoxia responsive genes during anoxia in ethylene-pretreated plants. Priming in both Rumex and Arabidopsis will be discussed.


Flooding tolerance: exploiting natural variation in Arabidopsis.

Auditorium A134, Agricultural Technology Building
2014/05/26 2:30 PM
Dr. Rashmi Sasidharan (Assistant Professor, Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, The Netherlands)
Host: Ming-Che Shih


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