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演講訊息

Cytokinin-Induced Priming of the Plant Immune System

Auditorium A134, Agricultural Technology Building, Agricultural Biotechnology Research Center
2017/10/16 10:30 AM
Dr. Cris Argueso (Assistant Professor, Department of Bioagricultural Sciences and Pest Management, Colorado State University, USA)
Host: Cheng-Hsun Ho


Lipidomics sheds light on diabetic neuropathy

Auditorium A134, Agricultural Technology Building, Agricultural Biotechnology Research Center
2017/10/16 3:30 PM
Dr. Xianlin Han (Professor of Medicine and Biochemistry at the Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, USA)
Host: Yet-Ran Chen
Utilizing our enabling shotgun lipidomics technology platform, we have recently determined the changes of lipids in brain and nerve tissue samples from db/db mice in a spatiotemporal manner. We have revealed markedly reduction of myelin lipids in a gradient from sciatic nerve, then spinal cord, to brain cortex, occurred as early as one month of age when the blood glucose level of mice is still normal. We have expanded the findings from lipidomics studies on db/db mice to other diabetic mouse models, including ob/ob, high fat diet-induced and streptozotocin (STZ)-treated mice, and post-mortem brain tissues of diabetic patients. We have found that the losses of myelin lipids are present in all samples of type 2 diabetes mellitus (T2DM) models and patients, but not in T1DM mice (i.e., STZ-treated mice), indicating that the losses of myelin lipids are specific to T2DM. Physiological and electrophysiological studies have demonstrated the reduced levels of ATP in the nerve tissues and the aberrant nerve conduction, respectively, indicating the connection of myelin lipid losses with diabetic neuropathy in T2DM. Mechanistic studies have showed that the losses of myelin lipids are not due to alterations in gene expressions and/or protein activities, but due to the deficiency in carnitine content under the pathological conditions. Accordingly, lipidomics studies have not only identified the underlying molecular mechanism leading to diabetic neuropathy in T2DM, but also indicate the important roles of nutrients in health and disease.
Acknowledgements: This work was partly supported by National Institute of General Medical Sciences Grant R01 GM105724, American Diabetes Association, and intramural institutional research funds.


Advances in mass spectrometry for the identification of lipid isomers

Auditorium A134, Agricultural Technology Building, Agricultural Biotechnology Research Center
2017/10/16 2:00 PM
Dr. Stephen Blanksby (Director, Central Analytical Research Facility (CARF), Institute for Future Environments, Queensland University of Technology, Australia)
Host: Yet-Ran Chen
Advances in mass spectrometry have been a significant driver in the emerging field of lipidomics. Improvements in speed, sensitivity and mass accuracy of modern instrumentation, although largely developed for other fields (e.g., proteomics and metabolomics), have improved our ability to detect lipids at very low concentrations within complex extracts. Peculiar challenges arise however, in the structural characterisation of lipids that are not directly addressed by generic performance enhancements in contemporary mass spectrometers. In particular, the differentiation of isomeric lipids including, double bond-positional isomers, sn-positional isomers and stereoisomers (e.g., cis and trans double bonds). It is often difficult or even impossible to distinguish such isomers by conventional mass spectrometry approaches in a manner that is also compatible with the high through-put workflows demanded by many lipidomics applications. The lack of ready access to these critical molecular features is an impediment to our understanding of fundamental structure-function relationships in lipid biochemistry. Our group is attempting to address these challenges through the development and application of mass spectrometric technologies specifically targeting the separation and identification of isomeric lipids. In this presentation we demonstrate the capabilities of ozone-induced dissociation mass spectrometry - used either in isolation or in combination with collision-induced dissociation - to provide detailed structure elucidation of complex lipid ions in the gas phase. In addition, we combine these approaches with chromatography and ion-mobility spectrometries to facilitate the separation of isomeric lipids and thus relative quantitation of isomer populations. Examples from a number of biological extracts will be presented to highlight the rich variety of isomeric lipids in nature and thus provoke questions as to the reasons for such molecular diversity.


Functions of AMT-type membrane proteins in radial ammonium transport and in ammonium-dependent lateral root branching

Auditorium A134, Agricultural Technology Building, Agricultural Biotechnology Research Center
2017/10/23 10:30 AM
Prof. Dr. Nicolaus von Wirén (Professor for Plant Physiology and Cell Biology at the University of Halle and Head of the Department for Physiology & Cell Biology at IPK Gatersleben, Germany)
Host: Cheng-Hsun Ho
Ammonium is, besides nitrate, the most important N source for most plants. For efficient uptake of ammonium by roots, plants have evolved a set of AMT-type membrane proteins, which differ in biochemical transport properties and cell type-specific expression and thus take over different transport functions. To quantify the relative contribution of radial transport pathways, we dissected symplastic and apoplastic pathways for ammonium transport in Arabidopsis roots by expressing cell type-specific ammonium transporters (AMT) in a mutant with defective Casparian strips at the endodermis. Using 15N-labeled ammonium, we quantified for the first time radial transport rates for ammonium through the apoplastic and the symplastic transport pathway and identified synergistic and antagonistic interactions between these pathways and the apoplastic bypass.
In addition, AMT-dependent ammonium transport is also involved in modifications of the root system architecture, as local supply of ammonium supply increases lateral root density. To elucidate the mechanisms underlying the regulation of root architecture under local ammonium supply, we used pharmacological and genetic approaches and found that AMT- and ammonium-dependent lateral root branching strongly interferes with auxin transport and homeostasis.


  

2017 SEMINAR

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