Regulation of Primary Metabolic Pathways in Plants PDF
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REGULATION OF PRIMARY METABOLIC PATIIWAYS IN PLANTS Proceedings of the Phytochemical Society of Europe Volume 42 Regulation of Primary Metabolic Pathways in Plants Edited by Nicholas J. Kruger Steven A. Hin and R. George Ratcliffe Department of Plant Sciences, University of Oxford, Oxford, u.K. SPRINGER SCIENCE+BUSINESS MEDIA, B.V. A C.I.P. Catalogue record for Ihis book is available from the library of Congress. ISBN 978-94-010-6021-9 ISBN 978-94-011-4818-4 (eBook) DOI 10.1007/978-94-011-4818-4 P,inled on acid-fiu paper AII Righls Reserved (1 1999 Springer Science+Business Media Dordrecht Origina1ly published by Kluwer Academic Publishers in 1999 Softcovcr reprint ofthc hardcovcr Ist edition 1999 No pan of the material protected by Ihis copyright n()(ice may be reproduced or utilized in any form or by any means, electronic or mechanical, including pholocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner. This book is dedicated to the memory of Professor Tom ap Rees, outstanding researcher, inspirational teacher and tireless champion of plant science. TABLE OF CONTENTS Preface Nicholas 1. Kruger, Steven A. Hill and R. George Ratcliffe ix 1. Rubisco: attempts to reform a promiscuous enzyme Martin A. 1. Parry, Alfred 1. Keys, Graeme Bainbridge, Steven P. Colliver, P. John Andralojc, Matthew J. Paul, Fiona M. Banks and Pippa J. Madgwick 2. Insights into the active site of the plant alternative oxidase and its relationship to function Charles Affourtit and Anthony L. Moore 17 3. The many-faceted function of phosphoenolpyruvate carboxykinase in plants Richard C. Leegood, Richard M. Acheson, Laszlo I. Tecsi and Robert P. Walker 37 4. Folate synthesis and compartmentation in higher plants Fabrice Rebeille and Roland Douce 53 5. Structure and function of plastid metabolite transporters U1f-Ingo Fliigge, Andreas Weber, Birgit Kammerer, Rainer E. Hausler and Karsten Fischer 101 6. Integration of metabolism within non-photosynthetic plastids, and with the cytosol Mike 1. Emes, Ian 1. Tetlow and Caroline G. Bowsher 117 7. Carbon flux to fatty acids in plastids Stephen Rawsthorne, Fan Kang and Peter 1. Eastmond 137 8. Compartmentation of metabolites between the subcellular compartments of leaves, the apoplast, the phloem and the storage tissue of different crop plants Gertrud Lohaus, D Heineke, Anne Kruse, Kirsten Leidreiter, Burgi Riens, David G. Robinson, Heike Winter, Thilo Winzer and Hans W. Heldt 159 9. Regulation of starch synthesis in storage organs 173 Alison M. Smith 10. The integration of sucrose and fructan metabolism in temperate grasses and cereals Christopher J. Pollock, Andrew J. Cairns, Joseph Gallagher and Judith Harrison 195 11. Expression of fructosyltransferase genes in transgenic plants Irma Vijn, Anja van Dijken, Stefan Turk, Michel Ebskamp, Kees van Dun, Peter Weisbeck and Sjef Smeekens 227 12. The application of transgenic technology to the study of sink metabolism in potato . Richard N. Trethewey and Lothar WiIImitzer 239 13. Increasing the flux in a metabolic pathway: a metabolic control analysis perspective David A. Fell and Simon Thomas 257 14. Nitrate acts as a signal to control gene expression, metabolism and biomass allocation Mark Stitt and Wolf-Riidiger Scheible 275 Subject index 307 PREFACE Over the past decade, advances in molecular biology have provided the impetus for a resurgence of interest in plant metabolism. At a general level, the potential for modifying the quantity or quality of harvestable crop products through genetic manipulation has provided an agronomic rationale for seeking a greater understanding of primary plant metabolism and its regulation. Moreover, the now facile techniques for transformation of many plant species and the consequential capacity to manipulate the amounts of specific individual enzymes within specific cell types provides an exciting direct approach for studying metabolic problems. Such transgenic plants are also becoming invaluable tools in studies at the interface between metabolism and other sub-disciplines such as physiology and ecology. The interest generated in plant metabolism by these developments has also encouraged the re-introduction of more conventional biochemical techniques for metabolic analysis. Finally, in common with other areas of cell biology, the wealth of information that can be obtained at the nucleic acid level has provided the stimulus for identification and characterisation of metabolic processes in far greater detail than previously envisaged. The result of these advances it that researchers now have the confidence to address problems in plant metabolism at levels not previously attempted. This book presents the proceedings of an international conference held on 9-11 January 1997 at St Hugh's College, Oxford under the auspices of the Phytochemical Society of Europe. The aim of the meeting was to provide a timely review of progress in the area of primary plant metabolism, and in particular to highlight the extent to which molecular techniques now influence the investigation and understanding of plant metabolism. We deliberately chose to limit the scope of the meeting to the processes related to the dominant pathways of carbohydrate production and utilisation. This was done in the belief that it would enable topics to be considered in sufficient detail to identify the emerging themes and ideas in the field. The book is arranged to reflect the present focus on three broadly overlapping areas of investigation. It starts with a consideration of the structure of several enzymes of primary metabolism. A detailed understanding of metabolic regulation will ultimately require a description of the molecular interactions that modulate enzyme activity. Currently several hundred protein structures are determined each year, yet very few of these proteins are from plant sources. The opening chapters illustrate how a consideration of protein structure at different levels can enhance our understanding of the metabolic roles of specific enzymes, and may serve to stimulate further ix x interest in this approach. The second section of the book concentrates on integration of metabolism between organelles, cells, tissues and organs. Plant cells are both compartmented and differentiated. These features often define the unique organisation of metabolic processes and in turn determine the extent to which pathways and their intermediates may interact. The final section reviews attempts to define and manipulate some of the major pathways of carbohydrate metabolism, concluding with chapters considering theoretical difficulties associated with rational manipulation of metabolic flux, and the complex metabolic and developmental interactions that may arise as metabolism is perturbed. The material in this book illustrates three general themes that emerged during the meeting. The first is the extent to which molecular techniques are being integrated into plant biochemistry, and in particular the degree to which transgenic plants are now being used to address metabolic problems (rather than being paraded as a late 20th century form of Victorian freak show). The second is our increasing appreciation of the inherent heterogeneity of metabolism, and the current awareness of the compartmentation of metabolic processes at both the cellular and subcellular level. The third feature is the progress that is being made towards fulfilling the promise of manipulating metabolism for beneficial or profitable purposes. Nevertheless, we should not be too complacent about progress in this field. Although some of the changes that have been introduced in carbohydrate metabolism by genetic manipulation have been spectacular, in general they have resulted from conceptually simple alterations and have not been dependent on a profound understanding of regulation. Furthermore, as information accumulates, it is becoming increasingly apparent that metabolic processes vary between species (or even cell types). Thus, we cannot predict the precise pathways occurring in a particular tissue with any confidence. In addition, a common feature of plant metabolism is the degree to which individual enzyme activities or whole pathways are duplicated, often within different sub-cellular compartments. Such metabolic redundancy is often explained as a prerequisite for the flexibility needed by plants to regulate potentially conflicting pathways differentially in response to variable metabolic demands in a changing environment. Although this view is superficially attractive, we must be careful to guard against using it as a general explanation for the apparent duplication of metabolic processes, otherwise we will never seek a precise explanation for the function of individual isoforms, or the variable sub-cellular distribution of enzyme activities. As the results of the research described in this book illustrate, the task now facing researchers in this area is to understand the regulation xi of metabolism in specific cells within the context of the growth and development of the whole plant. We conclude on a note of sadness. The meeting was over-shadowed by the memory of the untimely death of- Professor Tom ap Rees a few months before the conference. Tom was an inspirational research scientist and teacher, who influenced the work and careers of many of those attending the meeting. In addition, he was scheduled to present the concluding talk at the meeting and had agreed to contribute to this book. Thus, in recognition of his contribution to the field of plant metabolism and in grateful thanks for his unique influence on the lives of two of the editors (NJK and SAH) we are honoured to be able to dedicate this book to the memory of Tom ap Rees. N.J. Kruger, S.A. Hill and R.G. Ratcliffe Department of Plant Sciences, University of Oxford Chapter 1 Rubisco: attempts to reform a promiscuous enzyme Martin A. J. Parry, Alfred J. Keys, Graeme Bainbridge, Steven P. Colliver, P. John Andralojc, Matthew J. Paul, Fiona M. Banks and Pippa J. Madgwick Biochemistry and Physiology Department, IACR-Rothamsted, Harpenden, Herts AL5 2JQ, UK Key words: ribulose bisphosphate carboxylase; Rubisco; specificity factor. Abstract: Despite its unique role in incorporating carbon from atmospheric CO2 into the organic substances of the biosphere, ribulose-I,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) is an inefficient enzyme; it has a low turnover number and catalyses several competing reactions, including oxygenation of ribulose-I,5-bisphosphate (ribulose-P2), in addition to the carboxylation of ribulose-P2. Information on the relative specificity for CO2 and O2 and the turnover number for mutant and native Rubisco from diverse species complements the increasing knowledge of the 3-dimensional structure of Rubisco at atomic resolution. We report progress towards improving the catalytic function by protein engineering and consider future experimental objectives. In particular. we have focused on loop 6 of the large subunit a//3 barrel domain and its interaction with the C-terminus of the large subunit. Rubisco is a target of great agronomic importance and genetic engineering offers the prospect of increased net carbon assimilation by increasing the specificity factor. Whilst the technologies are available to achieve this, additional mutants and 3- dimensional structures are needed to distinguish the structural and ionic components that determine specific catalytic properties of Rubisco. 1. INTRODUcnON Incorporation of carbon from atmospheric CO2 to organic carbon depends on the activity of ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco). Rubisco catalyses the carboxylation of N. J. Kruger et al. (eds.), Regulation ofP rimary Metabolic Pathways in Plants, 1-16. © 1999 Kluwer Academic Publishers.
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