Plant Science 156 (2000) 119 – 120
Book review
www.elsevier.com/locate/plantsci
Regulation of Primary Metabolic Pathways in Plants, Edited by N.J. Kruger S.A. Hill and R.G. Ratcliffe, Kluwer Academic Publishers, Dordrecht/
Boston/London, 1999. ISBN 0-7923-5494-X; US$. 180
This multi-authored book contains the proceed-ings of a congress of the Phytochemical Society of Europe (Oxford, January 1997) on the regulation of plant metabolism. The basic idea of the orga-nizers was not to give a broad account of the theme, but rather, through some generally well selected examples, to illustrate how metabolism is getting new interest with the recent developments of molecular techniques. The reader is progres-sively taken from studies at structural level of enzymes to the integration of pathways in the different cell compartments, tissues and organs, and finally to the use of trangenic plants as a means to modulate individual enzymes, highlight regulatory processes and hopefully to improve productivity.
The book, contains 14 articles covering some important aspects of the regulation of carbohy-drate production and utilisation. Chapters 1 and 2 report progress towards genetic engineering of Ru-bisco, for which the 3D-structure is known, to increase the specificity factor thus improving the carboxylation efficiency of the enzyme, and the molecular modelling of the active site of alterna-tive oxydase to clarify its predicted role as a di-oxygen scavenger. In Chapter 3, the authors summarize their results about the location, func-tional and regulatory properties (mainly regula-tory phosphorylation) of the multi-faceted PEP carboxykinase. Although this enzyme deserves in-terest as some of its physiological roles remain elusive, at least one among other well developped examples of post-translational modification of en-zymes should have been included to show how this
modulation impact on the regulation of
metabolism. One-carbon metabolic pathway is presented in detail, emphasizing the central role and fate of folate; it constitutes an excellent and comprehensive review on the topic (Chapter 4). Studies on the compartmentation of metabolites and metabolic pathways (starch, amino acids, lipids) and some of the corresponding transporters of photosynthetic and non-photosynthetic plastids envelopes, as well as metabolite distribution in different parts of the plant are described by lead-ing groups on these domains (Chapters 5 – 8). We realize that we know very little about the ex-tremely high complexity of interactions and coor-dination of metabolic pathway and the plasticity of plant metabolism. Based on the use of mutant and transgenic plants, new information is provided in Chapter 9 about the synthesis and organisation of amylose and amylopectin of starch granules. Again, the emerging idea is that there is no simple scheme that can be generalized as there are large variations in the way that starch-storing organs accumulate starch. How fructan metabolism is regulated in relation with the pivotal role of su-crose is the subject of Chapter 10. Transgenic technologies have been used successfully to modify and clarify further fructan metabolism (overex-pression of fructostyltransferase genes) with rea-sonable hopes to exploit fructans in the food and non-food industry. The situation is more complex in plants manipulated for sink metabolism empha-sizing the fact that much remains to be learnt about interactions between metabolism and gene expression before a clearcut interpretation can be proposed (Chapter 12). The concept that the metabolic control of flux is shared by several enzymes of a pathway is now based on a wealth of experimental data; Chapter 13 develops this sub-ject and stresses the fact that overexpressing the activity of a single enzyme in the pathway in order to increase the flux is useless in most cases. The message is clear, new perceptions of metabolic
Book re6iew 120
control have to be clarified before the application of laborious and time-consuming transgenic tech-nologies can be achieved to reach the objective. Finally, Chapter 14 excellently demonstrates that transgenic plants (plants under expressing nitrate reductase) are very useful to investigate how C/N metabolism is regulated and coordinated by ni-trate acting as a signal metabolite at the level of gene expression.
Albeit the book is published quite a long time after the meeting, most of the information and the discussions are still of great value for plant biolo-gists interested in the various topics included. One main merit of the book is that it underlines the point that metabolism is a dynamic process, with
intricate networks of pathways whose functioning and integration are highly regulated and, contrary to a pernicious way of thinking, is certainly far from being well understood, particularly as far as improvement of plant of agronomical importance is concerned. Investigations are still needed before well adapted strategies can be proposed to achieve this goal.
Jean Vidal
Institut de Biotechnologie des Plantes,
Bat. 630, 91405 Orsay,
Cedex,
France
E-mail: jean.vidal@ibp.u-psud.fr
