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The biosynthesis and metabolism of plant hormones
90
T I B S - February 1985
Hot w o r k o n plant hormone The Biosynthesis and Metabolism of Plant H o r m o n e s edited by Alan Crozier and John R. Hillman, Cambridge University Press, 1984. £17.50 (xii + 288 pages) 1SBN 0 521 26424 3 The publication of this seminar series volume will be welcomed gratefully by those of us who attended the Society for Experimental Biology Conference where the papers which comprise this book were read. This is because the talks took place during a heat-wave and it became nearly impossible to concentrate as the temperature in the lecture theatres climbed (in the absence of airconditioning) into the mid-30s centigrade. In any case, plant physiologists are not conditioned to absorb subtle differences between complex structural formulae; many gave up the unequal struggle and decided to wait for the publication of the proceedings. However, this small subsection of the potential readership will not be alone in eagerly awaiting the volume: the subject matter is so potentially confusing that a clear exposition has been needed for some time. In addition, the superb selection of experts assembled by the editors and the level at which this series is pitched (bridging the gap between out-of-date general texts and over-specialized research papers) will ensure popularity, as will the fair price. Ever since the hormone concept was first used to describe the control by endogenous chemicals of growth and development phenomena in plants, there has been argument about the exact role and nomenclature of the compounds involved. Are they really hormones, according to Starling's original definition? Does the specialized nature of physiological control required in the Plant Kingdom mean that the analogy with the mammalian system is irrelevant or even misleading? Or is the comparison with animals a useful one whose value has been obscured by difficulties with the experimental systems and the use of methods which yielded ambiguous results? Much of this discussion has, unfortunately, been conducted in the absence of reliable information. The study of the biosynthesis and metabolism of plant hormones is especially important in this context because it is tied so closely to their modes of action, This is well illustrated in the case of the gibberellins, a group of closely-related terpenoid compounds, many of which
biochemist~
have profound effects on growth and development. Over 50 members of this group have been characterized and knowledge about their relationships in metabolic pathways has revealed that only a few may be truly active molecules. The others, whilst apparently active in bioassays, are actually transformed after application and before response to one or other of these active compounds. Moreover, the information obtained in this type of biochemical study has useful commercial application quite apart from the diffuse benefits of a greater understanding of plant life; for instance, the stimulatory effects of two specific gibberellins on tree flowering have been used to speed up conifer breeding programmes by tens of years per generation, It must be emphasized how difficult it is to obtain reliable data about plant hormones and their metabolites. They are present in extremely small amounts against a background of many secondary products and extensive purification and reliable identification are prerequisites for their accurate quantification. It is
encouraging to see in this hook the progress being made now that methods such as high-pressure liquid chromatography (HPLC) followed by immunoassay or mass spectrometry are routinely applied. Especially where the workers involved are general physiologists turned biochemists, rather than the converse, these data are related in a commendable fashion to physiological phenomena and experimental or 'genetic' treatments. The high overall standard of the book reflects the excellent choice of experts made by the editors: in nearly all cases they are truly the leaders in their fields and in these days of over-publication this can rarely be said of any multiple-author work. I found that the typewriter-based typeface took a little getting used to, but this was more than made up for by the incorpotation of an index (missing in earlier volumes in the series). Yes, a book worth sweating for, and a must for anyone with a research or advanced teaching interest in plant hormones. JONATHAN D. B. WEYERS Departmentof Biological Sciences, Universi~of Dundee,Dundee DD 4HN, UK.
WeD-trodden areas of muscle research Muscle and Non-muscle Motility. Vol. 1 edited by Alfred Stracher, Academic Press, 1983. $45.00 (xi + 372 pages) ISBN 0 12 673001 6 When Thompson and Wolpert showed in 1963 that contractility in extracts of amoebae was associated with filaments, the search for muscle proteins in nonmuscle cells was on. As the details of non-muscle contractile systems emerge it is clear that, although they contain some of the muscle proteins, they work rather differently. Motile cells do not have little muscles and are not even always contractile. However where actin and myosin occur together it is likely that their interaction produces tension by the sliding filament principle, This book, the first in the series, is mainly about muscle with some asides about non-muscle cells. There is an extremely clear account by H. E. Huxley of the experimental basis of the sliding filament theory, from the early evidence of X-ray diffraction and electron microscopy to thecurrent picture of moving crossbridges obtained from synchrotron radiation. The sliding filament theory leads to some interesting speculations about gross physiology; though if
animals of similar construction have similar top speeds regardless of their size, why cannot a small child keep up with an adult? More is known about the assembly of filaments of actin than myosin and this is evident from the chapters on the two proteins. The description of myosin filament assembly might have been more palatable if some theoretical aspects had been included; for example, determination of the amino acid sequence of myosin has prompted speculation about the association of molecules and it would have been interesting to hear how this tallies with the various models proposed. In contrast, progress in the physical chemistry of actin has been almost too fast for muscle biologists. Over twenty years ago Oosawa and his colleagues proposed the helical polymerization theory for the transformation of G-actin monomers into filamentous F-actin. Only in the last few years has it been recognized how important the processes are for understanding the G to F transformation and its control in non-muscle cells. In pioneering experiments in 1953, Tsao showed that the actin monomer had considerable mobility in the filament and that bound myosin increased
T I B S - February 1985
Hot w o r k o n plant hormone The Biosynthesis and Metabolism of Plant H o r m o n e s edited by Alan Crozier and John R. Hillman, Cambridge University Press, 1984. £17.50 (xii + 288 pages) 1SBN 0 521 26424 3 The publication of this seminar series volume will be welcomed gratefully by those of us who attended the Society for Experimental Biology Conference where the papers which comprise this book were read. This is because the talks took place during a heat-wave and it became nearly impossible to concentrate as the temperature in the lecture theatres climbed (in the absence of airconditioning) into the mid-30s centigrade. In any case, plant physiologists are not conditioned to absorb subtle differences between complex structural formulae; many gave up the unequal struggle and decided to wait for the publication of the proceedings. However, this small subsection of the potential readership will not be alone in eagerly awaiting the volume: the subject matter is so potentially confusing that a clear exposition has been needed for some time. In addition, the superb selection of experts assembled by the editors and the level at which this series is pitched (bridging the gap between out-of-date general texts and over-specialized research papers) will ensure popularity, as will the fair price. Ever since the hormone concept was first used to describe the control by endogenous chemicals of growth and development phenomena in plants, there has been argument about the exact role and nomenclature of the compounds involved. Are they really hormones, according to Starling's original definition? Does the specialized nature of physiological control required in the Plant Kingdom mean that the analogy with the mammalian system is irrelevant or even misleading? Or is the comparison with animals a useful one whose value has been obscured by difficulties with the experimental systems and the use of methods which yielded ambiguous results? Much of this discussion has, unfortunately, been conducted in the absence of reliable information. The study of the biosynthesis and metabolism of plant hormones is especially important in this context because it is tied so closely to their modes of action, This is well illustrated in the case of the gibberellins, a group of closely-related terpenoid compounds, many of which
biochemist~
have profound effects on growth and development. Over 50 members of this group have been characterized and knowledge about their relationships in metabolic pathways has revealed that only a few may be truly active molecules. The others, whilst apparently active in bioassays, are actually transformed after application and before response to one or other of these active compounds. Moreover, the information obtained in this type of biochemical study has useful commercial application quite apart from the diffuse benefits of a greater understanding of plant life; for instance, the stimulatory effects of two specific gibberellins on tree flowering have been used to speed up conifer breeding programmes by tens of years per generation, It must be emphasized how difficult it is to obtain reliable data about plant hormones and their metabolites. They are present in extremely small amounts against a background of many secondary products and extensive purification and reliable identification are prerequisites for their accurate quantification. It is
encouraging to see in this hook the progress being made now that methods such as high-pressure liquid chromatography (HPLC) followed by immunoassay or mass spectrometry are routinely applied. Especially where the workers involved are general physiologists turned biochemists, rather than the converse, these data are related in a commendable fashion to physiological phenomena and experimental or 'genetic' treatments. The high overall standard of the book reflects the excellent choice of experts made by the editors: in nearly all cases they are truly the leaders in their fields and in these days of over-publication this can rarely be said of any multiple-author work. I found that the typewriter-based typeface took a little getting used to, but this was more than made up for by the incorpotation of an index (missing in earlier volumes in the series). Yes, a book worth sweating for, and a must for anyone with a research or advanced teaching interest in plant hormones. JONATHAN D. B. WEYERS Departmentof Biological Sciences, Universi~of Dundee,Dundee DD 4HN, UK.
WeD-trodden areas of muscle research Muscle and Non-muscle Motility. Vol. 1 edited by Alfred Stracher, Academic Press, 1983. $45.00 (xi + 372 pages) ISBN 0 12 673001 6 When Thompson and Wolpert showed in 1963 that contractility in extracts of amoebae was associated with filaments, the search for muscle proteins in nonmuscle cells was on. As the details of non-muscle contractile systems emerge it is clear that, although they contain some of the muscle proteins, they work rather differently. Motile cells do not have little muscles and are not even always contractile. However where actin and myosin occur together it is likely that their interaction produces tension by the sliding filament principle, This book, the first in the series, is mainly about muscle with some asides about non-muscle cells. There is an extremely clear account by H. E. Huxley of the experimental basis of the sliding filament theory, from the early evidence of X-ray diffraction and electron microscopy to thecurrent picture of moving crossbridges obtained from synchrotron radiation. The sliding filament theory leads to some interesting speculations about gross physiology; though if
animals of similar construction have similar top speeds regardless of their size, why cannot a small child keep up with an adult? More is known about the assembly of filaments of actin than myosin and this is evident from the chapters on the two proteins. The description of myosin filament assembly might have been more palatable if some theoretical aspects had been included; for example, determination of the amino acid sequence of myosin has prompted speculation about the association of molecules and it would have been interesting to hear how this tallies with the various models proposed. In contrast, progress in the physical chemistry of actin has been almost too fast for muscle biologists. Over twenty years ago Oosawa and his colleagues proposed the helical polymerization theory for the transformation of G-actin monomers into filamentous F-actin. Only in the last few years has it been recognized how important the processes are for understanding the G to F transformation and its control in non-muscle cells. In pioneering experiments in 1953, Tsao showed that the actin monomer had considerable mobility in the filament and that bound myosin increased