- Email: [email protected]
An intricate, growing communication web
update 31 Grote, M. et al. (1995) Localizationofprofilin- and actin-like immunoreactivity in in vitro-germinated tobaccopollen tubes by electron microscopyafter special water-free fixation techniques, Sex. Plant Reprod. 8, 180-186 32 Dr~bak, B.K. et al. (1994) Inhibition of plant plasma membrane phosphoinositide phospholipase C by the actin-binding protein, profilin, Plant J. 6,389-400 33 Sohn, R.H. et al. (1995) Localizationof a binding site for phosphatidylinositol-4,5-bisphosphate on human profilin, J. Biol. Chem. 270, 21114-21120 34 Eberle, M. et al. (1990) Is there a relationship between phosphatidylinositol trisphosphate and F-actin polymerizationin human neutrophils? J. Biol. Chem. 265, 16725-16728 35 DrObak, B.K. (1996) Metabolism of plant phosphoinositides and other inositol-containing lipids, in Membranes: Specialized Functions in Plants (Smallwood,M., Knox, J.P. and Bowles, D.J., eds), pp. 195-214, Bios 36 Lu, P-J. et al. (1996) Lipid products of phosphoinositide 3-kinase bind human profilin with high affinity, Biochemistry 35, 14027-14034 37 Singh, S.S. et al. (1996) Profilin and gelsolin stimulate phosphatidylinositol 3-kinase activity, Biochemistry 35, 16544-16549
book review
An intricate, growing communication web Signal Transduction in Plants edited by P. Aducci
Birkh#.user, Molecular and Cell Biology Updates, 1997. DM108.00 (i + 161 pages) ISBN 3 7643 5307 4
//
The last decade has seen considerable progress in defining major elements of signal transduction pathways in plant cells. Combined approaches using cell physiology, biochemistry, molecular biology and
© 1997 ElsevierScience Ltd
38 Kim, S.R., Kim, Y. and An, G. (1993)Molecular cloningand characterization of anther-preferential cDNAencoding a putative actindepolymerizingfactor, Plant MoL Biol. 21, 39-45 39 Rozycka,M. et al. (1995) A Zea mays pollen cDNAencodinga putative actin-depolymerizingfactor, Plant Physiol. 107, 1011-1012 40 Lopez,I. et al. (1996)Pollen specificexpression of maize genes encoding actin depolymerizingfactor-like proteins, Proc. Natl. Acad. Sci. U. S. A. 93, 7415-7420 41 Hatanaka, H. et al. (1996) Tertiary structure of destria and structural similarity between two actin-regulating protein families, Cell 85, 1047-1055 42 Carlier, M.F. et al. (1997) Actin depolymerizingfactor (ADF/cofilin) enhances the rate of filament turnover: implication in actin-based motility, J. Cell Biol. 136, 1307-1322 Christopher Staiger,, Bryan Gibbon, David Kovar and Laura Zonia are at the Dept of Biotogica! Sciences I Purdue Universit'yl West
Lafayette, IN 47906-1392, USA. *Author for correspondence(tel ÷1 765 496 1769; fax + i 765 496 1496; e,mail cstaiger@bilbo:bio:purdue.edu).
genetics have revealed that plants share common elements with known signalling pathways in animal systems, and have also evolved their own specific pathways mixing prokaryotic and eukaryotic transduction repertoires. Signal Transduction in Plants provides an updated overview of this rapidly advancing field, illustrating through several examples how plants perceive biotic and abiotic signals and transduce them into biological responses. The book is multiauthored, and organized into three sections, corresponding to the major classes of signals that plants have to deal with: chemical signals, including hormones and phytotoxins; light, as a physical signal from the environment; and biotic signals, involved in the control of plant-microorganism interactions. The chapters on hormones describe what is known about abscisic acid, auxin and ethylene signalling. For these different hormones, parallel approaches using biochemistry and genetics have been used to try to find the identity of specific receptor(s) and elements of the transduction cascades; functional assays appear to be the necessary link for matching these approaches and relating them to plant physiology. A fruitful combination of research on the physiology of single cells, and both mutant and transgenic plants, has recently been achieved for the study of abscisic acid signalling in guard cells. Studies on guard cells have also highlighted the critical role of ion channels in initiating early events in abscisic acid transduction cascades, and also probably in mediating the responses of plant cells to
many physiological stimuli. Until now, only partial views of the complex network of hormone signalling cascades have emerged. As recently discussed for auxin 1, considering the number of steps involved in hormone signal transduction, more mutants might have been expected from the development of genetic analyses. This lack of mutants may be because of pleiotropy and redundancy of hormone effects, and highlights the need for further refinement of the selection screens used. This may also indicate that mutations in the genes encoding receptors or key transduction elements are lethal, and therefore never recovered, a problem that could be overcome by conditional mutants. Little is yet known about the mode of action of phytotoxins. Most nonhost-selecrive phytotoxins act on plasma membrane targets (e.g. H +- and CaU-ATPases, and Ca 2+ channels) but, except for fusicoccin, the mechanisms of their recognition are far from being identified. The fusicoccin receptor has been purified, and turned out to belong to the family of 14-3-3 proteins. On the basis of fusicoccin action on the plasma membrane H+*ATPase, the postulated role of this protein is the control of a kinasemediated reaction regulating the activity of this proton pump. Such mechanisms are likely to participate in other, as yet unknown, regulatory pathways 2, and future research will be dedicated to the identification of new 14-3-3 target proteins. Two chapters discuss recent progress in understanding the complexities of photoregulated processes mediated by different families of photoreceptors. The recent
July1997,Vol.2, No.7
281
update literature testifies to the rapid and dramatic progress in this area since the isolation of Arabidopsis mutants impaired in their capacity to respond to red or blue light. These genetic studies revealed that plants possess at least three different bluelight receptors and associated transduction systems, with little or no overlap. Individual phytochromes (responsive to red and far-red light) can now be assigned to particular responses, and some of the cotresponding transduction events are known. Here again, the next challenge to address is the overlap between biochemical approaches, which have allowed the definition of positive regulatory elements in the transduction pathways, and genetic models, from which most of the gene products identified probably correspond to repressots in the same pathways. The last chapter focuses on the perception of fungal elicitors and the mechanisms for transducing these signals into plant defence responses. Besides studies aimed at the purification of elicitor molecules, and attempts to clarify their transduction pathways, the recent cloning of resistance genes has shed light on the possible mechanisms of fungal elicitor recognition by the plant cell. From a more global point of view, the cloning of several classes of resistance genes involved in specific plant-pathogen interactions now allows us to address the crucial question as to whether different resistance gene products either activate distinct resistance mechanisms or converge into a few common pathways that coordinate the overall defence response 3. Each chapter in Signal Transduction in Plants constitutes a good source of references for researchers in the area and for a wider audience. Although this book does not provide a comprehensive description of the field (the most recent and exciting data on brassinosteroids4 and small peptides5, which uncover new transduction pathways in plants, are not included), it reflects the exponentially advancing progress towards the unravelling of plant signalling networks.
H~lbne Barbier-Brygoo Institut des Sciences Vegetales, Centre National de la Recherche Scientifique (CNRS), Unite Propre de Recherche 40, Avenue de la Terrasse, F-91198 Gif sur Yvette Cedex, France (tel +33 1 69 82 38 68; fax +33 1 69 82 37 68; e-mail [email protected])
References 1 Walden; R. and Lubenow, H. (1996) Genetic dissection of auxin action: more questions than answers? Trends Plant Sci. 10, 335-339 2 De Boer, B. (1997) Fusicoccin- a key to multiple 14-3-3 locks? Trends Plant Sci. 2, 60~6 282
July 1997,Vol.2, No.7
3 Hammond-Kosack,K.E. and Jones, J.D.G. (1996) Resistance gene-dependent plant defense responses, Plant Cell 8, 1773-1791 4 Clouse, S.D. (1996) Molecular genetic studies confirm the role of brassinosteroids in plant growth and development, Plant J. 10, 1-8 5 Miklashevichs, E. et al. (1996) Do peptides control plant growth and development? Trends Plant Sci. 1, 411
Fungus roots Mycorrhizal Symbiosis (2nd edn) by S.E. Smith and D.J. Read Academic Press, 1997. £65.00 hbk (ix + 605 pages) ISBN 0 12 652840 3
This edition of Mycorrhizal Symbiosis is the most complete single volume on the subject. In spite of the book being only marginally thicker than the previous edition 1, it is broader in scope, and still remains remarkably well balanced in its treatment of several important topics. As stated in the preface, the book has essentially been rewritten. Fortunately, as is appropriate in a book of this sort, the various sections still present a historical perspective, despite some intentional weeding out of older material. The authors have covered all the major topics that I would have included. The new material includes sections that deal with the following: molecular interactions between plants and fungi; the nitrogen nutrition of ectomycorrhizal plants; longdistance transport of materials through hyphae; the role played by mycorrhizal fungi in natural ecosystems; the relevance of mycorrhizas to field crops and forestry; and practical considerations, such as inoculure production. The book also emphasizes the importance of the mycelium in the soil, and variability in function among mycorrhizal fungus species.
The new chapter on the role of mycorrhizas in ecosystems is wonderfully integrative, and could have been used as the introduction to place in context the various mycorrhizal symbioses found in nature. The organization of the chapter by biome is a useful way of making sense of the vast diversity of mycorrhizal function. Excellent new chapters on agriculture (field crops and forestry) are also welcome additions. In fact, our appreciation that mycorrhizas are integral parts of natural ecosystems suggests that mycorrhizal fungi could be managed to great advantage in agricultural systems. I found this new edition to be both enjoyable to read and directly useful. In particular, the ability succinctly to capture the methodology and logic leading to the conclusions of the various key studies included is admirable. The list of references is also very comprehensive. Chapter conclusions, which were also included in the previous edition, continue to be useful as short syntheses, being neither too long to be repetitive, nor too short to be useless. Edited volumes, which are essentially compilations of independent chapters, certainly have their place in the literature. Yet in such works there can be little 'pulling together' of seemingly disparate parts. In contrast, Mycorrhizal Symbiosis has achieved a high level of integration, and this indicates a good appreciation of all the material by both authors. For example, the section on translocation in mycorrhizal fungi integrates information about both vesicular-arbuscular and ectomycorrhizal fungi. Ideally, an edited volume should reflect less bias than a two-authored volume. The authors here even caution us that the book reflects their biases. Either I share those biases, or the book is remarkably even handed! Indeed, there are several places where previous studies of the authors themselves have been critically reviewed. The photographs range from very good to excellent. In general, other figures are of high quality, particularly those that were redrawn or replotted for this volume. For a few, however, the ~eproduction was comparatively poor. The manual by Brundrett et al. 2 has uniformly excellent figures that were apparently either redrawn or made especially for that work. A similar undertaking for this book, although tremendously labor-intensive, would improve the presentation of information in some cases. I was surprised to note the intentional exclusion of the word 'infection', which, in my opinion, still correctly describes what a fungus does as it burrows through host tissue. The use of 'colonization' in place of
© 1997 ELsevierScience Ltd
book review
An intricate, growing communication web Signal Transduction in Plants edited by P. Aducci
Birkh#.user, Molecular and Cell Biology Updates, 1997. DM108.00 (i + 161 pages) ISBN 3 7643 5307 4
//
The last decade has seen considerable progress in defining major elements of signal transduction pathways in plant cells. Combined approaches using cell physiology, biochemistry, molecular biology and
© 1997 ElsevierScience Ltd
38 Kim, S.R., Kim, Y. and An, G. (1993)Molecular cloningand characterization of anther-preferential cDNAencoding a putative actindepolymerizingfactor, Plant MoL Biol. 21, 39-45 39 Rozycka,M. et al. (1995) A Zea mays pollen cDNAencodinga putative actin-depolymerizingfactor, Plant Physiol. 107, 1011-1012 40 Lopez,I. et al. (1996)Pollen specificexpression of maize genes encoding actin depolymerizingfactor-like proteins, Proc. Natl. Acad. Sci. U. S. A. 93, 7415-7420 41 Hatanaka, H. et al. (1996) Tertiary structure of destria and structural similarity between two actin-regulating protein families, Cell 85, 1047-1055 42 Carlier, M.F. et al. (1997) Actin depolymerizingfactor (ADF/cofilin) enhances the rate of filament turnover: implication in actin-based motility, J. Cell Biol. 136, 1307-1322 Christopher Staiger,, Bryan Gibbon, David Kovar and Laura Zonia are at the Dept of Biotogica! Sciences I Purdue Universit'yl West
Lafayette, IN 47906-1392, USA. *Author for correspondence(tel ÷1 765 496 1769; fax + i 765 496 1496; e,mail cstaiger@bilbo:bio:purdue.edu).
genetics have revealed that plants share common elements with known signalling pathways in animal systems, and have also evolved their own specific pathways mixing prokaryotic and eukaryotic transduction repertoires. Signal Transduction in Plants provides an updated overview of this rapidly advancing field, illustrating through several examples how plants perceive biotic and abiotic signals and transduce them into biological responses. The book is multiauthored, and organized into three sections, corresponding to the major classes of signals that plants have to deal with: chemical signals, including hormones and phytotoxins; light, as a physical signal from the environment; and biotic signals, involved in the control of plant-microorganism interactions. The chapters on hormones describe what is known about abscisic acid, auxin and ethylene signalling. For these different hormones, parallel approaches using biochemistry and genetics have been used to try to find the identity of specific receptor(s) and elements of the transduction cascades; functional assays appear to be the necessary link for matching these approaches and relating them to plant physiology. A fruitful combination of research on the physiology of single cells, and both mutant and transgenic plants, has recently been achieved for the study of abscisic acid signalling in guard cells. Studies on guard cells have also highlighted the critical role of ion channels in initiating early events in abscisic acid transduction cascades, and also probably in mediating the responses of plant cells to
many physiological stimuli. Until now, only partial views of the complex network of hormone signalling cascades have emerged. As recently discussed for auxin 1, considering the number of steps involved in hormone signal transduction, more mutants might have been expected from the development of genetic analyses. This lack of mutants may be because of pleiotropy and redundancy of hormone effects, and highlights the need for further refinement of the selection screens used. This may also indicate that mutations in the genes encoding receptors or key transduction elements are lethal, and therefore never recovered, a problem that could be overcome by conditional mutants. Little is yet known about the mode of action of phytotoxins. Most nonhost-selecrive phytotoxins act on plasma membrane targets (e.g. H +- and CaU-ATPases, and Ca 2+ channels) but, except for fusicoccin, the mechanisms of their recognition are far from being identified. The fusicoccin receptor has been purified, and turned out to belong to the family of 14-3-3 proteins. On the basis of fusicoccin action on the plasma membrane H+*ATPase, the postulated role of this protein is the control of a kinasemediated reaction regulating the activity of this proton pump. Such mechanisms are likely to participate in other, as yet unknown, regulatory pathways 2, and future research will be dedicated to the identification of new 14-3-3 target proteins. Two chapters discuss recent progress in understanding the complexities of photoregulated processes mediated by different families of photoreceptors. The recent
July1997,Vol.2, No.7
281
update literature testifies to the rapid and dramatic progress in this area since the isolation of Arabidopsis mutants impaired in their capacity to respond to red or blue light. These genetic studies revealed that plants possess at least three different bluelight receptors and associated transduction systems, with little or no overlap. Individual phytochromes (responsive to red and far-red light) can now be assigned to particular responses, and some of the cotresponding transduction events are known. Here again, the next challenge to address is the overlap between biochemical approaches, which have allowed the definition of positive regulatory elements in the transduction pathways, and genetic models, from which most of the gene products identified probably correspond to repressots in the same pathways. The last chapter focuses on the perception of fungal elicitors and the mechanisms for transducing these signals into plant defence responses. Besides studies aimed at the purification of elicitor molecules, and attempts to clarify their transduction pathways, the recent cloning of resistance genes has shed light on the possible mechanisms of fungal elicitor recognition by the plant cell. From a more global point of view, the cloning of several classes of resistance genes involved in specific plant-pathogen interactions now allows us to address the crucial question as to whether different resistance gene products either activate distinct resistance mechanisms or converge into a few common pathways that coordinate the overall defence response 3. Each chapter in Signal Transduction in Plants constitutes a good source of references for researchers in the area and for a wider audience. Although this book does not provide a comprehensive description of the field (the most recent and exciting data on brassinosteroids4 and small peptides5, which uncover new transduction pathways in plants, are not included), it reflects the exponentially advancing progress towards the unravelling of plant signalling networks.
H~lbne Barbier-Brygoo Institut des Sciences Vegetales, Centre National de la Recherche Scientifique (CNRS), Unite Propre de Recherche 40, Avenue de la Terrasse, F-91198 Gif sur Yvette Cedex, France (tel +33 1 69 82 38 68; fax +33 1 69 82 37 68; e-mail [email protected])
References 1 Walden; R. and Lubenow, H. (1996) Genetic dissection of auxin action: more questions than answers? Trends Plant Sci. 10, 335-339 2 De Boer, B. (1997) Fusicoccin- a key to multiple 14-3-3 locks? Trends Plant Sci. 2, 60~6 282
July 1997,Vol.2, No.7
3 Hammond-Kosack,K.E. and Jones, J.D.G. (1996) Resistance gene-dependent plant defense responses, Plant Cell 8, 1773-1791 4 Clouse, S.D. (1996) Molecular genetic studies confirm the role of brassinosteroids in plant growth and development, Plant J. 10, 1-8 5 Miklashevichs, E. et al. (1996) Do peptides control plant growth and development? Trends Plant Sci. 1, 411
Fungus roots Mycorrhizal Symbiosis (2nd edn) by S.E. Smith and D.J. Read Academic Press, 1997. £65.00 hbk (ix + 605 pages) ISBN 0 12 652840 3
This edition of Mycorrhizal Symbiosis is the most complete single volume on the subject. In spite of the book being only marginally thicker than the previous edition 1, it is broader in scope, and still remains remarkably well balanced in its treatment of several important topics. As stated in the preface, the book has essentially been rewritten. Fortunately, as is appropriate in a book of this sort, the various sections still present a historical perspective, despite some intentional weeding out of older material. The authors have covered all the major topics that I would have included. The new material includes sections that deal with the following: molecular interactions between plants and fungi; the nitrogen nutrition of ectomycorrhizal plants; longdistance transport of materials through hyphae; the role played by mycorrhizal fungi in natural ecosystems; the relevance of mycorrhizas to field crops and forestry; and practical considerations, such as inoculure production. The book also emphasizes the importance of the mycelium in the soil, and variability in function among mycorrhizal fungus species.
The new chapter on the role of mycorrhizas in ecosystems is wonderfully integrative, and could have been used as the introduction to place in context the various mycorrhizal symbioses found in nature. The organization of the chapter by biome is a useful way of making sense of the vast diversity of mycorrhizal function. Excellent new chapters on agriculture (field crops and forestry) are also welcome additions. In fact, our appreciation that mycorrhizas are integral parts of natural ecosystems suggests that mycorrhizal fungi could be managed to great advantage in agricultural systems. I found this new edition to be both enjoyable to read and directly useful. In particular, the ability succinctly to capture the methodology and logic leading to the conclusions of the various key studies included is admirable. The list of references is also very comprehensive. Chapter conclusions, which were also included in the previous edition, continue to be useful as short syntheses, being neither too long to be repetitive, nor too short to be useless. Edited volumes, which are essentially compilations of independent chapters, certainly have their place in the literature. Yet in such works there can be little 'pulling together' of seemingly disparate parts. In contrast, Mycorrhizal Symbiosis has achieved a high level of integration, and this indicates a good appreciation of all the material by both authors. For example, the section on translocation in mycorrhizal fungi integrates information about both vesicular-arbuscular and ectomycorrhizal fungi. Ideally, an edited volume should reflect less bias than a two-authored volume. The authors here even caution us that the book reflects their biases. Either I share those biases, or the book is remarkably even handed! Indeed, there are several places where previous studies of the authors themselves have been critically reviewed. The photographs range from very good to excellent. In general, other figures are of high quality, particularly those that were redrawn or replotted for this volume. For a few, however, the ~eproduction was comparatively poor. The manual by Brundrett et al. 2 has uniformly excellent figures that were apparently either redrawn or made especially for that work. A similar undertaking for this book, although tremendously labor-intensive, would improve the presentation of information in some cases. I was surprised to note the intentional exclusion of the word 'infection', which, in my opinion, still correctly describes what a fungus does as it burrows through host tissue. The use of 'colonization' in place of
© 1997 ELsevierScience Ltd