Peter Nick (Ed.) • Plant Microtubules Potential for Biotechnology Springer-Verlag Berlin Heidelberg GmbH Peter Nick (Ed.) Plant Microtubules Potential for Biotechnology With 38 Figures 'Springer Dr. Peter Nick Institute for Biology II University of Freiburg SchănzlestraBe 1 79104 Freiburg Germany ISBN 978-3-662-22302-4 Library of Congress Cataloging-in-Publication Data Plant microtubules: potential for biotechnology 1 Peter Nick (ed.). P.cm Includes bibliographical references. ISBN 978-3-662-22302-4 ISBN 978-3-662-22300-0 (eBook) DOI 10.1007/978-3-662-22300-0 1. Plant microtubules. 2. Plant cell biotechnology. 1. Nick, Peter,l962- QK725 .P5655 2000 571.6'542--dc21 This work is subject to copyright. Ali rights reserved, whether the whole or part of the material is concer ned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, repro duction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9,1965, in its cur rent version, and permission for use must always be obtained from Springer-Verlag Berlin Heidelberg GmbH. Violations are liable for prosecution under the German Copyright Law. o Springer-Verlag Berlin Heidelberg 2000 Originally published by Springer-Verlag Berlin Heidelberg New York in 2000 Softcover reprint of the hardcover 1s t edition 2000 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: E. Kirchner, Heidelberg Typesetting: Camera ready by P. Nick SPIN 10707141 31/3136-5 4 3 2 1 O-Printed on acid-free paper Preface Manipulation of plant architecture is regarded as a new and promising issue in plant biotechnology. Given the important role of the cytoskeleton during plant growth and development, microtubules provide an important target for biotech nological applications aiming to change plant architecture. The scope of this book is to introduce some microtubule-mediated key processes that are important for plant life and amenable to manipulation by either genetic, pharmacological or ecophysiological rationales. The first part of the book deals with the role of mi crotubules for plant morphogenesis. Microtubules control plant shape at three levels: 1. Control of cell expansion: cortical microtubules define the orientation of newly synthetized cellulose microfibrils and thus the mechanical anisotropy of the cell wall. Transverse microtubules are a prerequisite for stable cell elongation, whereas oblique or longitudinal microtubules favour a shift in the growth axis towards lateral growth. 2. Control of cell division: the microtubular preprophase band defines axis and symmetry of the ensuing cell division. It marks the site where, after completion of chromosome segregation, the new cell plate will be laid down. This is the cellular basis for the control of branching patterns and phyllotaxis. 3. Control of cell-wall structure: cortical microtubules are bundled at those sites, where cell-wall thickenings are going to be formed. The orientation of cortical microtubules will therefore define the direction of these cell-wall thickenings and thus the spatial framework for lignification. This influences the mechanical prop erties of wood. The second part of the book covers the role of microtubules in response to en vironmental factors. The focus is on three aspects Of this vast field: 4. Control of the response to biotic stress: microtubules seem to be involved in the migration of the nucleus towards the infected site upon pathogen attack. The spread of plant viruses such as the tobacco mosaic virus between cells of infected plants seems to utilize actin microfilaments and microtubules. Reorientation of microtubules that are aligned over several cells accompanies wound healing and the establishment of new vessel contacts. Formation ofmycorhiza and Rhizobium induced root-nodules are further topics in this context. 5. Control of the response to metals: metal ions, such as aluminum or cadmium, limit crop yields in about 40% of the world's arable lands. They cause swelling of root cells and a loss of cell axis. For aluminum, a direct interaction with tubulin VI Preface dynamics has been discovered, opening the possibility to analyze and control the cytoskeletal response to this metal. 6. Control of the response to low temperature: microtubules depolymerize in re sponse to chilling. In plants, the cold sensitivity of microtubules is well correlated with the chilling tolerance of the whole plant. It is possible to manipulate the cold sensitivity of microtubules by ecophysiological rationales and/or certain growth regulators. Moreover, various tubulin isotypes seem to exist that differ in cold sensitivity. The third part of the book deals with the tools that can be used for biotechno logical manipulation: 7. Tubulin genes: in all plant species tested so far there exist several tubulin genes corresponding to several tubulin isotypes with subtle differences in charge, tissue expression, temporal expression and signal inducibility. The corresponding tubu lin isotypes seem to confer altered responses of microtubules to cold, herbicides and hormones. These isotypes could either be used directly to manipulate the behaviour of microtubules and thus the response of the plant to stress, or on the other hand, the promotors for these genes could be utilized to drive the expression of other genes of interest with a specific, possibly inducible, spatiotemporal pat tern of expression. 8. Cytoskeletal mutants: an increasing panel of mutants becomes available that has been selected either for altered resistance to cytoskeletal drugs or for a changed pattern of morphogenesis. 9. Cytoskeletal drugs: several herbicides act either directly on microtubule assem bly or indirectly on microtubule dynamics by interfering with signal chains that control microtubule dynamics. In addition, several growth regulators exert their effect via the microtubular cytoskeleton. There exist species and cultivar differ ences in drug sensitivity that could be used for weed control as well as for the control of crop growth. The scope of the book is twofold: it gives a comprehensive overview of the numerous functions of microtubules during different aspects of plant life, and it proposes to make use of the potential of microtubules to influence fundamental aspects of plant life such different as height and shape control, mechanical prop erties of wood or resistance to pathogens or abiotic stress. Freiburg, Germany, March 2000 Peter Nick Contents 1 Control of Plant Height..................................................... 1 Peter Nick 2 Control ofPlant Shape....................................................... 25 Peter Nick 3 Control of Wood Structure................................................ 51 RyoFunada 4 Control of the Response to Biotic Stresses....................... 83 Issei Kobayashi and Yuhko Kobayashi 5 Control of the Response to Aluminum Stress.................. 103 Mayandi Sivaguru, Hideaki Matsumoto and Walter J. Horst 6 Control of the Response to Low Temperature................. 121 Peter Nick 7 Tubulin Genes and Promotors.......................................... 13 7 Diego Breviario 8 Microtubular and Cytoskeletal Mutants........................... 159 Vance Baird, Yaroslaw B. Blume, and Susan M. Wick 9 Anticytoskeletal Herbicides............................................... 193 Kevin C. Vaughn Subject Index.................................................................... 207 1 Control of Plant Height Peter Nick lnstitut fiir Biologie II, Schanzlestr. I, D-791 04 Freiburg, Germany 1.1 Summary Control of plant height is important for agriculture, because plant height deter mines the mechanical stability of many crop plants. Resistance to wind, logging resistance, efficiency of light usage, microclimate, but also the partitioning of biomass from vegetative to reproductive structures are traits that depend directly or indirectly on plant height. In most cases, a reduction in plant height is the de sired trait. However, conventional agriculture that is characterized by high density and high nutrient supply tends to create an environment enhancing plant height, and thus reducing plant stability (e.g. increased internode length caused by the shade avoidance response). On the cellular level, these responses are based primarily on increased cell elongation. The repartitioning of cell expansion from longitudinal towards lateral expansion requires manipulation of the reinforcement mechanism that controls cell axiality. The orientation of cellulose microfibrils plays a pivotal role in this process. The deposition of cellulose and thus the axiality of the cell are controlled by cortical microtubules. The current state of the microtubule-microfibril syn drome will be briefly reviewed at this point (physical contact versus membrane channels). In the next step, the research on microtubule reorientation triggered by environmental signals will be presented with a special focus on those factors that are likely to be involved in the field (shade avoidance, phytochrome, gibberel lins). The chapter will continue with the biochemical knowledge that has been accumulated so far about the mechanism of microtubule reorientation. In the final part, potential applications will be given: manipulation of microtubule dynamics by transgenic approaches, by application of certain chemicals, and by ecophysi ological rationals. 1.2 Significance of the problem for agriculture Control of plant height has been a major topic in agriculture for several decades, especially in graminean crops, such as wheat, rice, barley, rye and oats (Luib and Schott 1990; Bomer et al. 1996). In wheat and barley, the resistance of a plant to lodging and windbreak has been found to be inversely related to plant height (Oda et al. 1966): 2 Control of plant height W·M with w=fresh weight, M=bending momentum at breaking, l=culm height and w=dry weight of the culm per tiller. Thus, lodging resistance will increase parabolically with decreasing plant height. The agricultural losses caused by lodging are enormous: up to 10-50% in wheat (Laude and Pauli 1956; Weibel and Pendleton 1961), up to 60% in barley (Schott and Lang 1977; Knittel et al. 1983), and 20-40% in rice (Basak 1962; Kwon and Yim 1986; Nishiyama 1986). In addition, the quality of the grains in terms of mal ting quality, baking quality or carbohydrate content are negatively affected by lodging (Andersen 1979). Moreover, the costs for harvest and grain drying may increase by 50% (Luib and Schott 1990). Lodging occurs mainly in two forms, as so-called root lodging, a bending of the culms just above the surface (Pinthus 1973), or as so-called stem lodging at higher internodes after heading. Approaches to improve lodging resistance in graminean crops have focussed either on the introduction of dwarfing genes by conventional breeding (Borner et al. 1996; Makela et al. 1996; Mcleod and Payne 1996), or, alternatively, on the application of growth regulators such as chlorme quat chloride or ethephone (Schott and Lang 1977; Schreiner and Reed 1908; Tolbert 1960). Both approaches often act via the gibberellin pathway. The major ity of the known dwarfing genes are affecting either gibberellin biosynthesis (Phinney and Spray 1990; Borner et al. 1996) or the responsiveness to gibberel lins (Borner et al. 1996). The growth-retardant chlormequat interferes with gib berellin biosynthesis (Frost and West 1977) or utilization (Coolbaugh and Ham ilton 1976). Ethephon, on the other hand, acts by stimulating the release of en dogenous ethylene (Andersen 1979). These massive shifts in the hormonal balance, caused either genetically or by application of growth retardants, can have undesirable side effects, such as pre cocious flowering along with incomplete grain filling (Makela et al. 1996), in creased transpiration and reduced drought resistance (Kirkham 1983), reduced gametic viability (Dotlacil and Apltauerova 1978) or reduced root development (Luib and Schott 1990). In addition, only some crops are amenable to this strategy (Jung 1964; Clark and Fedak 1977): whereas wheat and rye respond very well, the success is less pronounced in species such as barley, maize or rice. Moreover, the success of growth retardants seems to be limited to root lodging, whereas chemi cal suppression of stem lodging bears increased risks for unfavourable side effects (Andersen 1979). Despite these serious drawbacks of chemical growth retardants, they have been used extensively - in 1989, for instance, 46% of wheat, and 18% of barley fields in Europe were treated with growth retardants (Luib and Schott 1990).