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Microtubules as ‘green fingers’ for crop improvement
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Forum
TRENDS in Plant Science Vol.6 No.4 April 2001
Book Review
Microtubules as ‘green fingers’ for crop improvement Plant Microtubules. Potential for Biotechnology Edited by Peter Nick. Springer-Verlag, 2000. DM149.00/£51.50/US$110.00 hbk (vi + 209 pages) ISBN 3 540 67105 6
At the dawn of the third millennium, the survival of the world’s poorest people is at stake. The challenge is to find the cheapest appropriate answers to enhance food quality, quantity and access. Using genetic engineering, or the so-called ‘green’ biotechnology, scientists are in the process of creating safe tools to modify plant genomes. Their aim is to produce more crops by enhancing their resistance to pathogens and to stress, better crops by increasing their nutrient value, and cheaper crops by reducing the need for pesticides and herbicides without yield loss. Plants can also be used as vaccination vectors because edible vaccines are a convenient and inexpensive way of immunizing against infectious diseases. For example, vaccines against hepatitis have been developed in banana1 and vaccines against cholera in potato. Plant Microtubules. Potential for Biotechnology is written by 12 authors, and deals with the biological mechanisms implicating microtubules and the potential role of microtubules in new strategies to raise yield ceilings by changing plant architecture. Because the cytoskeleton is involved in key mechanisms of plant growth and development, microtubules are a useful target for genetic, pharmacological or ecophysiological manipulation. Tubulins are encoded by multigene families and are ubiquitous in eukaryotes. Plant microtubules appear to have more functions than their animal counterparts. Specialized microtubule arrays (cortical microtubules, PreProphaseBand microtubules, phragmoplast http://plants.trends.com
microtubules) located at the cell periphery control plant morphogenesis. Cytoplasmic arrays are involved in cargo movement within the cell and movement from cell to cell. Certain tubulin isotypes show tissue specificity and/or differential sensitivity to binding molecules. Taking all these characteristics into account, this book comprehensively covers potential approaches to transfer genes from one plant to another, thus avoiding the risks encountered using transgenes from heterologous organisms. Numerous examples of the introduction of desirable traits into agronomically important crops are given and new working models are proposed to investigate microtubule function. For example, certain tubulin genes are specifically induced in tissues such as anthers, roots or hypocotyls (Diego Brevario, Chapter 7) and their promotors can be used to target expression to these tissues. In tobacco and papaya roots, overexpression of citrate synthase improves microtubule tolerance to aluminium2. Such a strategy could increase worldwide crop yield because aluminium is abundant in soil (Mayandi Sivaguru et al., Chapter 5). Targeted expression could also be used to change the quality of wood by modifying the cell wall structure. Although the orientation of microtubules and microfibrils in the cell wall are not always linked and the mechanism responsible for the deposit of cellulose microfibrils is still under debate, it is possible that microtubule reorientation could alter cell wall structure. For example, plant hormones reorient cortical microtubules and increasing their expression changes their growth pattern (Ryo Funada, Chapter 3). Microtubule-associated proteins influence microtubule dynamics. Expressing microtubule-bundling genes under a tissue-specific promotor could reduce stem growth by stabilizing internode microtubules in the longitudinal orientation, thus giving the plant better lodging resistance. Targeting such genes to the base of leaf blades would improve leaf exposure to light and increase the efficiency of photosynthesis giving higher seed yield (Peter Nick, Chapters 1 and 2). In addition to tissue-specific expression, many stimuli such as cold,
light, heavy metals, hormones or pathogens transcriptionally regulate the expression of tubulin isotypes in different species. A modification of the level of expression of defined tubulin isotypes or mutants would avoid agronomical problems that occur as a result of biotic and abiotic stresses (Nick, Chapter 6; Vance Baird; Yaroslaw B. Blume and Susan M. Wick, Chapter 8). In rice, the level of the β-tubulin isotype TUB16 decreases when root elongation is blocked by anoxia3. Maintaining this isotype at a constant high level could overcome this problem. Certain point mutations in the tubulin sequence confer drug resistance. Transgenic maize cells expressing such genes are tolerant to herbicides4 and could be exploited to reduce herbicide use in the field (Kevin C. Vaughn, Chapter 9). Last but not least, viruses use the plant cytoskeleton for their propagation during infection5. Mutating the tubulin domain that interacts with viral proteins could block virus transmission (Issei Kobahashi and Yukko Kobayashi, Chapter 4). I highly recommend this book to fundamental and applied research scientists who will find valuable information herein on microtubule function and the use of microtubules as targets for research and development in biotechnology. Anne-Catherine Schmit Institut de Biologie Moléculaire des Plantes, 12, rue du général Zimmer, F-67084 Strasbourg-Cedex, France. e-mail: [email protected] References 1 Richter, L.J. et al. (2000) Production of hepatitis B surface antigen in transgenic plants for oral immunization. Nat. Biotechnol. 18, 1167–1171 2 De la Fuente, J.M. et al. (1997) Aluminum tolerance in transgenic plants by alteration of citrate synthesis. Science 276, 1566–1568 3 Giani, S. and Brevario, D. (1996) Rice β-tubulin mRNA levels are modulated during flower development and in response to external stimuli. Plant Sci. 116, 147–157 4 Anthony, R.G. and Hussey, P.J. (1999) Double mutation in eleusine indica α-tubulin increases the resistance of transgenic maize calli to dinitroaniline and phosphorothioamidate herbicides. Plant J. 18, 669–674 5 Boyko, V. et al. (2000) Function of microtubules in intercellular transport of plant virus RNA. Nat. Cell Biol. 2, 826–832
Forum
TRENDS in Plant Science Vol.6 No.4 April 2001
Book Review
Microtubules as ‘green fingers’ for crop improvement Plant Microtubules. Potential for Biotechnology Edited by Peter Nick. Springer-Verlag, 2000. DM149.00/£51.50/US$110.00 hbk (vi + 209 pages) ISBN 3 540 67105 6
At the dawn of the third millennium, the survival of the world’s poorest people is at stake. The challenge is to find the cheapest appropriate answers to enhance food quality, quantity and access. Using genetic engineering, or the so-called ‘green’ biotechnology, scientists are in the process of creating safe tools to modify plant genomes. Their aim is to produce more crops by enhancing their resistance to pathogens and to stress, better crops by increasing their nutrient value, and cheaper crops by reducing the need for pesticides and herbicides without yield loss. Plants can also be used as vaccination vectors because edible vaccines are a convenient and inexpensive way of immunizing against infectious diseases. For example, vaccines against hepatitis have been developed in banana1 and vaccines against cholera in potato. Plant Microtubules. Potential for Biotechnology is written by 12 authors, and deals with the biological mechanisms implicating microtubules and the potential role of microtubules in new strategies to raise yield ceilings by changing plant architecture. Because the cytoskeleton is involved in key mechanisms of plant growth and development, microtubules are a useful target for genetic, pharmacological or ecophysiological manipulation. Tubulins are encoded by multigene families and are ubiquitous in eukaryotes. Plant microtubules appear to have more functions than their animal counterparts. Specialized microtubule arrays (cortical microtubules, PreProphaseBand microtubules, phragmoplast http://plants.trends.com
microtubules) located at the cell periphery control plant morphogenesis. Cytoplasmic arrays are involved in cargo movement within the cell and movement from cell to cell. Certain tubulin isotypes show tissue specificity and/or differential sensitivity to binding molecules. Taking all these characteristics into account, this book comprehensively covers potential approaches to transfer genes from one plant to another, thus avoiding the risks encountered using transgenes from heterologous organisms. Numerous examples of the introduction of desirable traits into agronomically important crops are given and new working models are proposed to investigate microtubule function. For example, certain tubulin genes are specifically induced in tissues such as anthers, roots or hypocotyls (Diego Brevario, Chapter 7) and their promotors can be used to target expression to these tissues. In tobacco and papaya roots, overexpression of citrate synthase improves microtubule tolerance to aluminium2. Such a strategy could increase worldwide crop yield because aluminium is abundant in soil (Mayandi Sivaguru et al., Chapter 5). Targeted expression could also be used to change the quality of wood by modifying the cell wall structure. Although the orientation of microtubules and microfibrils in the cell wall are not always linked and the mechanism responsible for the deposit of cellulose microfibrils is still under debate, it is possible that microtubule reorientation could alter cell wall structure. For example, plant hormones reorient cortical microtubules and increasing their expression changes their growth pattern (Ryo Funada, Chapter 3). Microtubule-associated proteins influence microtubule dynamics. Expressing microtubule-bundling genes under a tissue-specific promotor could reduce stem growth by stabilizing internode microtubules in the longitudinal orientation, thus giving the plant better lodging resistance. Targeting such genes to the base of leaf blades would improve leaf exposure to light and increase the efficiency of photosynthesis giving higher seed yield (Peter Nick, Chapters 1 and 2). In addition to tissue-specific expression, many stimuli such as cold,
light, heavy metals, hormones or pathogens transcriptionally regulate the expression of tubulin isotypes in different species. A modification of the level of expression of defined tubulin isotypes or mutants would avoid agronomical problems that occur as a result of biotic and abiotic stresses (Nick, Chapter 6; Vance Baird; Yaroslaw B. Blume and Susan M. Wick, Chapter 8). In rice, the level of the β-tubulin isotype TUB16 decreases when root elongation is blocked by anoxia3. Maintaining this isotype at a constant high level could overcome this problem. Certain point mutations in the tubulin sequence confer drug resistance. Transgenic maize cells expressing such genes are tolerant to herbicides4 and could be exploited to reduce herbicide use in the field (Kevin C. Vaughn, Chapter 9). Last but not least, viruses use the plant cytoskeleton for their propagation during infection5. Mutating the tubulin domain that interacts with viral proteins could block virus transmission (Issei Kobahashi and Yukko Kobayashi, Chapter 4). I highly recommend this book to fundamental and applied research scientists who will find valuable information herein on microtubule function and the use of microtubules as targets for research and development in biotechnology. Anne-Catherine Schmit Institut de Biologie Moléculaire des Plantes, 12, rue du général Zimmer, F-67084 Strasbourg-Cedex, France. e-mail: [email protected] References 1 Richter, L.J. et al. (2000) Production of hepatitis B surface antigen in transgenic plants for oral immunization. Nat. Biotechnol. 18, 1167–1171 2 De la Fuente, J.M. et al. (1997) Aluminum tolerance in transgenic plants by alteration of citrate synthesis. Science 276, 1566–1568 3 Giani, S. and Brevario, D. (1996) Rice β-tubulin mRNA levels are modulated during flower development and in response to external stimuli. Plant Sci. 116, 147–157 4 Anthony, R.G. and Hussey, P.J. (1999) Double mutation in eleusine indica α-tubulin increases the resistance of transgenic maize calli to dinitroaniline and phosphorothioamidate herbicides. Plant J. 18, 669–674 5 Boyko, V. et al. (2000) Function of microtubules in intercellular transport of plant virus RNA. Nat. Cell Biol. 2, 826–832