Plant Genetic Engineering, 1991
Plant Biotechnology Series

Plant biotechnology offers important opportunities for agriculture, horticul­ ture, and the food industry by generating new transgenic crop varieties with altered properties. This is likely to change farming practices, improve the quality of fresh and processed plant products, and reduce the impact of food production on the environment. The purpose of this series is to review the basic science that underpins plant biotechnology and to show how this knowledge is being used in directed plant breeding. It is intended for those involved in fundamental and applied research on transgenic plants in the academic and commercial sectors. The first volume deals with plant genes, how they work, and their transfer from one organism to another. Authors discuss the production and evaluation of the first generation of transgenic crops resistant to insects, viruses and herbicides, and consider aspects of gene regulation and targeting of their protein products to the correct cellular location. All the contributors are actively engaged in research in plant biotechnology and several are concerned directly with its commercial applications. Their chapters highlight the importance of a fundamental understanding of plant physiology, biochemistry, and cell and molecular biology for the successful genetic engineering of plants. This interdisciplinary approach, which focuses research from traditionally separate areas, is the key to further developments which are considered in subsequent volumes. Don Grierson Contributors Alan B. Bennett Mann Laboratory, Department of Vegetable Crops, University of California, Davis, CA 95616 John W. s.

1 Plant gene structure and expression.- 1.1 Introduction.- 1.2 Protein-coding genes.- 1.2.1 Structure of protein-coding genes.- 1.3 Regulation of plant gene expression.- 1.3.1 Transcriptional regulation.- 1.3.2 DNA methylation.- 1.3.3 Post-transcriptional regulation.- 1.3.4 mRNA-processing.- 1.4 Translational control.- 1.5 Differential expression.- 1.5.1 Multigene families.- 1.5.2 Pseudogenes.- 1.6 RNA-coding genes.- 1.7 RNA genes transcribed by RNA polymerase I.- 1.8 RNA genes transcribed by RNA polymerase II.- 1.9 RNA genes transcribed by RNA polymerase III.- References.- 2 Gene transfer to plants.- 2.1 Introduction.- 2.1.1 General concepts.- 2.1.2 Target plant cells for transformation.- 2.1.3 Transformation vector considerations.- 2.2 Vectors based on the Agrobacterium Ti plasmid.- 2.2.1 The Ti plasmid as a natural plant transformation vehicle.- 2.2.2 The process of T-DNA transfer.- 2.2.3 Vectors based on the Ti plasmid.- 2.2.4 Transformation techniques using Agrobacterium vectors.- 2.3 Physical DNA delivery methods.- 2.3.1 Chemically stimulated plasmid uptake into protoplasts.- 2.3.2 Transformation of protoplasts by electroporation.- 2.3.3 Microinjection, ‘macromjection’ and microprojectiles.- 2.3.4 Virus vectors for gene transfer to plants.- 2.4 Uses of gene transfer technology.- 2.4.1 Properties of transformed plants.- 2.4.2 Plant variety improvement: addition of useful traits to crop species.- 2.4.3 Analysis of gene regulation and basic biochemical and molecular studies.- 2.4.4 Genetic mapping and gene cloning.- References.- 3 Developing herbicide resistance in crops by gene transfer technology.- 3.1 Introduction.- 3.2 Modification of the target of herbicide action.- 3.2.1 Glyphosate.- 3.2.2 Sulphonylureas and imidazolinones.- 3.2.3 L-Phosphinothricin.- 3.2.4 Atrazine.- 3.2.5 Conclusion.- 3.3 Detoxification or degradation of the herbicide.- 3.3.1 Plant detoxifying enzymes.- 3.3.2 Bacterial detoxifying enzymes.- 3.3.3 Conclusion.- 3.4 Perspectives.- References.- 4 Genetic engineering of plants for insect resistance.- 4.1 Introduction.- 4.1.1 Monoculture.- 4.1.2 Absence of inherent resistance.- 4.1.3 Agrochemicals.- 4.2 Defensive methods used by plants against insect attack.- 4.2.1 Defensive mechanisms and plant breeding.- 4.2.2 Insecticidal plant metabolites.- 4.3 Insecticidal compounds from other sources.- 4.3.1 Chemical insecticides.- 4.3.2 Bacterial toxins.- 4.3.3 Biological control.- 4.4 Constraints on the genetic engineering of plants for insect resistance.- 4.5 The production of insect-resistant transgenic plants: two case studies.- 4.5.1 Transgenic plants expressing Bt toxins.- 4.5.2 Transgenic plants expressing protease inhibitors.- 4.6 Future prospects.- References.- 5 Virus-resistant plants.- 5.1 Introduction.- 5.2 Basic concepts of resistance to plant virus infection.- 5.3 Key features of the infection cycles of positive-strand RNA plant viruses.- 5.3.1 Plant-to-plant spread of viruses.- 5.3.2 Virus entry, uncoating and early translation.- 5.3.3 Modes of gene expression.- 5.3.4 Replication of virus RNA.- 5.3.5 Virus assembly.- 5.3.6 Cell-to-cell and long-distance movement.- 5.4 Molecular bases and exploitation of naturally occurring virus resistance genes.- 5.4.1 Resistance operating by inhibition of virus replication in single cells.- 5.4.2 Resistance restricting virus cell-to-cell movement.- 5.4.3 Resistance mediated by induction of a host hypersensitive response.- 5.4.4 Prospects for cloning and manipulating naturally occurring virus resistance genes.- 5.5 Construction and expression of artificial resistance genes in transgenic plants.- 5.5.1 The cross-protection phenomenon as a source of potential resistance genes.- 5.5.2 Cross-protection in transgenic plants expressing a mild virus strain.- 5.5.3 Resistance in transgenic plants expressing virus coat protein genes.- 5.5.4 Disease attenuation in transgenic plants expressing satellite RNAs.- 5.5.5 The antisense RNA approach.- 5.5.6 Virus-resistant plants expressing sense RNA.- 5.5.7 Potential of ribozymes in the construction of artificial virus resistance genes.- 5.6 Future prospects.- References.- 6 Targeting of proteins to chloroplasts and mitochondria.- 6.1 Introduction.- 6.2 Structure and biogenesis of chloroplasts.- 6.3 Import of stromal proteins.- 6.3.1 Binding to import receptors in the chloroplast envelope.- 6.3.2 Translocation across the envelope membranes.- 6.3.3 Proteolytic maturation of imported stromal proteins.- 6.3.4 Structure and location of stroma-targeting signals.- 6.4 Transport of proteins into the thylakoid system.- 6.4.1 Biogenesis of thylakoid lumen proteins.- 6.4.2 Import and integration of the light-harvesting chlorophyll-binding protein.- 6.5 Import of proteins into the envelope membranes.- 6.6 Transport of proteins into mitochondria.- 6.6.1 Early stages in the import pathway.- 6.6.2 Transport across the mitochondrial membranes.- 6.6.3 Sorting of imported mitochondrial proteins.- 6.6.4 Transport of proteins into plant mitochondria.- References.- 7 Protein transport and targeting within the endomembrane system of plants.- 7.1 Introduction.- 7.2 Biogenesis of endomembrane compartments.- 7.2.1 Endoplasmic reticulum.- 7.2.2 Nuclear envelope.- 7.2.3 Golgi apparatus.- 7.2.4 Cell surface.- 7.2.5 Vacuole.- 7.2.6 Protein bodies.- 7.2.7 Lipid bodies.- 7.2.8 Peroxisomes.- 7.3 Mechanisms of protein transport.- 7.3.1 Endoplasmic reticulum entry.- 7.3.2 Endoplasmic reticulum-to-Golgi transport.- 7.3.3 Intra-Golgi transport.- 7.3.4 Post-Golgi transport.- 7.4 Mechanisms of protein sorting.- 7.4.1 Endoplasmic reticulum entry—the signal sequence.- 7.4.2 Endoplasmic reticulum retention.- 7.4.3 Secretion.- 7.4.4 Protein body/vacuole localisation.- 7.4.5 Peroxisome localization.- 7.5 Glycosylation and post-translational modification.- 7.5.1 N-linked glycosylation.- 7.5.2 O-linked glycosylation.- 7.5.3 Proteolytic processing.- 7.5.4 Other post-translational modifications.- References.- 8 Identification and characterisation of tissue-specific genes from flowers.- 8.1 Introduction.- 8.2 Identification of flower-specific genes.- 8.3 Characterisation of gene expression in floral organs.- 8.4 Tissue and cell specificity of gene expression in flowers.- 8.5 Discussion.- References.